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PEOCEEDINGS

AND

TRANSACTIONS

OF THE

LIVERPOOL BIOLOGICAL SOCIETY.

VOL. XXIV.

SESSION 1909-1910.

LIVERPOOL :

C. Tinling & Co., Ltd., Peinters, 53, Victoria Street.

19 10.

yj

CONTENTS.

SIOJ^

L\^

\J 5.-'^

(W-0
■ M

I. — Proceedings.

PAGE

Office-bearers and Council, 1909-1910 . . . vii.

Report of the Council ...... viii.

Summary of Proceedings at the Meetings . . ix.

List of Members ....... xiii.

Treasurer’s Balance Sheet ..... xvii.

II. — Transactions.

Presidential Address — “ Some notes on the Natural
History of Jamaica.” By R. Newstead, M.Sc.,

A.L.S 1

Twenty-third Annual Report of the Liverpool Marine
Biological Committee and their Biological Station
at Port Erin. By Prof. W. A. Herdman, D.Sc.,

F.R.S 3 ^

Report on the Investigations carried on during 1909,
in connection with the Lancashire Sea-Fisheries
Laboratory, at the University of Liverpool, and
the Sea-Fish Hatchery at Piel, near Barrow ;

By Prof. W. A. Herdman, D.Sc., F.R.S., Andrew
Scott, A.L.S., and James Johnstone, B.Sc.

63^

PEOCEEDINGS

OF THE

LIVERPOOL BIOLOGICAL SOCIETY.

OFFICE -BEAKERS AND COUNCIL.

1886— 57 Prof. W. MITCHELL BANKS, M.D., F.R.C.S.

1887— 88 J. J. DRYSDALE, M.D.

1888— 89 Prof. W. A. HERDMAN, D.Sc., E.R.S.E.

1889— 90 Prof. W. A. HERDMAN, D.Sc., E.R.S.E.

1890— 91 T. J. MOORE, C.M.Z.S.

1891— 92 T. J. MOORE, C.M.Z.S.

1892— 93 ALFRED 0. WALKER, J.P., F.L.S.

1893— 94 JOHN NEWTON, M.R.C.S.

1894— 95 Prof. F. GOTCH, M.A., F.R.S.

1895— 96 Prof. R. J. HARVEY GIBSON, M.A.

1896— 97 HENRY O. FORBES, LL.D., F.Z.S.

1897— 98 ISAAC C. THOMPSON, F.L.S. , F.R.M.S.

1898— 99 Prof. C. S. SHERRINGTON, M.D., F.R.S.

1899— 1900 J. WIGLESWORTH, M.D., F.R.C.P.

1900— 1901 Prof. PATERSON, M.D., M.R.C.S.

1901— 1902 HENRY C. BEASLEY.

1902— 1903 R. CATON, M.D., F.R.C.P.

1903— 1904 Rev. T. S. LEA, M.A.

1904— 1905 ALFRED LEICESTER.

1905— 1906 JOSEPH LOMAS, F.G.S.

1906— 1907 Prof. W. A. HERDMAN, D.Sc., F.R.S.

1907— 1908 W. T. HAYDON, F.L.S.

1908— 1909 Prof. B. MOORE, M.A., D.Sc.

SESSION XXIV., 1909-1910.

^r^stbent :

R. NEWSTEAD, M.Sc., A.L.S.

W. T. HAYDON, F.L.S.

Prof. B. MOORE, M.A.., D.Sc.

||oii. poit. librarian:

W. J. HALLS. MAY ALLEN, B.A.

^0iL .Secritaxg:

JOSEPH A. CLUBB, D.Sc.

^iouiuil:

HENRY C. BEASLEY.

J. JOHNSTONE, B.Sc.

OULTON HARRISON.

Prof. HERDMx\N, D.Sc., F.R.S.
DOUGLAS LAURIE, M.A.

W. S. LAVEROCK, M.A., B.Sc.

J. H. O’CONNELL, L.R.C.P.
Prof. PATERSON, M.D.
JOSEPH PEARSON, D.Sc.
Prof. SHERRINGTON, F.R.S.
E. THOMPSON.

L. R. THORNELY (Miss

Representative of Students Section :

E. M. BLACKWELL (Miss).

Vlll

LIVEUPOOL BIOLOGICAL SOCIETY.

*

REPORT of the COUNCIL.

lIuuiNG the Session 19U9-10 there have been seven
ordinary meetings and one field meeting of the Society.

The communications made to the Society at the
ordinary meetings have been representative of almost all
branches of Biology, and the various exhibitions and
demonstrations tliereon have been of great interest.

By invitation of the Council, Prof. J. H. Ealkner
Nuttall, E.R.S., of Cambridge, lectured before the
Society, at the December Meeting, on “ Ticks, and their
relation to disease.”

The Library continues to make satisfactory progress,
and additional important changes have been arranged.

The Treasurer’s statement and balance-sheet are
appended.

Tlie members at present on the roll are as follows : —
Ordinary members ------ 46

Associate members ------ 3

Student members, including Students’ Section - 32

Total

81

SUMMARY OF PROCEEDINGS AT MEETINGS.

IX

SUMMARY of PROCEEDINGS at the MEETINGS.

The first meeting of the twenty-fourth session was
held at the University, on Friday, October I5th, 1909.

The President-elect (R. Newstead, M.Sc., A.L.S.j
took the chair in the Zoology Theatre.

1. The Report of the Council on the Session 1908-1909

(see " Proceedings,” Yol. XXIII., p. viii.) was
submitted and adopted.

2. The Treasurer’s Balance Sheet for the Session 1908-

1909 (see Proceedings,” t ol. XXIII., p. xviii.)
was submitted and approved.

d. The following Office-bearers and Council for the
ensuing Session were elected: — Vice-Presidents,
A\ . T. Tlaydon, F.L.S., and Prof. B. Moore, D.Sc. ;
Hon. Treasurer, W. J. Halls; Hon. Librarian,
May Allen, B.A. ; Hon. Secretary, Joseph

A. Clubb, D.Sc. ; Council, IT. C. Beasley,
T. Johnstone, -B.Sc., Oulton Harrison, Prof.
Herdman, D.Sc., F.R.S., W. S. Laverock, M.A.,

B. Sc., Douglas Laurie, M.A., J. II. O’Connell,
L.R.C.P., Prof. Paterson, M.D., Joseph Pearson,
D.Sc., Prof. Sherrington, F.R.S., E. Thompson,
and (Missj L. R. Thornely.

4. R. Newstead, M.Sc., A.L.S., delivered the Presidential
Address on “ Some notes on the Natural History
of Jamaica” (see ” Transactions,” p. 1). On the
motion of Dr. O’Connell, a vote of thanks was
carried with acclamation.

X

LIVERPOOL BIOLOGICAL SOCIETY.

The second meeting of the twenty-fourth session was
held at the University, on Friday, jS’oveinher 12th, 1909.,
The President in the chair.

1. Dr. Cliihb reported the capture of a young Urey Seal

{Halich(crus gnypus), stranded at Hoylake, and
that the specimen was still living in tlie tanks in
the Liverpool Museum Aquarium. This is the
third record of this species for this neighbourhood.

2. Prof. Ilerdman submitted the Annual Report on the

work of the Livei‘])ool Marine Biology Committee
and the Port Erin Biological Station (see
“Transactions,” p. 3).

The third meeting of the twenty-fourth session was
held at the University, on Tuesday, December 14th, 1909.
The President in the chair.

1. Prof. J. H. Falkner Auttall, F.R.S., of Cambridge,
gave a lecture on “ Ticks, and tlieir relation to
disease.” The lecture was of great interest, and
was illustrated by a number of original lantern
slides. A cordial vote of thanks was passed on
the motion of Prof. Herdman.

The fourth meeting of the twenty-fourth session was
held at the University, on Friday, January 14th, 1910.

1. On the motion of the President, seconded by Prof.
Herdman, the cordial congratulations of the
Society were accorded to the members of the
Liverpool Geological Society on the attainment of
their Jubilee.

SUMMARY OF FROCEEDINGS At MEETINGS. XI

2. Mr. J. -Tolinstone, B.Sc., submitted the ‘Annual

Iteport of the Investigations carried on during
1909 in connection with the Lancashire Sea
Fisheries Committee (see “Transactions,” p. 63).

3. Dr. Bassett supplemented the above Deport by a

description of his work on “ The Salinity of the
Irish Sea area.”

The fifth meeting of the twenty-fourth session was
held at the University, on Friday, February 11th, 1910.
The President in the chair.

1. Mr. Edwin Thompson gave an interesting account,
illustrated by apparatus, of his work in Photo-
micrography.

The sixth meeting of the twenty-fourth session was
held at the University, on Friday, March 11th, 1910.
The Vice-President (Mr. W. T. Ha3Mon) in the chair.

1. The following exhibits, with demonstrations, were

made : —

(a) Living Boas and Pythons, by Dr. O’Coilnell.

(h) Living Stick Insects [Bacillus rossii), by
Dr. Clubb.

(c) Specimens and apparatus from the Zoological
Laboratories, b}^ Prof. Herdman and Dr.
Pearson.

2. Dr. H. E. Poaf submitted a paper on the “ Physiology

of Marine Invertebrates,” dealing specially Avith
the digestive ferments.

Xll

LIVERPOOL RIOLOGICAL SOCIETY.

The seventh meeting of the twenty-fourth session
was held at the Universily, on Friday, May Otli, 11)10.
The President in the chair.

1. Dr. d. Travis Jenkins, Superintendent of Fisheries
to the Lancashire County Council, gave a lecture
on Fishery Enquiries in Bengal,” illustrated hy
a series of lantern slides prepared from tlic
lecturer’s negatives.

The eighth meeting of the twenty-fourth session was
tlie Ajinual Field Meeting held at Delamere Forest, on
Saturday, June 11th. Mr. Pobert Newstead kindly
acted as leader. At the short business meeting held after
tea, on the motion of Prof. Ilerdman, Mr. IC Aewstead,
M.Sc., A.L.S., was unanimously re-elected President tor
the ensuing session.

LIST of MEMBEES of the LIVEEPOOL
BIOLOGICAL SOCIETY.

SESSION 1909-1910.

A. Ordinary Members.

(Life Members are marked with an asterisk.)

ELECTED.

1908 Abram, Prof. J. Hill, 74, Rodney Street,

Liverpool.

1909 '*^Allen, Miss May, B.A., Hon. Librarian, Natural

History Department, University.

1888 Beasley, Henry C., Prince Alfred Road.

Wavertree.

1908 Bigland, H. D., B.A., Shrewsbury Road,

Birkenhead.

1903 Booth, jun., Chas., 30, James Street, Liverpool.
1886 Caton, R., M.D., F.RiC.P., 78, Rodney Street.

1886 Clubb, J. A., D.Sc., Hon. Secretary, Free Public
Museums, Liverpool.

1902 Glynn, Dr. Ernest, 67, Rodney Street.

1903 Guthrie, Dr. Thomas, 9, Canning Street,

Liverpool.

1886 Halls, W. J., Hon. Treasurer, 35, Lord Street.

1896 Haydon, W. T., F.L.S., Yice-President, 55,

Grey Road, Walton, Liverpool.

1886 Herdman, Prof. W. A., D.Sc., F.R.S.,
University, Liverpool.

1893 Herdman, Mrs. W. A., Croxteth Lodge, Ullet
Road, Liverpool.

1897 Holt, Alfred, Crofton, Aigburth.

1902 Holt, A., jun., Crofton, Aigburth,

XIV

LIVERPOOL BIOLOGICAL SOCIETY.

1903 Holt, George, 5, Fulwood Park, Liverpool.

1903 Holt, Pickard D., M.P., 1, India Buildings, Liver-

pool.

1898 Johnstone, James, B.8c., University, Liverpool.
1908 Jones,- John Share, F.P.C.V.S., Yet. Hepartment,
University, Liverpool.

1894 Lea, Pev. T. S., M.A., Tlie Yiccarage, St. Austell,
Cornwall.

1890 Laverock, W. S., M.A., B.Sc., Free Museums,
Liverpool.

1906 Laurie, P. Douglas, M.A., University, Liverpool.
1905 Moore, Prof. B., Vice-President, University,
Liverpool.

1908 Myres, Prof. J. L., University, Liverpool.

1904 Aewstead, P., M.Sc., A.L.S., Pkestdent, Sdiool

of Tropical Medicine, Liverpool.

1904 O’Connell, Dr. J. II., 38, Heathfield Poad,
Liverpool.

1904 Pallis, Miss M., Tatoi, Aigbnrth Drive, Liverpool
1894 Paterson, Prof., M.D., M.P.C.S., University,

Liverpool.

1894 Paul, Prof. F. T., 38, Podney Street, Liverpool.

1905 Pearson, J., D.Sc., Zoological Department,

Liverpool.

1903 Petrie, Sir Charles, 7, Devonshire Poad, Liverpool.
1903 Pathbone, H. P., Oakwood, Aigburth.

1890 "^Pathbone, Miss May, Backwood, Neston.

1909 Poaf, Dr. H. E., Physiological Department,

University, Liverpool.

1897 Pohinson, IT. C., Ylalay States.

1908 Pock, W. II., 25, Lord Street, Liverpool.

1894 Scott, Andrew, A.L.S., Piel, Barrow-in-Furness.

1895 Sherrington, Prof., 5LD., F.P.S., University,

Liverpool,

LIST OF MEMBERS.

XV

1886 Smith, Andrew T., 5, Hargreaves Eoad, Sefton
Park.

1908 Stapledon, W. C., 2, Marine Park, West Kirbv.

1903 Thomas, Hr. Thelwall, 84, Eodney Street,

Liverpool.

1905 Thompson, Edwin, 1, Croxteth Grove, Liverpool.

1889 Thornely, Miss L. E., Nimclose, Grassendale.

1888 Toll, J. M., 49, Tsewsham Drive, Liverpool.

1891 Wiglesworth, T., M.D., E.E.C.P., Connty Asylum,
Eainhill.

1909 AVliitley, Edward, Cloveliy, Sefton Park,

Liverpool.

B Associate Members.

1903 Tattersall, W., B.Se., The Miiseums, Manchester.

1905 Harrison, Oulton, Denehnrst, Victoria Park,
Waver tree.

1905 Carstairs, Miss, 39, Lilley Eoad, Fairfield.

C University Students’ Section.

President: E. M. Blackwell (Miss).

Hon. Secretary: G. A. Jackson (Miss).

Members :

The Misses G. Jackson, M. Jolley, M. Scott, D. Lawson,
F. Uttley, A. Wildman, E. Horsman, L. Gleave,
E. Eobbins, E. Bamber, M. Firth, Y. Gill, Black-
ledge, M. Heap, A. B. Dixon, E. Bland, A. Lennon,
A. Lee, H. Coburn, M. Latarche, E. M. Blackwell,
C. Beardsworth, Stubbs, Edge, G. Eobinson, Hollins-
head, Knight, Messrs. Waterhouse, Weston, Jackson,
Nelson, Danier,

XVI

LIVERPOOL BIOLOGICAL SOCIETY.

D Honorary Members.

S.A.S., Albert I,, Prince de Monaco, 10, Avenue du
brocadero, Paris.

Bornet, Dr. Edouard, Quai de la Tournelle 27, Paris.
Claus, Prof. .Carl, University, Vienna.

Fritscb, Prof. Anton, Museum, Prague, Bohemia.
Haeckel, Prof. Dr. E., University, Jena.

Hanitscli, P., Ph.D., Baffles Museum, Singapore.
Solms-Laubach, Prof.-Dr., Botan. Instit., Strassburg.

THE LIVERPOOL BIOLOGICAL SOCIETY

In Account with W. J. HALLS, Hon. Treasurer.

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Liverpool, October 7th, 1910. HENEY C. BEASLEY.

TEANSACTIONS

OF THE

LIVERPOOL BIOLOGICAL SOCIETY.

INAUGUEAL ADDEESS

ON

THE NATUEAL HISTOEY OF JAMAICA.

By EOBEET NEWSTEAD, M.Sc., A.L.S., etc.,

PRESIDENT.

[Abstract.]

Ill liis opening remarks the President expressed his
warmest thanks to the Members of the Liverpool
Biological Society for the distinguished honour which
they had conferred upon liinY in electing him to the
Presidential chair for the ensuing year. In recalling the
names of the eminent men who had filled the office in
previous years, he felt somewhat diffident in accepting
the position which the members had bestowed upon him
with such flattering cordiality.

The subject matter of the President’s address was
based upon experiences gained during a stay in the Island
of Jamaica in the winter of 1908-9, while on a special
expedition sent out by the Liverpool School of Tropical
Medicine to study certain problems connected with
tick-borne diseases in cattle, and also other pests
connected with agriculture, etc.

After briefly discussing the physical features of the
country and its chief geological characters, some of the
more striking plant-forms were described, among which
the curious Epiphytes (Bromeliaceae, etc.), the parasitic
plants (Cuscuta, etc.), and some of the beautiful legumes
may be mentioned. Some observations relating to the
insect fauna of Jamaica were of interest from a
bionomical point of view.

2 TKANSAcnoNS LivEiirooJ. i5]OJ.O(;r::JAJ. socieiy.

Ill dealing with the natural enemies ot ea tile-ticks
(Ixodoidea), special reference was made to the dietary of
the Horn-billed Cuckoo (Crotoj)ha(ja ani), a bird which
appeared to exercise little or no choice in the selection of
its food, nauseous plant-bugs being eaten apparently
just as freely as those insects which belong to the
so-called edible group. In a series of post-mortem
examinations many ticks were found in the contents of
the stomachs; also many examples of the green
“stink-bug” {Loxa flavicollis). This bug, whose odour
is horribly offensive, does not possess any warning
coloration; but being of a uniformly green colour is
highly protected and difficult to discover when resting
among the leafy branches of a tree or shrub. Tbe amount
of odoriferous matter contained in the stomachs of the
birds found to contain the remains of this bug were so
offensive as to render the operation of dissection
positively unbearable, and the foetid odour was with
difficulty removed from the hands of the operator. The
common “cotton stainer” {Dysderciis sp.), an hemipteron
with a markedly warning orange-red colour pattern;
nests of the paper-building wasp (Folistes crinita); huge
black “witch moths” (Erebus argarista), measuring
nearly six inches in the wing expanse; Geodephagous
and Chrysomelid beetles ; molluscs and berries ; all of
these were found to have been eaten by this bird.

In referring to the work of the Expedition, the
President said that he was happy to be able to state that
the practical experiments which he had conducted
indicated that a most effective means of controlling
cattle-ticks had been devised, and that highly satisfactory
reports had been received from the Government in
confirmation of this statement.

3

THE

MARINE BIOLOGICAL STATION AT PORT ERIN,

BEING THE

TWENTY-THIRD ANNUAL REPORT

OF THE

LIVERPOOL MARINE BIOLOGY COMMITTEE.

We have again to record a serious loss in the death of
Mr, Lomas, an active and much valued member of the
Committee, who was killed in a railway accident in the
Algerian desert on the way to Biskra, on December 17th
1908.

Joseph Lomas, F.G.S., came to Liverpool from the
Royal College of Science and School of Mines, South
Kensington, where he had been a pupil of Huxley, Judd,
Howes, Scott, and other famous teachers. He joined
University College as a research student in 1885, and
his first research in our laboratories was zoological —
although it had a geological bearing too — being on the
marine polyzoa, and especially those that build up lime-
stone colonies often found fossil in the rocks. In fact, I
think it is the case that throughout his original work the
borderland between the two sciences, or rather the
applications of zoological knowledge to the interpretation
of geological appearances, had a special attraction
for Lomas; and that, no doubt, accounted for his
enthusiastic support of the Biological Society and the
Liverpool Marine Biology Committee, and his helpful
participation in our submarine explorations. His special
function on these expeditions was to collect, examine,
and report upon the nature and origin of the various
deposits now being formed on the sea bottom, and to
compare them with the more ancient ones that have

4 TRANSACTIONS LIVERPOOL RIOLOGICAL SOCIETY.

consolidated into the stratitied rocks of the glol)e.
vSeveral of his piihiished papers deal with such collections,
and a series of the floor deposits of the Irish Sea, formed
and classified under his guidance, is to be found not only
in our own University Museum of Zoology, but also in
the Museum of the Geological Survey at Jermyn Street,
London.

Although in the main a geologist, Lomas often took
part in our Biological expeditions, and frequently visited
the Port Erin Station. Tie wrote a detailed report on
the Polyzoa for the first volume of our Fauna,” and
occasionally named series of specimens or wrote short
notes for these Annual Peports. He was added to the
(^ommittee last November, just before he started on his
fatal expedition to the Sahara. Most of his papers
have, how^ever, been Geological, and have appropriately
dealt with the Triassic rocks of Lancashire and Cheshire,
and Lomas had for several years recently been the
secretary of a Trias Committee ” of the British
Association, which has produced annual reports upon the
extraordinary reptilian footprints and other remains
found in profusion in certain beds exposed periodically
by the quarrying operations at Storeton and elsewhere in
the district. Lomas kept a watchful eye upon the
progress of all such excavations, and it is due to his care
and knowledge, and to his happy knack of interesting
others in what he was studying, that many of the finest
slabs of Cheirotheroid footprints have been saved from
the quarry men and are now’ preserved in our museums.
Others of his papers and reports have dealt with glacial
phenomena and with more recent changes in the
configuration of the country (such as The Coasts of
Lancashire and Cheshire: their forms and origin’),

while some have been of wider scope, such as his addresses

MARINE BIOLOGICAL STATION AT PORT ERIN.

5

on tlie primeval rocks of the earth’s crust, and upon
‘‘ Comparative Lithology.” But it is impossible now
even to enumerate his various contributions to knowledge.
All have been good, and though it cannot be claimed
that Lomas has made any very great discovery, he has
done much useful original work, carefully detailed and
honestly set down. His reputation as a scientific man
has been steadily growing amongst scientific men outside
Liverpool, and for several years he has acted with marked
success as the chief secretary of Section C (Greology) of
the British i\.ssociation.

Lomas was fortunate in obtaining grants from
scientific funds, on occasions, to aid in his special
investigations, and it was on such a journey — to inquire
into the desert conditions in the neighbourhood of Biskra,
with a view to a comparison with the Triassic rocks upon
which Liverpool is built, and towards the expenses of
which he had applied for and received a grant from the
British Association at Dublin — that his useful life was
prematurely cut short last December. As in the case of
many another scientific man, his death came directly in
the course of his scientific investigations.

For many years Lomas gave special courses of
lectures on Geology and Physical Geography in the
University. This volunteer teaching work, although
sometimes it must have been heavy enough, was a labour
of love, and was hardly, I fear, remunerative, llis chief
reward must have been the consciousness of the good
work he was doing, and the gratitude of his students —
several of whom have themselves become geologists.

Most of those who have worked with him will,
however, agree that Lomas was at his best in ‘‘ the field ”
on geological or biological expeditions. He was pre-
eminently an open-air student of nature, and he could

6

TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

lead a party over the country all day, and day after day,
impressing upon them in the happiest manner both the
minutiae of rocks and fossils and the broad features of
stratification and mountain building, or water drainage
and the connection between landscape and geological
structure. Many of us have recollections that will never
fade of such days in Wales, or the Isle of Man, in the
Lake Country, on the Yorkshire moors, and even in far
South Africa. And beyond the earth- lore and all else
that he taught us then and at other times, we shall ever
remember the constant good nature and cheerful deter-
mination to make the best of everything, the helpful
resourcefulness in times of difficulty, and the honest
reliability and general sterling, lovable character of the
friend we have lost.

I would again point out that, in view of the loss of
so many of their old fellow- workers and supporters in the
last year or two, the Committee are most anxious to get
some younger men as recruits to fill the places thus left
vacant, both as actual workers in the field and also as
subscribers to the funds. There are now plenty of
students — in fact, during the Easter vacation the
Biological Station has, for the last few years, been
practically full — and there are plenty of young pro-
fessional researchers; but we have very few left of the
earnest amateur naturalists who were our main support
in the early days twenty years ago. The place left
vacant on the Committee by the death of Mr. Lomas has
been filled by the election of Dr. Benjamin Moore,
Professor of Bio-Chemistry in the University of Liverpool.
Professor Moore has for several years taken a keen interest

MARINE BIOLOGICAL STATION AT PORT ERIN.

7

in tlie work of the Committee. He has on several
occasions carried on research in vacations at the Port Erin
Station, and in association with Mr. E. Whitley and
Dr. H. E. Eoaf has developed a new side to our work,
viz., Bio-Chemistry and Comparative Physiology — a side
of biological investigation which is most appropriate to a
marine laboratory, and one which will probably be
actively pursued in the future.

Fia. 1. — S.Y. “ Ladybird,” on a Plankton cruise at Easter, 1908,
from a photo by Edwin Thompson.

The dredging, tow-netting and other investigationa
at sea, started two years ago with the yacht “ Ladybird,”
have been carried on vigorously during the Easter and
Summer vacations of 1909. Nearly 800 samples of
plankton have been collected with various nets in the
seas around Port Erin and have been sent to Mr. Andrew

8

TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Scott for microscopic investigation. During the Easter
vacation Mr. AV. liiddell, ALA., of Belfast, again gave
me most valuable assistance in taking daily Plankton
observations from ihe yacht. Air. W. J. Dakin at the
same time took charge of the corresponding Hydrographic
work, and Mr. W. Gunn, from the Liverpool Laboratory,
also gave efficient helj). Some account of the results of
these observations, and of the objects and methods of
plankton-Avork in general, will be found further on in
this Deport.

Fig. 2. — The Biological Station and Fish Hatchery at Port Erin,
from a photo by Edwin Thompson .

Our Hon. Treasurer, Air. E. Thompson, at Easter,
and Dr. E. AVard in Summer, were engaged in Photo-
micrograj)hic study of developing hsh embryos and other
subjects. I am indebted to both these friends for
beautiful photographs, from which some of the illustra-
tions in this Deport have been prepared.

The fish and lobster hatching, carried on for the
Isle of Man Fisheries Board, will be found reported

MARINE BIOLOGICAL STATION AT PORT ERIN.

9

on in detail below. Judged by the number of summer
visitors, this bas been a poor year in the Isle of Man
generally, and as a natural consequence our numbers in
the Aquarium record have fallen. We consider that under
the circumstances we liave not done badly in having
between thirteen and fourteen thousand visitors who paid
tor admission. The institution, it will be remembered, is
carried on jointly with the Fisheries Board, the receipts
and the expenses being shared equally with that Authority.

As on previous occasions, Mr. Chadwick has supplied
a “ Curator's lleport,” which will be found below, and he
has also, as usual, supplied me with details for some
other parts of this Iteport.

Fort}^ naturalists and students have occupied the
work-tables in the Laboratories for varying periods
during the year, as follows : —

The Station Ivecord.

Dec. 2Sth to Jan. 9th.

Feb. 20th to 22nd.

March 20th to April 21th.

Professor Herdinan. — Official.
Professor Herdman. — Official.
Professor Herdman. — Plankton.
Mr. W. Riddell. — Plankton.

Mr. W. J. Dakin. — Sense organs of Mollusca.

April Zrd to 20th.
April Sth to I2th.
April lOth to 26th.
April mh to 21th.

Dr. H. E. Roaf. — Physiology.

Mr. E. Thompson. — Photomicrography.

Mr. W. Gunn. — General.

Mr. R. D. Laurie. — Educational.

April IMh to 22nd.
A pril Uth to 21th.
April IMh to 21th.

Mr. Billington. — General.

Mr. Johnson. — General.

Miss E. M. Blackwell.
Miss A. B. Dixon.

Miss K. Winston.

Miss M. M. Heap.

Miss E. Matthewmaii.
Miss E. Bland.

Miss M. Scott.

Miss Prescott.

Miss L. W. Whitehurst.

Dr. Pearson. — Educational.
Mr. H. G. Jackson.
Miss M. Latarche.
Miss A. Lee.

Miss A. G. Wildman.
Miss F. Uttley.

Miss M. Southerst.
Miss E. Horsman.
Miss A. Lennon.

Miss T. A. Smith,
b. Miss D. LaAVson.

10 TRANSACTIONS

LIVERPOOL BIOLOGICAL SOCIETY.

April 2Qih to Tird
May VMh to J title \Hth.
July 1th to Aug. dth.
July 1th to A ug. VMh.

J uly l\th to 2Srd.

J uly 2Uh to Aug. \Uh.

J uly 21th to Sept. 10^/i.
July 3l5i to August \Mh.
Aug. Is^ to \2th.

Sept. 4th to I4th.

Sept. 4th to Oct. 2tid.

Sept. 21th to SOth.

Sept, and Oct. {occasional
Not). 2dth to Dec. 11th.

Mr. R. Williams Ellis. — General.

Dr. Ward. — Pliotograi)hy of living Fishes.

Mr. F. H. Gravely. — Polychaela.

Mr. S. Garside. — Marine Algae.

Mr. Pryce. — General.

MissC. E. Wetherall. — PolycliaetaandTiinicata.
Dr. Id. E. lioaf. — Physiology of Invertebrates.
Mr. W. A. Gunn. — General.

Professor Herdjuan. — Plankton.

Mr. T. J. Evans. — General.

Dr. H. Henry. — Haeinofiagellates of Fishes.
Miss Wilkinson. — Crustacea.
visits) IMr. C. Okcll. — General.

Miss B. Watterson. — General.

The “ Tables ” in the Laboratory were occupied as
follows : —

Liverpool University Table : —
Prof. Herdman.

Dr. Roaf.

Dr. Pearson.

]\Ir. Laurie.

iMr. Dakin.

JMr. Gunn.

Mr. Billington.

Miss B. Watterson.

Liverpool Marine Biology Convmittee 2
Mr. E. Thompson.

Dr. Ward.

Dr. Henry.

Mr. C. Okell.

^able : —

Mr. R. Williams Ellis.
Mr. Pryce.

Mr. Evans.

Mr. Riddell.

Manchester University Table : —

Mr. Gravely. ]\Ir. Garside.

Mr. Johnson. iMiss Wilkinson.

Birmingham University 2'able
Miss Wetherall.

The folloAving- students of Liverpool University
occupied the Junior Laboratory for a fortnight during the
Easter vacation, and worked together under the super-
vision of Professor Herdman, I)r. Pearson and Mr.
Laurie : —

Miss Lawson,
^liss Whitehurst.
Miss Smith.

Miss Prescott.
Miss Lennon.
Miss Scott.

Miss Horsman.

Miss Bland.

Miss Southerst.
Miss Matthewman.
Miss Uttley.

Miss Heap.

Miss Wildman.
Miss Winston.

Miss Lee.

Miss Dixon.
Miss Latarche.
Miss Blackwell.
Mr. Jackson.

MARINE BIOLOGICAL STATION AT PORT ERIN.

11

Curator’s Ixeport.

Mr. Chadwick reports as follows : —

“ The scientific work of the past year has been marked
by some increase in the number of workers in our
laboratories, and of researches which involved longer
periods of time and more extensive use ot the facilities
afforded by the Station and its equipment. The Easter
vacation class-work was again completely successful, and
showed the advantage of a number of students working-
together under competent guidance and within easy reach
of abundance of living material. Amongst the twenty-
nine students and researchers who occupied tables during
the year there were representatives of the Universities ot
Cambridge, Liverpool, Manchester, Birmingham and
Sheffield.

“ During the winter much time was devoted to
careful revision and remounting of museum specimens.
The whole of the collection of Molluscan shells was thus
dealt with, and some new specimens were added.

“ The study of Marine Plankton has again figured
largely in the year’s work. Tow-nettings have been taken
twice a week, over a prescribed course in the bay, with as
much regularity as the weather would permit, and a
larger share in the laborious work of estimation and
qualitative analysis of the gatherings has been under-
taken by the Curator.

“ The number of visitors to the Aquarium, compared
with the records of the previous two years, shows a con-
siderable falling oh. This was clearly due to the fact
that the Isle of Man as a whole did not enjoy its usual
measure of patronage during the visitors’ season. The
tanks were as well stocked as in previous years, and there

12 TRANSACTIONS LIVERPOOL RIOLOGICAL SOCIETY.

was no indication of waning interest on the part of the
13,500 visitors who paid for admission. The nnml)er of
copies of the ‘ Guide to the Aquarium ’ sold also shows
a considerable falling otf. We have abundant evidence,
however, that this ‘ Guide ’ has been regarded by many
visitors as a welcome addition to the popular literature
of Marine Biology.

“ Owing to the continued growth of living organisms
in the circulation pipes, to which reference w*as made in
last year’s Iteport, it was found necessary to take down
and thoroughly clean the whole system. This was done
during the months of November and December, 1908;
and at some points, especially the bends, the bore of the
pipe was found to be almost completely obstructed by
colonies of barnayles, mussels, and other molluscs. Before
re-erection the lengths of piping were provided with
flanges at their ends, so that it is now possible to remove
and clean any length without disturbing the neighbouring
ones.

“ The tanks have been maintained in excellent con-
dition by the Assistant Curator, and the mortality
amongst the fishes and invertebrates has been quite
insignificant. The largest conger has now been an
inhabitant of the aquarium for nearly 4^ years, and has
attained a length of exactly G feet.* Another specimen,
about 4 feet long, is the ‘ oldest inhabitant,’ having
occupied the same tank for over five years.

“ The hatching season of 1909 fully justified the
anticipation expressed by the Curator in last year’s
lieport. The number of plaice larvae hatched and
liberated, 7,124,500, was nearly double that of the
previous year, and brings the total number for the six

- This fish died on Fi iday, December 3rd. Its length was exactly
6 feet ; maximum girth, 2 feet ; weight, 59| lbs.

MARINE BIOLOGICAL STATION AT PORT ERIN.

13

years during wliicli the liatchery has been in operation
to twenty-five and a half millions.

Fig. 3. — Mr. T. Cregeen collecting fish eggs from the surface of the
spawning pond, from a photo by Edw'in Thompson.

“The numbers of eggs collected and of larvse set free

during the

season were as follows:

: —

Eggs collected.

Date. Larvae set free.

Date.

90,500

. . February 22 — 26

78,000 ...

March 22

253,500 ..

February 27 — March 3

184,500 ...

27

218,000 ..

, . March 4 and 5

148,000 ...

29

179,000 ..

,, 6 and 8

146,000 ...

5?

30

196,000 ..

„• 9 to 12

126,000 ...

>>

31

957,000 ..

„ 13 to 17

766,500 ...

April

5

737,000 ..

„ 18 to 20

609,000 ...

5?

8

732,000 ..

,,22 and 23

603,000 ...

10

545,000 ..

„ 24 to 26

400,000 ...

>>

13

391,500 ..

. „ 27

286,500 ...

14

189,000 ..

„ 29

147,000 ...

15

990,000 ..

„ 30- April 3

754,000 ...

19

14 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Eggs collected.

Date.

Larvre S('t free.

1 )ate.

619,000 ...

April

5 and 6

441,000 ...

„ 21

331,000 ...

yy

7

257,000 ...

„ 22

1,063,000 ...

y y

8 and 9

849,000 ...

„ 24

683,000 ...

,,

12 and 13

520,000 ...

„ 26

194,000 ...

yy

14

142,000 ...

„ 27

957,000 ...

yy

15-20

667,000 ...

May 3

9,825,500

7,124,500

“A few thousands of additional fertilised eggs were
collected on April 28tli and May lOtli ; but the resulting
larvae were retained In the hatchery for scientific observa-
tion and experiment.

“ The Curator regrets to say that, in spite of continued
efforts and experiments on new lines, the problem of
artificial lobster rearing remains practically unsolved.
The initial difficulty — that of obtaining berried female
lobsters with nearly ripe eggs — was greatly felt during
the past season, and the total number of larvae hatched did
not reach 1,500. A wooden tank measuring 6x0x4 feet,
with openings screened with wire gauze in the sides and
bottom, w^as fixed in the western spawning pond, and an
attempt was made to rear in it a number of lobster larvae.
This, in spite of abundant food material and liberal
aeration of the water, proved a failure, none of the
larvae surviving the third stage of development. Mr. W. J.
Ashburner, who made the tank, has further provided an
apparatus for keeping the water therein in constant
motion, and with this further experiments are to be made
next summer. There is evidence that berried lobsters will
retain their eggs if kept in the pond and provided wdth
suitable hiding places; and the Curator is now
accumulating a stock in the hope of ensuring a large
number of larvae next year.

MARINE RIOLOGTCAL STATION AT PORT ERIN.

15

“ In response to an invitation by the Isle of Man
Fisheries Board, representatives of the various Insular
education authorities met in the junior laboratory on
April 6th to hear an address from Professor Herdman on
“ Education,’’ especially in its relations to modern science
and modern requirements. The Deemster Callow
occupied the chair, the Clerk of the Rolls and other
members of the Council of Education were present, and
in the course of the lecture Professor Herdman showed
how an institution such as the Biological Station might
be utilised by the schools of the Island for purposes of
training in observation and for giving facilities to
teachers in connection with some aspects of higher
education.”

Mr. Dakin’s Report.

The following is a brief account of some of the
research carried out during my stay at Port Erin, which
lasted four months, from April 1st until the end of July.
My time was spent chiefly on three subjects, two of which
are more or less related, and work on these was com-
menced at the Zoological Station of Naples. During the
month of April, whilst Professor Herdman was at Port
Erin, I took charge of the hydrographical observations
made from his yacht, simultaneously with the plankton
catches. There is now a very complete set of hydro-
graphic apparatus at Port Erin, and I was able to fit up
a small chemical laboratory with the necessary apparatus
for the analysis of sea- water, so far as chlorine and oxygen
are concerned. A very complete series of observations
was made, which will be published in connection with
Professor Herdman’s Plankton Studies. After the Easter
vacation, quantitative tow-nettings were taken regularly
twice a week at a locality out at sea, two to three miles

16 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

west of the BrealvAvater, and these were continued until
the first week in July. They demonstrated, probably for
the first time in the Irish Sea, the length of the period of
the vernal diatom maximum, which this year extended
to May 24th.

“ My other work dealt with the minute histology of
the eye of Pecten, and a study of the visceral ganglion
and the innervation of the osphradium in the Lamelli-
branchiata. The former research is being published in
the Quarterly Journal of Microscopical Science, and a
preliminary communication on the latter will be given
here. Representatives of twelve genera belonging to nine
sub-orders have been examined, and the course of the
osphradial nerves has been traced by the method of
serial sections. In several recent text-books, statements
have been made, based apparently on a short paper of
Pelseneer’s, that the osphradium is innervated by the
cerebral ganglion. Thus in the volume on the Mollusca
in Ray Lankester’s ' Treatise on Zoology,’ we have ^ The
osphradial ganglion receives nerve fibre not from the
visceral ganglion, but from the cerebral ganglion by way
of the visceral commissure.’ A similar statement occurs
in Lang’s ‘ Comparative Anatomy.’ I find that in all the
species examined, the osphradial nerve fibres arise from
the branchial nerve, which takes its origin in the visceral
ganglion, except in the case of Pecten maximus, where, in
addition to this, two distinct nerves can be traced directly
from the ganglion. No nerve fibres leave the cerebrovisceral
connectives for the direct innervation of the osphradium.

“During the examination of some of these- lamelli-
branchs, the remarkable Nemertean M alacohdella was
discovered in the pallial cavity of Venus casina, and also
in Mya truncata from Piel. The usual host is Cyprina
islandica, but I am not aware of any previous records of

MARINE BIOLOGICAL STATION AT PORT ERIN.

17

tlie occuiTence of this Nemertean worm in the Port Erin
district, or of its occurrence in these two molluscs, though
Mr. Johnstone tells me he has found it in My a truncata
at Piel. It is probably not restricted to these three species.

'' An interesting ciliate Infusorian, Licnojphora
auei^)acJiii, which is also, I believe, a new record for the
district, turned up on the tentacles of Pecten maximus.

I should like to thank Professor Herdman, and
also Mr. Chadwick, for the space allotted to me in the
laboratory, which exceeded, I am afraid, very consider-
ably the normal bounds, and for all the trouble they have
taken to facilitate my work in various ways.”

Mr. Gravely’s Report.

‘‘ The stormy weather this summer interfered con-
siderably with work on pelagic larvae. For it was found
that healthy specimens disappeared from the plankton
during a storm, and did not return until almost all the
sand which was stirred up had settled down again— a
process which always took several days to complete. The
only larva which I have to record as new to the bay is
‘ 0 fhiojjluteus cornjpressus,’ of the ‘ Nordisches Plankton,’
a single specimen of which was taken on July 22nd. As
this presents a mode of development not hitherto recorded
in Ophiuroids, a description of it may be of some interest.
The hydrocoel is situated on the left of the alimentary
canal, and extends forwards slightly beyond the mouth,
which would be perfectly symmetrical if it were not
slightly drawn out into a point on the left side. The part
of the hydrocoel near the mouth, however, will not
eventually surround it, for it already bears at least two
pairs of developing tube-feet : and (from the presence and
position of similar papillse on other parts of the larva, and
of certain small plates that appear to be developed in

B

18 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

connection witli the hydrocoel') it is evident that this i^
already star-shaped; that it is situated entirely on the
left side of the pluteus and orientated as in Echinoplutei
at this stage; and that the larval mouth will not take
part in the formation of the permanent mouth. Moreover,
as in Echinus again, there appears to he a membrane
closing in an amniotic (‘avity, into which the tube-feet
project. The plates of the Ophiuroid to which the larva
gives rise have developed to such an extent that the
‘ terminal ’ plates of the arms project from the body in
the form of a star, hut (like the hydrocoel) instead of
lying in the horizontal plane of the pluteus, as is usually
the case at such an advanced stage of development, they
lie in a plane at right angles to this — the plane in which
they always make their first appearance in Ophioplutei.
The plates of the aboral surface have reached a
corresponding stage in their development, and also lie
roughly in the plane of their original formation. These
‘ terminal ’ and aboral plates do seem to have moved very
slightly towards the position assumed In^ those of other
Ophioplutei, but this movement, as shown by the position
of the middle of the central (aboral) plate, only amounts
to a rotation through about 12° instead of 90°. It is
unlikely, in view of the (condition of the hydrocoel, that
any further rotation will occur; but that some migration
of plates will take ])lace is shown by the position of the
' terminal ’ plate corresponding to the forwardly directed
arm of the hydrocoel. This plate, as noted above, is still
in its original position (i.e., near the stomach of the
pluteus), whereas this arm of the hydrocoel extends
beyond the mouth. Thus the directness of development
found in Echinus, where the plates and soft parts arise
together in their final relative positions, has not been fully
acquired by this Ophiuroid.

MARINE BIOLOGICAL STATION AT PORT ERIN.

19

“ From this account it will be seen that the mode of
development of 0 ‘phio'pluteiis co?npressus, whilst retaining
traces of that usually found in Ophiuroids, is as a whole
much more like that of Echinoids.

“ A few specimens of the epauletted Ophiopluteus
noted in my last year’s report were again obtained. They
are probably identical with Mortensen’s Ophiopluteus
henseni, a species described from a single specimen from
Bermuda in the report of the German plankton expedi-
tion. The absence of the skeleton in Mortensen’s
specimen, however, must make any identification a little
uncertain.

The following Polychaets, all from under stones
and Laminarian roots at Poyllvash^ are, I believe, new to
the L.M.B.C. Sphaefodorum sp., N emato nereis sp.,

Htaurocephalus sp., Scoloplos (Theodisca) mamillata
(Clap.) — also found in Port Erin Bay below the Biological
Station, Polydora caeca ((Erst.), and Dodecaceria {? ? con-
< ha nun, (Erst.).

As all these worms were obtained in two short
visits, a full investigation of the locality would probably
yield many more new forms.

“ Amongst the Laminarian roots a small specimen of
the locally rare Phascolosonia vulgar e was found, and
a smaller Gephyrean was fairly abundant. The specimens
of the latter are maggot-like creatures, 5-8 mm. in
length, with an introvert of about 4-6 mm. The lopho-
phore is represented, as in the genus Petalostoma, only by
a pair of lobes — which, however, vary a great deal in
distinctness, and often appear to be entirely absent.
Moreover, the Poyllvash species differs from the type
(P. imnutum, Ref.) in having only two instead of four
retractors.

As no investigations of the worm parasites of the

•^0 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIJ^TY.

district a])])enr to liavc l)eeii made as yei, I sliould like io ^
record here the great ahinidaiice of the curious Gregariiie !
Ancora {Anchorma, Miug.) sa(/ittata in the gut of the ;

common CajAtella of Port Krin sands, and of the ( ?) cilia te .

Ano'jjl oj)h rya in the gut of Cirratuluf^A I

Dr. E oaf’s Physiological Work. i

I

Dr. TT. E. Eoaf continued his investigations of last I
year'*' on the digestive processes in marine invertebrates. '
The results so far are partly in the form of observations
on the nature of the food and the manner of feeding of
several species, but more especially of Echinus esculenfus, :
and partly experiments directed to determine the presence
of acid or alkali in the alimentary canal during digestion. !
This latter investigation was carried out by using food i
dyed with chemical indicators, so that on examination ;
after various periods of digestion the degree of the
reaction could be determined. These experiments also ‘

gave some information as to the reaction of the organs, j

other than digestive, as the indicators when absorbed j

were capable of colouring the tissues in general. j

A large white anemone [Actinoloha dianthus) was fed j

with pieces of fibrin soaked in methylene blue, with the j

result that the tentacles, and to a less extent the mouth- j

disc, became stained in a most striking manner. The blue |

tint is remarkably persistent, and remained unaltered for j

seven months, while the anemone was under observation \

in the tanks. Mr. Chadwick states that the colour has j

recently become re-distributed, and is now confined to a
series of bands running circularly around the body-wall,
and especially at the upper end close to the bases of the
tentacles.

* Since published in the Bio-ChemicalJournal, Vol. iii,, 1908, pp. 462-472.

MARINE BIOLOGICAL STATION AT PORT ERIN.

21

Whilst collecting large white anemones for this and
similar work, Dr. Roaf found a speciiften (see fig. 4)
which was nearly divided into two distinct anemones. The
mouth-discs and circles of tentacles are absolutely
separate, but the two bodies join about two-thirds of the
way up from the base. This is probably a case of
partial fission, such as is known to occur sometimes in this
and other anemones. G. H. Parker has described it in the

Fig. 4.— Specimen of AcUnoloba diantkus showing fission.

American Metridium marginatum^ and Dr. J. A. Clubb
found the same in a Metridium (Actinoloba) from the
Mersey, which completed its longitudinal fission in the
tanks under his observation. Dr. Roaf found that when
one mouth was fed with neutral-red stained food, the neigh-
bouring tentacles became pink and remained coloured for
four weeks, while those around the other mouth remained
white. When one disc was stimulated the tentacles of
that part contracted, and those of the other only followed
more slowly after a slight interval, probably as a result
of a secondary stimulation caused by the contracted state

22 TRANSACTIONS LIVERPOOL JilOLOGiCAL S0CIP:TV.

of the neighbouring body exercivsing a pull upon the
tissues. It is therefore inferred that in this Siamese-
twin ” arrangement there is no communication between
the digestive cavities and no direct nervous connection.

Dr. Itoaf made a number of interesting observations
on the manner in which Kcliinui<, tlie Sea-urchin, catches
its food and passes it around the body by means of its
petdicellariie, spines and tube feet, and on the movements
of the teeth wlien tlie desirable particle is approaching the
mouth. All of these investigations will be published in
fuller detail in a paper to appear shortly.

Dr, Francis Ward's Piiotomtcrograriis.

(See Plates II and III, pp. 84 and 35).

At the invitation of Professor Herdinaji, I show
(Plates II and III) a few photographs of the early life-
history of the plaice taken in the Fish Hatchery at INnl
Erin in May, 1909, and will describe the methods I em-
ployed in making these records of the living specimens.
No. 1 shows the Plaice Larva almost hatched, x 25.

‘‘ I noticed that during hatching the tail is. frequently
used as a fixed point; and then by spasmodic contractions
of the back muscles the head and shoulders are made to
impinge on the edge of the originally small rent in the
egg membrane, until the opening is torn large enough to
permit the larva to escape.

No. 2 shows the Plaice Larva hatching tail first, x 25.

“ In photographing various larvie hatcbing, I liave
observed that certain fish, e.g., the Perch (^Ferca
fluviatilis), which have a very small yolk sac, hatch tail
first, then the body, and lastly the head, through a small
hole ; but with Plaice larvae, as with Salmonoid Alevins,
hatching is delayed at the stage shown until the head also
breaks (hrongh.

MARINE BIOLOGICAL STATION AT PORT ERIN.

23

No. 3. Plaice Larva Latched 3 minutes, 6‘5 mm. in
length, X 15.

“ In Xo. 3 the light was moved slightly to one side, so
that the illumination was partly by transmitted and
partly by reflected light, and the light being no longer
directed into the lens, a dark background was obtained.
This method is very useful in photographing delicate
structures.

“ Xos. 4 to 9 (PL III) show the changes by which the
bi-laterally symmetrical larva becomes an asymmetrical
flat fish. All are enlarged about 7 times.

No. 4. Larva just hatched, length 6‘5 mni.

No. 5. Larva hatched 7 days, length 7*5 mm.

No. 6. Larva of length 9’5 mm.

No. 7. Larva of length 10 mm.

‘‘ This specimen shows a greater relative growth dorso-
veiitrally than longitudinally, a sign of commencing
metamorphosis which is supposed to occur about the 30th
day after hatching.

No. 8. Larva of length 11 '5 mm.

“ This shows the rotation of the cranium through its
longitudinal axis, and the consequent carrying over of the
left eye.

No. 9. Larva of length 13 mm.

‘‘ This shows the metamorphosis progressing, and the
next stage examined showed it completed.

The first five photographs were from ova or larva) in
the hatching boxes ; the last four specimens were obtained
from the spawning ponds at the Biological Station. All
the specimens were photographed while alive, except
X6. 9. In this case I waited until the heart stopped
beating, in order to show that structure satisfactorily.

“ As to the apparatus used : — A deal board, four feet
long and six inches wide, carried on one side two rails,

24 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

four indies apart, running the whole length. At one end
of the hoard was screwed a 5 x 4 Planex lleflex camera.
I removed the panel carrying the lens, and temporarily
fixed on a 10-inch wooden extension for the lower
magnifications, and a longer extension made with wire
and hrown })aper for the higher magnifications. These
extensions ran along tlie lails as the camera was racked
out. A 2-inch block of wood, also running on the rails.

3.

4.

Fig. 5. — Four stages in the early development of the Plaice before
hatching. From photomicrographs by Edwin Thompson.

carried a cell in which was the living larva in sea-water.
A second block of wood carried an 8- inch condenser. The
illumination was obtained from an acetylene bicycle
lamp.

“ The lens used for photographs 1, 2 and B was a Zeiss
micro-planar of B5 mm. focal length ; and for photographs
4 to 9 a Bi-inch Beck. The leases were stopped down

MARINE BIOLOGICAL STATION AT PORT ERIN.

25

from F 11 to F IG, and the exposures varied from 10 to
15 seconds.

For this kind of work the best lens is one of about
d-inch focal length, the magnification being obtained by
having the plate a considerable length from the lens ; by
this means the whole thickness of the object to be photo-
graphed can be brought into focus without having to use
a small stop and so sacrifice light.

“ These photographs were taken with the cell in a
vertical position, and the cell used was just the depth of
the object to be photographed, which object was kept in
position by the cover glass. This method entails
considerable trouble, and there is a danger that the
specimen may be compressed.

“ Since returning from Port Erin I have constructed a
more elaborate apparatus, so as to be able on my next
visit to photograph specimens with the cell in a horizontal
position, and so avoid all risk of compression.

‘‘I have to thank Mr. Chadwick, and his assistant,
5Jjl\ T. Cregeen, for the immense trouble they took in
procuring suitable specimens in the successive stages, and
Mr. AV. J. Dakin for many useful suggestions.”

In addition to the above described work by Dr. F.
Ward, our Hon. Treas., Mr. Edwin Thompson, has devoted
much attention during the year to making Photomicro-
graphs of living Plankton. Fig. 5 shows four of his series
illustrating the embryonic development of the plaice.
These all represent earlier stages than those figured by
Dr, Ward (PI. II.) , which commenced with the hatching
of the larvae. Mr. Thompson has also prepared a number
of photomicrograjihs of typical samples of different kinds
of plankton, and a few of these are shown in PI. I,, p. 33.

26 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

“OUR FOOD FROM TILE SEA.’’

It is plain, from questions that liave been asked from
time to time l)y readers of these Annual Re])orts and by
visitors to the Biological Station, that some of our
supporteis, both in Livei‘})ool and the Isle of Man, would
be glad of further information as to the nature of
“ Plankton,” and as to the method and object of that
Plankton investigation to which so much attention has
been devoted during recent years. I shall tlierefore quot('
here, with a few alterations and additions, some
paragraphs from an address on “ Our Food from the
Waters,” given before the British Association, at
Winnipeg, this autumn — the argument being that the
marketable fish which man obtains from the sea and from
fresh-waters are ultimately dependent for existence upon
the minute plants and animals found in varying quantity
in all Avaters, and knoAvn as “ Plankton” ; and that in
collecting, examining and attempting to estimate the
quantities of such organisms, under different conditions,
and to account for the marked variations in these
quantities, the Biologist is dealing with important
economic questions, and at the same time is brought face
to face with some of the greatest Avorld problems still
unsolved by science.

It is possible to collect samples of the surface
Plankton of the sea in any required quantity per day or
hour from an ocean liner going at full speed, and such
gatherings have now been made from traverses across
several of the great oceans. The method is simple, effec-
tive, and inexpensive ; and the gatherings, if taken
continuously, give a series of samples amounting to a
section through the surface layer of the sea, a certain
volume of water being pumped in continuously through

MARINE JilOLOGlCAL STATION AT PORT ERIN.

27

the bottom of the ship, and strained through the fine silk
nets, the mesh of which may be the three-hundredth of an
inch across, before passing out into the sea again. In
examining with a microscope such a series of gatherings
across an ocean, two facts are broiiglit prominently before
the mind :

Pig. 6. — The Hensen Quantitiitive Net.

(1) The constant j)resence of a certain amount of
minute living things;

(2) The very great variation in the quantity and in
the nature of these organisms.

28 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Such Plankton gatherings taken continuously from
a,n ocean liner give, however, information only in regard
to the surface fauna and flora of the sea — including many
organisms of fundamental importam^e to man as the
immediate or the ultimate food of hshes and whales and
other useful animals.

It was therefore a great advance in Planktology when
Professor Victor llensen (1(S87) introduced his vertical,
(luantitative nets (fig. (i) which could he lowered down and
drawn up through any required zones of the water. The
highly original ideas and the ingenious methods of
llensen and his colleagues of the Kiel School of
Planktology — whether all the conclusions which have
been drawn from their results be accepted or not — have
at the least inaugurated a new epoch in such oceano-
graphic work ; and have inspired a large number of
disciples, critics and workers in most civilised countries,
with the result that the distribution of minute organisms
in the oceans and the fresh waters of the globe is now
much more fully known than was the case twenty, or even
ten, years ago. But perhaps the dominant feeling on the
part of those engaged in this work is that, notwithstanding
all this activity in research and the mass of published
literature to which it has given rise, much still remains to
be done, and that the Planktologist is still face to face
Avith some of the most important unsolved problems of
Biology.

The fundamental ideas of llensen were that the
Plankton, or assemblage of more or less minute drifting
organisms (both animals and plants) in the sea, is
uniformly distributed over an area where the physical
conditions are approximately the same, and that by taking
a comparatively small number of samples it Avould be
possible to calculate the quantity of Plankton contained

MARINE BIOLOGICAL STATION AT PORT ERIN.

29

at tlie time of observation in a given sea area, and to
trace the changes of this Plankton botli in space and time.
This was a sufficiently grand conception, and it has been
of great service to science by stimulating many workers
to further research. In order to obtain answers to the
problems before him, Hensen devised nets of the finest
silk of about 6,000 meshes in the square centimetre, to
be hauled up from the bottom to the surface, and having
their constants determined so that it was known what
volume of water passed through the net under certain
conditions. (See figure of the silk on PI. IV., p. 36).

Now, if this constancy of distribution postulated by
ITensen could be relied upon over considerable areas of
the sea, far-reaching conclusions, having important
bearings upon fisheries questions, might be arrived at;
and such have, in fact, been put forward by the Kiel
Planktologists and their followers, and have been quoted
on many occasions.

Such generalisations are most attractive, and if it
can be established that they are based upon sufficiently
reliable data, their practical utility to man in connection
with sea-fishery legislation will be very great. But the
comparatively small number of the samples, and the
observed irregularity in the distribution of the Plankton,
such as the examples given for the Irish Sea in the last
two of these Annual Eeports, and over still wider areas
such as the North Sea, leave the impression that further
observations are required before such conclusions can be
accepted as established.

Of the criticisms that have appeared in Germany, in
the United States and elsewhere, the two most funda-
mental are : (I) that the samples are inadequate ; and
(2) that there is no such constancy and regularity in
distribution as ITensen and some others have supposed.

80 TI^AXSACTTOXS TJ VKT? I’OOl, mOT.OGTCAL SOCIETY.

It has been shown by Kofoid, by Lohmann, and by others
fhnt there are imperfeetions in tho methods which were
not at first realised, and that under some circnmstances
anythin" from 50 to 08 per cent, of the more minute
organisms of the Plankton may escape capture by the
finest silk (|uantitative nets. O’he mesh of Ihe silk is

8. — The same quantitative plankf
ne+^^ coming up closed. b

ll

1 -Booth inch across, but many of the organisms are only ;
l-3000th inch in diameter, and so can readily escape.

Other methods have been devised to supplement the
llensen nets, such as the filtering of water pumped up
through hose-pipes let down to known depths, and also
the micios(*opic examination in the laboratory of the
centrifuged contents of comparatively small samples of

Fig. 7. —Closing Petersen-Hensen Net
“going down open. ,

MARINE BIOLOGICAL STATION AT PORT ERIN.

B1

water obtained by means of closing water-bottles from
various zones in the ocean. Rut even if deficiencies in
the nets be thus made good by supplementary methods,
and be allowed for in the calculations, there still remains
the second and more fundamental source of error, namely,
unequal distribution of the organisms in the water; and
in regard to this a large amount of evidence has now been
accumulated, since the time when Darwin, during the
voyage of the “ Beagle ” on March 1<S, 18B2, noticed off
the coast of South America vast tracts of water discoloured
by the minute floating Alga, T richoclesmium erythrceum,
which is said to have given its name to the Med Sea, and
which Captain Cook’s sailors in the previous century
called “ sea-sawdust.” Many other naturalists since have
seen the same phenomenon, caused both by this and by
other organisms. It must be of common occurrence, and
is widespread in the oceans, and it will be admitted that
a quantitative net hauled vertically through such a
Trichodesmium bank would give entirely different results
from a haul taken, it might be, only a mile or two away,
in water under, as far can be determined, the same
])hysical conditions, but free from Trichodesmium.

Nine nations bordering the North-West seas of
Europe, some seven or eight years ago, engaged in a joint
scheme of biological and hydrographical investigation,
mainly in the North Sea, with the declared object of
til rowing light upon fundamental facts bearing on the
economic problems of the fisheries. One important part
of their programme was to test the quantity, distribution,
and variation of the Plankton by means of periodic
observations undertaken four times in the year (February,
May, August and November) at certain fixed points in the
.sea. ^lany biologists considered that these periods were
too few and the chosen stations too far apart to give

82 TlfANSACT10^^S LTVERPOOL BIOLOGICAL SOCIETY.

i'(‘lial)lc results. It is possilile tliat (‘veu the ori^’inal
promoters ot tlie sclieme would now share that view, and
the opinion has recently been jiublished by the American
Planktologist, Professor C. A. Kofoid than whom no one
is better entitled, from his own detailed and exact work,
to express an authoritative verdict — that certain recent
observations “ can but reveal the futility of the Plankton
]irogramme of the International Commission for the
investigation of the sea. The quarterly examinations of
this programme will, doubtless, yield some facts of value,
but they are truly inadequate to give any reliable view of
the amount and course of Plankton production in the sea.”*

It is evident that before we can base far-reaching
generalisations upon our Plankton samples, a minute
study of the distribution of life in both marine and fresh
waters at very frequent intervals throughout the year
should be undertaken. Kofoid has made such a minute
study of the lakes and streams of Illinois, and C. D. Marsh
of those of Wisconsin; and similar intensive work is now
being carried out at several localities in Europe.

Too little attention has b(^en paid in the past to the
distribution of many animals in swarms, some parts of the
sea being crowded and neighbouring parts being destitute
of such forms, and this not merely round coasts and in the
narrow seas, but also in the open ocean. For example,
some species of Copepoda and other small Crustacea occur
notably in dense crowds (fig. II, PI. I), and are not uni-
versally distributed. This is true also of some of the
Diatoms, and also of larger organisms. Many
naturalists have remarked upon the banks of
Trichodesmium, of Medusa? and Siphonophora, of
Salpae, of Pteropods, of Peridinians and of other

* “Internationale Revue der Hydrobiologie und Hydrographie,”
Vol. I., p. 846, December, 1908.

Plate I.

33

Fig. 9. Peridinian Plankton, consisting
mainly of Ceratium tripos.

Fig. 10. Plankton, consisting almost
wholly of Noctiluca viiliaris.

Pig. 11. Copepod Plankton, consisting mainly Fig. 12. Diatom Plankton, consisting
of Acartia discaudata. One Temora is seen. mainly of Coscinodiscus and Biddulphia.

Plate III.

35

3()

Platk IV.

Fig. 18. Nauplius stage of Balanus.

Fig. 19. Cypris stage of Balanus.

Fig. 20. Mesh of No. 20 silk
when new. x 23

Fig. 21. Mesh of same silk after use
in Nansen net for some months, x 23

. MARINE BIOLOGICAL STATION AT PORT ERIN.

37

common constituents of the Plankton. It is possible, how-
ever, that in some parts of the ocean, far from land, the
Plankton may be distributed with the uniformity supposed
by Hensen. It is important to recognise that at least three
classes of locality exist in the sea in relation to distribution
of Plankton : — ‘

(1) There are estuaries and coastal waters where
there are usually strong tidal and other local currents,
with rapid changes of conditions, and w^here the Plankton
is largely influenced by its proximity to land.

(2) There are considerable sea areas, such as the
centre of the North Sea and the centre of the Irish Sea,
where the Plankton is removed from coastal conditions,
but is influenced by various factors which cause great
irregularity in its distribution. These are the localities
of the greatest economic importance to man, and to which
attention should especially be directed.

(3) There are large oceanic areas in which there may
be uniformity of conditions, but it ought to be recognised
that such regions are not those in which the Plankton is
of most importance to men. The great fisheries of the
world, such as those of the North Sea, the cod fishery in
Norway, and those on the Newfoundland Banks, are not
in mid-ocean, but are in areas around the continents,
where the Plankton is irregular in its distribution.

As an example of a locality of the second type,
showing seasonal, horizontal and vertical differences in
the distribution of the Plankton, we may take the centre
of the Irish Sea, off the south end of the Isle of Man.
Here, as in other localities which have been investigated,
the Phyto-Plankton is found to increase greatly about the
time of the vernal equinox, so as to cause a maximum,
largely composed of Diatoms, at a period ranging from
the end of March to some time in May. During this period
c

38 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY..

the eggs of most of the edible fishes are hatched as lai'va3.
Figure 13 shows the cuiwe formed by the catches of the
total plankton in Port Erin Bay during 1908.

This Diatom maximum is followed by an increase in
the Copepoda (minute Crustacea), which lasts for a con-
siderable time during the early summer; and as the fisli
larvm and the Copepoda increase there is a rapid falling
ofi; in Diatoms. Less marked maxima of both Diatoms and
Copepoda may occur again about the time of the autumnal

Copepoda (fig. 11) — are the most important economic con- |
stituents in the Plankton. A few examples showing their |
importance to man may be given: — Man eats the oyster t
and the American clam, and these shell-fish feed upon Dia- |
toms. Man feeds upon the cod, which in its turn may feed ' 1
on the whiting, and that on the sprat, and the sprat on
Copepoda, while the Copepoda feed upon Peridinians and \
Diatoms ; or the cod may feed upon crabs, which in turn 1
eat “ worms,” and these feed upon smaller forms which I
are nourished by the Diatoms. Or, again, man eats the V

MARINE BIOLOGICAL STATION AT PORT ERIN.

39

mackerel, wkicli may feed upon young herring, and these
upon Copepoda, and theCopepoda again upon Diatoms. All
such chains of food matters from the sea seem to bring one
through the Copepoda to the Diatoms, which may be
regarded as the ultimate “ producers ” of food in the ocean.
Thus the living food of man from the waters of the globe
may be said to be the Diatoms and other microscopic
organisms quite as much as the hshes.

Fig. 14. — Four samples of plankton taken with the same net, in the
same locality, between April 5th and 15th, 1907,
and ranging from 13 c.c. to 100 c.c.

Two years ago, at the Leicester meeting of the British
Association, I showed that if an intensive study of a small
area be made, hauls being taken not once a quarter or
once a month, but at the rate of ten or twelve a day,
abundant evidence will be obtained as to : (1) variations in
the distribution of the organisms, and (2) irregularities in
the action of the nets. Great care is necessary in order to

40 TKANSACTIONS LI VEUPOOL BIOLOGICAL SOCIETY-

ensure that hauls intended for comparison are really
comparable. Two years’ additional work since in the same
locality, off the south end of the Isle of Man, has only
confirmed these results, viz., that the Plankton is liable
to be very unequally distributed over the depths, the
localities, and the dates. One net may encounter a swarm
of organisms which a neighbouring net escapes, and a
sample taken on one day may be very different in quantity
from a sample taken under the same conditions next day.
If an observer were to take quarterly, or even monthly,
samples of the Plankton, he might obtain very different
results according to the date of his visit. For example, on
three successive weeks about the end of September he
might find evidence for as many different far-reaching
views as to the composition of the Plankton in that part
of the Irish Sea. Consequently, hauls taken many miles
apart and repeated only at intervals of months can scarcely
give any sure foundation for calculations as to the
population of wide sea areas.

These conclusions need not lead us to be discouraged
as to the ultimate success of scientific methods in solving
what may be called world-wide problems, but they suggest
that it would be wise to secure by detailed local work a
firm foundation upon which to build, and to ascertain
more accurately the representative value of our samples
before we base conclusions upon them.

I do not doubt that in limited, circumscribed areas of
water, in the case of organisms that reproduce with great
rapidity, the Plankton becomes more uniformly
distributed, and a comparatively small number of samples
may then be fairly representative of the whole. That is
probably more or less the case with fresh-water lakes;
and I have noticed it in Port Erin Bay in the case of
Diatoms. In spring, and again in autumn, when suitable

MARINE BIOLOGICAL STATION AT PORT ERIN.

41

weather occurs, as it did two years ago at the end of
September, the Diatoms may increase enormously, and in
such circumstances they seem to be very evenly spread
over all parts and to pervade the water to some depth ;
but that is emphatically not the case with the Copepoda
and other constituents of the Plankton, and it was not the
case even with the Diatoms during the succeeding year.

I have published in a former report an observation

Fig. 15. — Series of plankton gatherings showing “ swarms” of certain
organisms (Haeckel’s “ Monotones Plankton”).

The jars contain mainly Sagitta, Medusae, Zoea, Calanus, and smaller
Copepoda, going from left to right.

that showed very definite limitation of a large shoal of
crab Zoeas, so that none were present in one net while in
another adjacent haul they multiplied several times the
bulk of the catch and introduced a new animal in
enormous numbers. Had two expeditions taken samples
that evening at what might well be considered as the same
station, but a few hundred yards apart, they would have

42 'rUANSACTIONS LTVERPOOr. mOLOGlCAL SOCIETY.

arrived at very different conclusions as to the constitution
of the Plankton in that part of the ocean.

It is possible to obtain a great deal of interesting
information in regard to the “ hylokinesis ” (or changes of
matter) of the sea without attempting a numerical
accuracy which is not yet attainable. The details of
measurement of catches and of computations of organisms
become useless, and the exact figures are non-significant,
if the hauls from which they are derived are not really
comparable with one another and the samples obtained are
not adequately representative of nature. If the stations
are so far apart and the dates are so distant that the
samples represent little more than themselves, if the
observations are liable to be affected by any incidental
factor which does not apply to the entire area, then the
results may be so erroneous as to be useless, or worse than
useless, since they may lead to deceptive conclusions. It
is obvious that we must make an intensive study of small
areas before we draw conclusions in regard to relatively
large regions such as the N"orth Sea or the Atlantic Ocean.

That, however, is not an argument against the
legitimate use of quantitative methods, with limitations,
and for certain purposes. It is necessary to know more
than the fact that a certain species is present at a given
locality at a certain time. We must endeavour to get
some measure of its abundance, and that can only be done
satisfactorily by counting individuals ; at the same time
recognising the imperfections of the methods and the
approximate nature of the result, so that the numerical
estimate will be regarded as relative rather than absolute.
Our apparatus is not perfect enough, nor is the distribu-
tion of the organisms sufficiently uniform to enable us to
calculate how many individuals of a Diatom, of a
Copepod, or of a fish are present in the Irish Sea on a

MARINE BIOLOGICAL STATION AT PORT ERIN.

48

Fig. 1G. — Plankton nets drying after an expedition on S.Y. “ Ladybird ”
at Port Erin. (Photo by Edwin Thompson).

the changes, both diurnal and seasonal, and the deter-
mining factors of such changes, we must endeavour to
make quantitative catches as accurately and as frequently
as possible, so that our samples may be as nearly represen-
tative and as nearly comparable one with another as the
difficult conditions will admit. These catches should be
made with standard nets, should be preserved and
measured according to a uniform system, and may then be
compared in bulk; but, in addition, the more important

particular occasion ; but we may aim at being able to
make, with a reasonable approximation to the truth, such
statements as : There are about ten times as many Diatoms
in a special part of the Irish Sea now as there were last
week, and in round numbers twice as many as at the
corresponding period of last year.

'With the object of formulating such views as to the
nature of the Plankton at any particular time, and as to

44 TRANSACTIONS LIVERPOOL JOOLOGICAL SOCIETY.

organisms should be counted approximately, and the
results, in round numbers, may be used in comparing
catches or in tracing changes; but such figures should not
be made the basis of calculations as to the total numbers
of such organisms in the oceans. In brief, the numerical
results of quantitative work should be regarded as giving
relative but not absolute information.

Fig. 17. — Diagram showing the influence of the factors C, B, D,
upon the life-history A.

The factors causing the seasonal and other variations
in the Plankton already pointed out may be grouped under
three heads, as follows : —

(1) The sequence of the stages in the normal life
history of the different organisms.

(2) Irregularities introduced by the interactions of
the different organisms.

(3) More or less periodic abnormalities in either
time or abundance caused b}^ the physical changes in the
sea, which may be grouped together as “ weather.”

MARINE BIOLOGICAL STATION AT TORT ERIN.

45

These are all obvious factors in the problem, and the
constitution of the Plankton from time to time throughout
the year must be due to their interaction. The difficulty
is to disengage them from one another so as to determine
the action of each separately (See fig. IT which illustrates
the effect of the above factors).

Figure 18, on Plate TV, shows the Nauplius stage of
the common rock barnacle (Balanus) . The adult is present in
abundance on the rocks at Port Erin, and the Nauplii are
sometimes found in enormous swarms in spring. Figure
19 shows the succeeding or ‘‘ Cypris ” stage, found in our
tow-nets a little later and in much smaller quantities than
the Nauplius — the reduced numbers in the later stage of
the life-history being evidence of the action of enemies
and other factors of the environment.

Amongst the physical conditions coming under the
third heading, the temperature of the sea is usually given
a very prominent place. I shall allude here to one aspect
only of this matter.

It is often said that tropical and sub-tropical seas are
relatively poor in Plankton, while the colder Polar regions
are rich. In fishing Plankton continuously across the
Atlantic it is easy from the collections alone to tell when
the ship passes from the warmer Gulf Stream area into
the colder Labrador current. This is the reverse of what
we find on land, where luxuriant vegetation and abundance
of animal life are characteristic of the tropics in contrast
to the bare and comparatively lifeless condition of the
Arctic regions. Brandt has made the ingenious suggestion
that the explanation of this phenomenon is that the higher
temperature in tropical seas favours the action of
denitrifying bacteria, which therefore flourish to such an
extent in tropical waters as seriously to diminish the

4(i T1?ANSACTT0NS LIVERTOOI. RTOr.OGICAL SOCIETY.

supply of nitrogen food and so Hrait the production of
Plankton. Loeh,^ on the other hand, has recently revived
the view of Murray, that the low temperature in Arctic
waters so reduces the rate of all metabolic processes, and
increases the length of life, that we have in the more
abundant Plankton of the colder waters several genera-
tions living on side by side, whereas in the tropics with
more rapid metabolism they would have died and
disappeared. The temperature of the sea-water, however,
appears to have little or no effect in determining the great
vernal maximum of Phyto-Plankton.

Considering the facts of photosynthesis, there is much
to be said in favour of the view that the development, and
possibly also the larger movements, of the Plankton are
influenced by the amount of vSunlight, quite apart from any
temperature effect.

Bullent showed the correlation in 1903-07 between the
mackerel catches in May and the amount of Copepod
Plankton in the same sea. The food of these Copepoda has
been shown by Dakin to be largely Phyto-Plankton ; and
Allen has latelyj correlated the average mackerel catch
per boat in May with the hours of sunshine in the previous
quarter of the year, thus establishing the following con-
nection between the food of man and the weather : ---
Mackerel — Copepoda — Diatoms — Sunshine. One more

example of the influence of light may be given. Kofoid
has shown that the Plankton of the Illinois Eiver has
certain twenty-nine-day pulses, which are apparently
related to the lunar phases, the Plankton maxima lagging
about six days behind the times of full moon. The light
from the sun is said to be 618,000 times as bright as that

* Darwin and Modern Science (Cambridge, 1909), p. 247.
t M.B.A. Journ., viii. 269. \ M.B.A. Journ., vii. 394.

MARINE BIOLOGICAL STATION AT PORT ERIN.

47

from file full moon ; but the amount of solar energy
derived from the moon is sufficient, we are told, appre-
ciably to affect photosyiithesis in the Phyto-Plankton.
The effectiveness of the moon in this photosynthesis to
that of the sun is said to be as two to nine, and, if that is
so, Kofoid is probably justified in his contention that at
the time of full moon the additional light available has a
marked effect upon the development of the Phyto-
Plankton.

As on land, so in the sea, all animals ultimately
depend upon plants for their food. The plants are the
producers and the animals the consumers in nature, and
the pastures of the sea, as Sir John Murray pointed out
long ago, are no less real and no less necessary than those
of the land. Most of the fish which man uses as food spawn
in the sea at such a time that the young fry are hatched
when the spring Diatoms abound, and the Phyto-Plankton
is followed in summer by the Zoo-Plankton (such as
Copepoda), upon which the rather larger but still
immature food fishes subsist. Consequently the cause of
the great vernal maximum of Diatoms is one of the most
practical of world problems, and many investigators have
dealt with it in recent years. Murray first suggested that
the meadows of the sea, like the meadows of the land,
start to grow in spring simply as a result of the longer days
and the notable increase in sunlight. Brandt has put
forward the view that the quantity of Phyto-Plankton in
a given layer of surface water is in direct relation to the
quantity of nutritive matters dissolved in that layer. Thus
the actual quantity present of the substance— carbon,
nitrogen, silica, or whatever it may be — that is first used
up determines the quantity of the Phyto-Plankton.
Nathansohn in a recent paper^ contends that what Brandt
* “ Monaco Bulletin,” No. 140.

48 TRANSACTIONS LIVERPOOL BIOI-OGICAL SOCIETY.

supposes never really happens; that the Phyto-Plankton
never exhausts any food constituent, and that it develops
just such a rate of reproduction as will compensate for the
destruction to which it is subjected. This destruction he
holds is due to two causes : currents carrying the Diatoms
to unfavourable zones or localities, and the animals of the
Plankton which feed on them. The quantity of Phyto-
Plankton present in a sea will then depend upon the
balancing of the two antagonistic processes — the repro-
duction of the Diatoms and their destruction. We require
further knowledge in regard to their rate of reproduction
and the amount of the destruction ; but it has been
calculated that one of these minute forms, less than the
head of a pin, dividing into two at its normal rate of five
times in the day, would at the end of a month form a mass
of living matter a million times as big as the sun. The
destruction that keeps such a rate of reproduction in check
must be equally astonishing. It is claimed that the
“ Valdivia ’’ results, and observations made since, show
that the most abundant Plankton is where the surface
water is mixed with deeper layers by rising currents.
Nathansohn, while finding that the hour of the day has no
effect on his results, considers that the development of the
Phyto-Plankton corresponds closely with evidence of
vertical circulation. Like some other workers, he
emphasises the necessity of continuous intensive work in
one locality. The “ Challenger ” and other great exploring
expeditions forty years ago opened up problems of
oceanography, but such work from vessels passing
rapidly from place to place could not solve our present
problems — the future lies with the naturalists at biological
stations working continuously in the same locality the year
round. As an example of the complexity of such problems,
there seem to be two kinds of Diatom maxima found by

MARINE BIOLOGICAL STATION AT PORT ERIN. 49

Nathansohn in the Mediterranean, one of Chaetoceros
due to the afflux of water from the coast, and one of
Rhizosolenia calcar-avis, due to a vertical circulation
bringing up deeper layers of water.

The same principles and series of facts could be
illustrated from the inland waters. Lakes periodically
show Plankton maxima, which must be of vast importance
in nourishing animals, and eventually the fishes used by
man. Geologists have shown that Manitoba was in post-
glacial times occupied by the vast lake Agassiz, with an
estimated area of 110,000 square miles; and while the
sediments of the extinct lake form now the celebrated
wheat fields, supplying food to the nations, the shrunken
remains of the water still yield, it is said, the greatest
fresh-water fisheries in the world. It is to be hoped that
nothing will be done further to reduce this valuable
source of food. It is said that the Illinois fisheries yield
at the rate of a pound a day throughout the year of cheap
and desirable food to about 80,000 people — equivalent to
one meal of fish a day for a quarter of a million people.
The .Canadian whitefish alone has yielded, I see, in
recent years over 5,000,000 lbs. in a year, and all
scientific men who have considered fishery questions will
note ■with approval that all the fishing operations are now
carried on under the regulations of the Dominion
Government, and that fish hatcheries have been established
on several of the great lakes which will, along with the
necessary restrictions, form, it may be hoped, an effective
safeguard against depletion. Much still remains to be
done, however, in the way of detailed investigation and
scientific exploitation. It has been shown in European
seas that the mass of living food matters produced from the
uncultivated water may equal that yielded by cultivated
land. AVhen aquiculture is as scientific as agriculture the

50 TltA^^SACTlONS LIVEIU’OOL J31OL0G1CAJ. SOCIETY.

regulated and cultivated waters of North America, both
inland and marine, may prove to be more productive even
than the great wheat lands of Manitoba.

Inland waters may be put to many uses; sometimes
they are utilised as sewage outlets for great cities,
sometimes they are converted into commercial highways,
or they may become restricted because of the reclamation
of fertile bottom lands. All these may be good and
necessary developments, or any one of them may be
obviously best under the circumstances, but due regard
should always be paid to the importance and promise of
natural w'aters as a perpetual source of cheap and health-
ful food to the people of the country.

JAA/. FEB. MAR. APR Af.W. JUNE. JULY AUG SEPT. OCT NOV. DEC

The above curves show the result of the temperature observations
taken at the Biological Station during 1908, the last complete year.
They show very clearly how the temperature of the sea (dotted) lags
behind that of the air (whole lines), being higher in winter and lower
in the height of summer.

MARlI-fE BIOLOGICAL STATION AT PORT EPIN.

51

L.M.B.C. Memoirs.

During 1909 no less than three Memoirs have been
issued: — No. XVII, Pecten (the Scallop), by Mr. W. J.
Dakin, M.Sc. ; No. XVIII, Eledone (the local
“Octopus’'), by Miss A. Isgrove, M.Sc.; and No. XIX,
on Polychaet Larv.e (the young stages of the Higher
AVorms) at Port Erin, by Mr. E. H. Gravely, M.Sc.
Doris, the sea-lemon, by Sir Charles Eliot, and other
Memoirs are also far advanced; and we hope to have a
Memoir on our Irish Sea species of Ceratium and other
Dinoflagellata from Prof. C. A. Kofoid, who did some
Avork on our local material during his visit to our labora-
tory in 1908. This unusual amount of excellent material,
which the Committee is happy to be able to issue to the
scientific Avorld, is, however, embarrassing from the point
of view of expense. Lithographic plates, such as these
Memoirs require, seem to become more costly, and Avith
the groAving elaboration of the subject more detailed
illustration is necessary. The Committee are therefore
always very grateful for special donations and grants
AA’hich have in the past enabled the Treasurer to meet the
expenses of plates for several of the above-mentioned
Memoirs. Further donations to provide for the illustra-
tions of those still unpublished will be very welcome.

The following shows a list of the Memoirs already
published or arranged for : —

I. Ascidia, W. a. Herdman, 60 pp., 5 Pis.

II. Cardium, J. Johnstone, 92 pp., 7 Pis.

III. Echinus, H. C. Chadwick, 36 pp., 5 Pis.

lY. ComuM, P. J. H. Gibson and H. Auld, 3 Pis.

Y. Alcyonium, vS. j. Hickson, 30 pp., 3 Pis.

Yl. Lepeophtiieirus and Lern.ea, a. Scott, 5 Pis.

A^II. Lineus, P. C. Punnett, 40 pp., 4 Pis.

52

TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

YIII. Plaice, F. J. Cole and J. Johnstone, 11 Pis.
IX. Chondrus, 0. V. Darbishire, 50 pp., 7 Pis.

X. Patella, J. R. A. Davis and II. J. Fleure, 4 Pis.
XI. Arenicola, j. H. Ashworth, 126 pp., 8 Pis.

XII. Gammarus, M. Cussans, 55 pp., 4 Pis.

XIII. Anurida, a. D. Imms, 107 pp., 8 Pis.

XIV. Ligia, C. G. Hewitt, 45 pp., 4 Pis.

XV. Antedon, it. C. Chadwick, 55 pp., 7 Pis.

XVI. Cancer, -J. Pearson, 217 pp., 13 Pis.

XVII. Pecten, W. j. Dakin, 144 pp., 9 Pis.

XVIII. Eledone, a. Isgrove, 113 pp., 10 Pis.

XIX. Polychaet Larvj5, F. H. Gravely, 79 pp., 4 Pis.
Doris, Sir Charles Eliot.

CucuMARiA, E. Hindle.

Oyster, W. A. Herdman and J. T. Jenkins.
Ostracod (Cythere), Andrew Scott.

Buccinum, W. B. Randles.

Bugula, Laura R. Thornely.

Sagitta, E. j. W. Harvey.

ZosTERA, R. J. Harvey Gibson.

Himanthalia, F. j. Lewis.

Diatoms, F. E. Weiss.

Fucus, J. B. Farmer.

Botrylloides, W. a. Herdman.

Actinia, J. A. Clubb.

Hydroid, E. T. Browne.

Halichondria and Sycon, a. Dendy.
Sabellaria, a. T. Watson.

In addition to these, other Memoirs will be arranged
for, on suitable types, such as Fagurus, Fontohdella,
a Cestode and a Pycnogonid.

MARINE BIOLOGICAL STATION AT PORT ERIN.

53

We append to this Eeport: —

(A) The usual Statement as to the constitution of the
L.M.B.C., and the Laboratory Eegulations;

fB) The Hon. Treasurer’s Eeport, List of Subscribers, and
Balance Sheet.

Appendix A.

THE LIYEEPOOL MAEINE BIOLOGY
COMMITTEE (1909).

His Excellency the Eight Hon. Lord Eaglan, Lieut.-
Governor of the Isle of Man.

Et. Hon. Sir John Brunner, Bart., M.P.

Prof. E. J. Harvey Gibson, M.A., F.L.S., Liverpool.

Mr. W. J. Halls, Liverpool.

Prof. W. A. Herdman, H.Sc., F.E.S., F.L.S., Liverpool,
Chairman of the L.M.B.C., and Hon. Director of the
Biological Station.

Dr. W. E. Hoyle, M.A., Museum, Cardiff.

Mr. P. M. C. Kermode, Eamsey, Isle of Man.

The late Mr. Joseph Lomas, Liverpool.

Sir Charles Petrie, Liverpool.

Mr. E. Thompson, Liverpool, Hon. Treasurer.

Mr. a. 0. Walker, F.L.S., J.P., formerly of Chester.

Mr. Arnold T. Watson, F.L.S., Sheffield.

Curator of the Station — Mr. H. C. Chadwick, A.L.S.
Assistant — Mr. T. H. Cregeen.

D

54 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

CONSTITUTION OF THE L.M.B.C.

(Established March, 1885.)

• I. — The Object of the L.M.B.C. is to investigate the
Marine Fanna and Flora (and any related subjects such
as submarine geology and the physical condition of the
water) of Liverpool Bay and the neighbouring parts of
the Irish Sea and, if practicable, to establish and maintain
a Biological Station on some convenient part of the coast.

II. — The Committee shall consist of not more than 12
and not less than 10 members, of whom 3 shall form a
quorum; and a meeting shall be called at least once a
year for the purpose of arranging the Annual Report,
passing the Treasurer’s accounts, and transacting any other
necessary business.

III. — During the year the Affairs of the Committee
shall be conducted by an Hon. Director, who shall be
Chairman of the Committee, and an Hon. Treasurer,
both of whom shall be appointed at the Annual Meeting,
and shall be eligible for re-election.

IV. — Any Vacancies on the Committee, caused by
death or resignation, shall be filled by the election at
the Annual Meeting, of those who, by their work on the
Marine Biology of the district, or by their sympathy with
science, seem best fitted to help in advancing the work of
the Committee.

V. — The Expenses of the investigations, of the publi-
cation of results, and of the maintenance of the Biological
Station shall be defrayed by the Committee, who, for this
purpose, shall ask for subscriptions or donations from the
public, and for grants from scientific funds.

VI. — The Biological Station shall be used primarily
for the Exploring work of the Committee, and the
Specimens collected shall, so far as is necessary, be

MARIxXE BIOLOGICAL STATION AT PORT ERIN.

55

placed in the first instance at the disposal of the members
of the Committee and other specialists who are reporting
upon groups of organisms; work places in the Biological
Station may, however, be rented by the week, month, or
year to students and others, and duplicate specimens
which, in the opinion of the Committee, can be spared
may be sold to museums and laboratories.

LIVERPOOL MARINE BIOLOGICAL STATION

AT

PORT ERIN.

Laboratory Regulations.

I. — This Biological Station is under the control of the
Liverpool Marine Biological Committee, the executive of
which consists of the Hon. Director (Prof. Herdman,
F.R.S.) and the Hon. Treasurer (Mr. E. Thompson).

II. — In the absence of the Director, and of all other
members of the Committee, the Station is under the
temporary control of the Resident Curator (Mr. H. C.
Chadwick), who will keep the keys, and will decide, in the
event of any difficulty, which places are to be occupied by
workers, and how the tanks, boats, collecting apparatus,
&c., are to be employed.

III. — The Resident Curator will be ready at all
reasonable hours and within reasonable limits to give
assistance to workers at the Station, and to do his best
to supply them with material for their investigations.

IV. — Visitors will be admitted, on payment of a small
specified charge, at fixed hours, to see the Aquarium and

56 TllANSACTrONS LlVEIirOOL BIOLOGICAL SOCIETY.

Museum adjoining the Station. Occasional public lectures
are given in the Institution by members of the Committee.

V. — Those who are entitled to work in the Station,
when there is room, and after formal application to the
Director, are: — (1) Annual Subscribers of one guinea or
upwards to* the. funds (each guinea subscribed entitling to
the use of a work place for three weeks), and (2) others
who are not annual subscribers, but who pay the Treasurer
10s. per week for the accommodation and privileges.
Institutions, such as Universities and Museums, may
become subscribers in order that a work place may be at
the disposal of their students or staff for a certain period
annually ; a subscription of two guineas will secure a work
place for six weeks in the year, a subscription of five
guineas for four months, and a subscription of £10 for the
whole year.

VI. — Each worker is entitled to a work place opposite
a window in the Laboratory, and may make use of
the microscopes and other apparatus, and of the boats,
dredges, tow-nets, &c., so far as is compatible with
the claims of other workers, and with the routine work of
the Station.

VII. — Each worker will be allowed to use one pint of
methylated spirit per week free. Any further amount
required must be paid for. All dishes, jars, bottles, tubes,
and other glass may be used freely, but must not be
taken away from the Laboratory. TV^orkers desirous of
making, preserving, or taking away collections of marine
animals and plants, can make special arrangements
with the Director or Treasurer in regard to bottles and
preservatives. Although workers in the Station are free
tc make their own collections at Port Erin, it must be
clearly understood that (as in other Biological Stations)
no specimens must be taken for such purposes from the

MARINE BIOLOGICAL STATION AT PORT ERIN.

57

Laboratory stock, nor from the Aquarium tanks, nor from
the steam-boat dredging expeditions, as these specimens
are the property of the Committee. The specimens in
the Laborator3^ stock are preserved for sale, the animals
in the tanks are for the instruction of visitors to the
Aquarium, and as all the expenses of steam-boat dredging
expeditions are defrayed by the Committee, the specimens
obtained on these occasions must be retained by the
Committee (a) for the use ef the specialists working at
the Fauna of Liverpool Bay, (b) to replenish the tanks,
and (c) to add to the stock of duplicate animals for sale
from the Laboratory.

VIII. — Each worker at the Station is expected to lay
a paper on some of his results — or at least a short report
upon his work — before the Biological Society of Liverpool
during the current or the following session.

IX. — All subscriptions, payments, and other com-
munications relating to finance, should be sent to the
Hon. Treasurer, Applications for permission to work at
the Station, or for specimens, or any communications in
regard to the scientific w^ork should be made to Professor
Herdman, F.B.S., University, Liverpool.

Young Crabs (Zoea and Megalopa stages)— enlarged.

58 TRANSACTIONS LIVERPOOL 3J10L0G1CAL S0CIP:TY.

Appendix B.

HON. TREASUKEH’S STATEMENT.

As usual the financial statement for the year is shown
in the few following pages.

Three new L.M.B.C. Memoirs have been published
during the year, naniel}^ Pecten (the common scallop),
Eledone (an octoped cuttle fish) and Polychaet Larvse.
The two former are illustrated with finely lithographed
plates, and the cost of producing them is necessarily great.
Nineteen Memoirs have already been issued and there are
more in course of preparation. Doris by Sir Charles Eliot
is already far advanced, and it is hoped that Zostera,
Sagitta, Buccinum and the Oyster will follow soon.

ITnless more funds are forthcoming the publication
of these Memoirs will have to be delayed, and the Treasurer
hopes that further donations will be received to meet their
cost. The Aquarium at Port Erin continues to prove a
source of great interest to visitors to the Isle of Man, but
owing to the bad season it is to be regretted that the present
receipts do not quite equal those of last year.

The expenses of the Biological Station annually grow
heavier, the work done there being continually on the in-
crease as is shown in this Report. More subscribers are
badly needed, and the Treasurer hopes that those
interested in the work carried on by the L.M.B.C. will do
what they can to help to increase the list.

Edwin Thompson,

Hon. Treasurer.

1, Croxteth Grove,

Liverpool.

December, 1909.

MARINE BIOLOGICAL STATION AT PORT ERIN.

59

SUBSCEIBEES.

£ s.

Beaumont, W. I., Citadel Hill, Plymouth ... 11

Briscoe, F. W., Colby, Isle of Man ... .. 0 10

Brown, Prof. J. Campbell, University, Liverpool.. 1 1

Browne, Edward T., B.A., 141, Uxbridge-

road, Shepherd’s Bush, London ... ... 1 1

Boyce, Sir Eubert, F.E.S., University, Liverpool 1 1

Brunner, Mond & Co., Northwich 1 1

Brunner, Sir John, Bart., M.P., Silverlands,

Chertsey ... ... ... ... ... 5 0

Brunner, J. F. L., M.P. 23, Weatherley Gardens,

London, S.W. ... ... ... ... ... 2 2

Bullen, Eev. E. Ashington, Heathside-road, Woking 1 1

Caton, Dr., 78, Eodney-street, Liverpool... ... 11

Clubb, J. A., Dr., Public Museums, Liverpool ... 0 10

Crellin, John C., J.P., Andreas, I. of Man... ... 0 10

Crosfield, Harold G., Fulwood-park, Liverpool ... 11

Dale, Vice-Chancellor, University, Liverpool ... 11

Dixon-Nuttall, F. E., J.P., F.E.M.S., Prescot ... 2 2

Eliot, Sir Charles, University, Sheffield ... ... 1 1

Ellis, E. Williams, Chwilog, N. Wales ... ... 1 1

Gaskell, Holbrook, J.P., the late, Woolton Wood... 1 1

Halls, W. J., 35, Lord-street, Liverpool ... ... 1 1

Headley, F. W., Haileybury College, Hertford ... 11

Herdman, Prof., F.E.S., University, Liverpool ... 2 2

Hewitt, David B., J.P., Northwich ... ... 1 1

Hickson, Prof., F.E.S., University, Manchester ... 11

Holland, Walter, Carnatic Hall, Mossley Hill ... 11

Holt, Alfred, Crofton, Aigburth, Liverpool .. 2 2

Holt, Alfred, Dr., Crofton, Aigburth, Liverpool ... 10

Holt, Mrs., Sudley, Mossley Hill, Liverpool ... 2 2

Holt, P. H., Croxteth-gate, Sefton-park, Liverpool 1 1

d.

0

6

0

0

0

0

0

0

0

0

6

6

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Forward

... £36 19 6

60 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

n

SJ

Forward... ... 36

Hoyle, Dr. W. E., Museum, Cardiff ... ... 1

Isle of Man Natural History Society ... ... 2

Jarmay, Gustav, Hartford, Cheshire ... ... 1

Lever, W. H., M.P., Thornton Hough, Cheshire 1

Lewis, Dr. W. B., W. Biding Asylum, Wakefield... 1

Livingston, Charles, 16, Bruuswick-st., Liverpool 1
Manchester Microscopical Society... ... ... 1

Meade-King, K. E., 4, Oldhall-street, Liverpool... 0
Mond, E., Sevenoaks, Kent... ... ... ... 5

Monks, F. W., Warrington... ... ... ... 2

Muspratt, E. K., Dr., Seaforth Hall, Liverpool ... 5

Narramore, W., Cambridge Avenue, Great Crosby 1
O’Connell, Dr. J. H., Dunloe, Heathfield-road,

Liverpool ... ... ... ... ... 1

Petrie, Sir Charles, Devonshire-road, Liverpool ... 1

Eae, Edward, Courthill, Birkenhead ... ... 1

Eathbone, Mrs. Theo., Backwood, Neston... ... 1

Eathbone, Miss May, Northumberland-street,

London ... ... ... ... ... 1

Eathbone, Mrs., Green Bank, Allerton, Liverpool 2
Eoberts, Mrs. Isaac, Thoinery, S. et M., France ... 1

Eobinson, Miss M. E., Holmfield, Aighurth, L’pool 1
Simpson, J. Hope, Ivy lodge, Aighurth, Liverpool 0
Smith, x\. T., 43, Castle-street, Liverpool... ... 1

Tate, Sir W. H., Woolton, Liverpool ... ... 2

Thompson & Capper, 4, Lord-street, Liverpool ... 1

Thornely, Miss, Nunclose, Grassendale ... ... . 0

Thornely, Miss L. E., Nunclose, Grassendale ... 2

Timmis, T. Sutton, Cleveley, Allerton ... ... 2

Toll, J. M,, 49, Newsham-drive, Liverpool ... 1

Walker, Alfred 0., Ulcombe Place, Maidstone ... 3

Watson, A. T., Tapton-crescent, Sheffield... ... 1

s. d.
19 6
1 0
2 0
1 0
1 0
1 0
1 0
1 0
10 0
0 0
2 0
0 0
1 0

1 0
1 0
1 0
1 0

1 0
0 0
1 0
0 0
10 6
1 0
2 0
1 0
10 0
2 0
2 0
1 0
3 0
1 0

Forward

£83 0 0

MARINE BIOLOGICAL STATION AT PORT ERIN.

61

£

s.

d.

Forward .

. . .

83

0

0

Whitley, E., Clovelly, Sefton-park, Liverpool

2

2

0

Weiss, Prof. F. E., University, Manchester

1

1

0

Wiglesworth, Dr., Eainhill

. . .

1

1

0

Wragg, Sir W., D.C.L., Port St. Mary, Isle of IVfan

1

1

0

Yates, Harry, Shudehill, Manchester

...

1

1

0

Less

£89

6

0

Subscriptions paid in 1908 £1 11

6

Do. unpaid... ... ... 9 19

6

11

11

0

£77

15

0

Add

1908 Subscriptions received ... ... £4 4

0

1910 do. do. ... ... 1 1

0

5

5

0

£83

0

0

Subscriptions for the Hire of “ Woek-Tables.”

Victoria University, Manchester £10 0 0

University, Liverpool ... 10 0 0

University, Birmingham ... ... ... ... lo 0 0

£30 0 0

The Naturalist’s Dredge.

THE LIVEEPOOL MARINE BIOLOGY COMMITTEE.

62

TRANSACTIONS LIVERPOOL RIOLOGICAL SOCIETY.

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COOK & LEATHER,

Chartered Accountants.

63

Rfport on the Investigations carried on during 1909
in connection with the Lancashire Sea-Fisheries
Laboratory at the University of Liverpool, and
the Sea-Fish Hatchery at Piel, near Barrow.

Diawn up by Professor AV. A. Herdman, F.P.S., Honorary
Director of the Scientific Work ; assisted by Mr.
Andrew Scott, A.L.S., Resident Fisheries Assistant
at Piel; and Mr. James Johnstone, B.Sc., Fisheries
Assistant at the Liverpool Laboratory.

(With plates and text figures.)

Contents. page

1. Introduction (W. A. H.) _ 53

2. Sea Fish Hatching at Piel (A. S.) 7I

3. Classes, Visitors, &c., at Piel (A, S.) - - - . 74

4. Internal Parasites of Irish Sea Fishes (J. J.) - - - 78

5. Report on Plaice Measurements (J. J.) - . . . iQO

6. Report on Hydrographic Observations (Dr. H. Bassett) - 185 ‘

7. The Flow of Water through the Irish Sea (Dr. H. Bassett) 210

8. Report on Temperature Observations (J. J.) - - . 220

9. Note on the Flookburgh Cockle Beds (A. S.) - - - 248

10. Intensive Study of the Plankton around the South end
of the Isle of Man— Part III (W. A. H., A. S., and
W. J. Dakin) - - 255

INTEODUCTION AND GENERAL ACCOUNT OF
THE AVORK.

In presenting this Annual Report (the IStli of the
series) upon our scientific work to the Committee, I wish,
as usual, to make a few comments upon the more special
and detailed articles that follow, and to call attention to
any matters in the present condition of sea-fisheries
research to which the special notice of the Committee
should be directed.

AA hen the last Report was published the organisa-

E

64 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

tion, equipment and work of our scientific department had
just been reported upon very fully by the Treasury
Committee which sat two vears a^o under the chairman-
ship of Mr. H. J. Tennant, M.P. I think it may be said
that our arrangements generally were approved of, and
that it was felt by the Committee of Enquiry that local
effort on the West coast was worthy of recognition and
Government support. No action has, as yet, been taken
upon the report of Mr. Tennant’s Committee.

A change of considerable importance is, however, at
present being brought about in the organisation and
direction of official sea-fisheries research in this country,
which it is to be hoped may lead to the West coast
receiving in the near future somewhat the same measure
of recognition and financial support as has been given
during the last decade to similar scientific fisheries work
on the eastern and the southern coasts of England.

It is to be hoped that before long under the new
auspices a detailed survey of our British fishing grounds,
and of all waters within the territorial area, will be
undertaken, and it is essential that such work at sea as
has been carried on of late — for example, by our own
Committee in the Irish Sea — should be continued, and
even increased and improved. Almost every department
of our work requires further financial support. We
require a Naturalist to take charge of the observational
work on the “ James Fletcher,” and we require a
Chemical Assistant to carry on the investigations which
have been so kindly undertaken for us in the past by
Dr. Bassett. A more detailed statement of the existing
laboratory and other scientific equipment for sea-fisheries
investigation, now available for public service on the
shores of the Irish Sea, was given in the Introduction to
our last Report, and need not now be repeated.

SEA-FISHERIES LABORATORY.

65

Work at Piel.

Mr. Scott supplies his usual short article giving the
results of the fish hatching at Piel during the past season.
There is no change to record. The apparatus and the
supply of adult fish is the same as it has been for some
years, and the total number of young flat fish set free,
nearly 13^ millions, is practically the same as on several
former occasions. The spawning in the Piel hatchery
appears to take place definitely a little later in the season
than that at Port Erin in the Isle of Man. I may remind
the Committee that at the Port Erin hatchery last season
over seven millions of young plaice were successfully
hatched and set free in the open sea. Both Fisheries
Authorities — that of Lancashire and that of the Isle of
Man — are to he congratulated on the co-operation of the
other in thus adding to the available stock of young flat
fish on the common fishing grounds.

The four usual classes for fishermen were held this
year, thus enabling 45 men in the administrative county,
besides 13 others, to attend the instruction given by
Mr. Johnstone and Mr. Scott at the Piel Laboratory. A
change was made this year in regard to the fourth class
whereby, with the co-operation of the Lancashire
Education Committee, some instruction in Navigation as
applied to fishing vessels was given to a set of men
working on the Fleetwood trawlers with, it is said, very
satisfactory results. It is gratifying to learn that a
number of the students subsequently passed their Board
of Trade examinations, and the experiment of providing
this instruction in connection with the marine biology
classes will probably be repeated.

A considerable part of Mr. Scott’s time not required
for routine official duties, such as the fish hatching and

66 TRANSACTIONS LIVERPOOL BIGLOGJCAL SOCIETY.

tiic Hshcrmcn’s classes, lias been occupied in working out
the microscopic quantitative resulls ol‘ the plankton
collections made by myself and others from the seas to
the South and AVest of the Isle of Man, and this work is
again, as in the last two years, incorporated in our joint
paper on “ Intensive Study of the Plankton ” (Part III.)
which will be found at the end of the Ileport.

Mr. Scott has further devoted some time to the
examination of the shell-fish beds of his neighbourhood,
and I have re-printed a short report on the Flookburgh
cockle-beds which he drew up for our last Quarterly
Peport to the Scientific Sub-Committee.

Mr. Johnstone has carried on Ins work partly at Piel,
partly at sea, and partly in the Liverpool laboratory, and
his results will be seen in several of the articles in this
Ileport. He has continued his work on the internal
parasites of some of our local fishes — such as the Skate —
and this forms the subject of one of the papers below.

Measurements of Plaice.

One of the most extensive articles in this Report is
an account by Mr. Johnstone of the measurements of
many thousands of Irish Sea plaice which have been made
by our stafi; at sea during the last couple of years. The
object of this im^estigation is to get information with
respect to the sizes of the plaice inhabiting the various
fishing grounds in the district. The results of the
trawling experiments and the statistics recorded in the
past are not sufficiently exact and definite, so far as the
size of the fish caught is concerned, to be of much value.
This gap in our knowledge is now being filled up, and
the statistics obtained during the last two years include
individual measurements of nearly 100,000 plaice.

In the summary of this work which Mr. Johnstone

SEA-FISilEKlES LABOKATOKi’ 67

gave in the last Quarterly Keport, he directed attention
to the following points : —

(1) The prevalent, or modal, lengths of the plaice
taken month by month on the various grounds by means
of a G-inch trawl net. Those from flock Channel, in the
Mersey, were the smallest by far, and those from Eed
AVharf Bay, in December, were the largest, with the
exception of some catches made off New Quay, in
Cardigan Bay. The percentages of fish of each length,
in centimetres, are given in the Ileport. The lengths in
inches can be obtained by dividing the lengths in centi-
metres by 2^.

(2) The variation in length from month to month.

(d) The variation in “ condition ” from month to

month, and on the various fishing grounds. As a rule the
condition was worst, in the case of immature fish, in
January and February, and best in July and August.

(4) The small percentage of sexually mature, or
spawning, fishes taken in inshore waters — except in Luce
Bay, and in the Firth of Clyde.

(5) The ages of the fish, the great majority of the
plaice in the inshore grounds off the West Coast of
England and Wales being less than three years old.

(6j The influence of the size of the trawl-net mesh.
In spite of the enormous numbers of small plaice taken by
the G-inch traw] mesh in some areas, like Lock Channel
foi instance, there is no clear evidence for the conclusion
that the G-inch mesh is wastefully destructive. The
plaice are small, and are below the normal in condition ”
because they are so abundant. If they could be thinned
out " by transplantation it might be of advantage to the
fisheries in general to enforce the 7-inch mesh. But so
long as they cannot be transplanted, it is open to doubt
whether the use of the larger mesh would lead to any

68 TRANSACTIONS LIVERROOL BIOLOGICAL SOCIETY.

improvement, and it would certainly diminish the takings
of the inshore fishermen.

Future investigations may, however, lead one to
modify this opinion. If, after several years’ employment
of the 6-inch net, the plaice w’ere, on the whole, to become
smaller, the continued use of the latter net might be held
to be injurious to the fisheries. The present investiga-
tions ought therefore to be continued, and no doubt will
be. The results obtained are bound to be of value in
relation to regulations of the trawl-net mesh.

It is pleasant to record that this work of the measure-
ment of the plaice captured has been conscientiously and
carefully carried out by Capt. Wignall and his Officers,
and by the Bailiffs in charge of the districts.

Hydrography.

As on former occasions, Dr. Bassett, of the University
Chemical Department, has very kindly taken the trouble
to examine our samples of sea-water and report upon their
salinity. Dr. Bassett contributes two articles to this
Ileport, and in the first of these he discusses the main
results obtained from the periodic hydrographic cruises
made during 1909 ; while Mr. Johnstone in the next paper
gives an account of the temperature observations made
on the same cruises, and from some other data. The effect
of the distribution of temperature and salinity upon the
movements of fishes in our seas is still to be determined,
and such papers as those now presented by Dr. Bassett
and Mr. Johnstone are important contributions to the
subject. The accord which Dr. Bassett points out betw^een
the hydrographic observations and the general weather
conditions of the British Islands is most interesting. He
concludes with the hypothesis that the peculiar weather

SEA-nSHERIES LABORATORY.

eg •

of the last year is directly traceable to the late arrival of
the Gulf Stream Drift, coupled with its unusually low
temperature (due probably to greater admixture with
Arctic water of low salinity)”; and bases upon this the
proposition that, after further work, it may prove possible
to predict the general character of the summer and
autumn of any year from hydrographic observations made
during February and March in the Irish Sea and English
Channel, and similarly the probable nature of the
succeeding winter, from observations made during the
summer.

In his second paper. Dr. Bassett discusses fully the
view which he had referred to in former reports that there
is a flow of water from South to North through the Irish
Sea. He points out that some writers on hydrographical
conditions in British seas seem to think that exactly the
reverse current exists ; and then he gives his data leading
to the conclusion that, without any doubt, the water does
actually flow from South to North through the Irish Sea
as a whole — the current passing to the East of the Isle of
Man.

Plankton.

My own contribution to this Deport is the result of
almost continuous daily work at sea during the Easter
and a part of the summer vacation, testing plankton nets
and other apparatus, and collecting samples of the
organisms in the sea-water, along with samples of the
water at various depths and sea-temperatures. This work
was carried on from Port Erin as a centre, out to the
middle of the Channel between Ireland and the Isle of
Man and down to depths of 76 faths. In this work at sea,
and also in the subsequent laboratory work ashore, I have

70 TllAXSACTlOiN'S LIVEIU'OOL BIOLOGICAL SOCIETY.

been ably assisted by Mr. W. J. Dakin and Mr. WiHiani
Riddell. The results obtained will be found in Part 111
of tbe Plankton jiaper at tlie end of tins Jleport.

Shellfish and Pollution.

Tbe state of tbe law in regard to tbe pollution of
sbell-bsb beds by sewage is still a menace to tbe public
bealtb and a reproach to civilisation. Tbe necessary
legislative reform will jio doubt come sooner or later;
but if tbe Sea-Fisberies Local Autborities can do
anything further to secure more immediate attention to
die evil and to insure its removal this }^ear or next year
in place of a decade hence, their action will deserve tbe
gratitude of tbe community they represent and will
receive tbe approval of posterity.

W. A. Herdmax.

Fisheries Laboratory,

University of Liverpool,

March loth, 1910.

SEA-FISHERIES LABORATORY.

71

FISH HATCHING AT IHEL.

13 Y Andrew Scott.

The results from the fish hatching conducted in the
Spring of 1909 were almost similar to those obtained hi
1907 and 1908. The maturing plaice were collected in
the closed area of Luce Bay by our Fisheries steamer
S.S. “ -Janies Fletcher/’ and we are very much indebted
to the Fishery Board for Scotland for granting us per-
mission to trawl in this protected fishing ground each
year. It ensures that a supply of adult plaice will be
secured in a very limited time, and consequently they can
be conveyed to Piel under the most favourable conditions.
Without such a privilege it would be almost impossible
to get satisfactory fish ; at any rate, it would necessitate
spending several days at sea trawling in all directions,
and consequently the captured fish would be landed in a
very exhausted condition. The parent flounders were
caught in the vicinity of Piel, as usual, by the police
cutter stationed in the northern division of the Lancashire
district.

The fish commenced to spawn on March 4th, and the
first fertilised eggs were obtained five days later. The
spawning lasted for two months. During that time one
million four hundred thousand plaice eggs were obtained,
and thirteen million eight hundred thousand flounder
eggs. The incubation of the eggs was carried out in the
Dannevig hatching apparatus, and Ihe resulting fry were
afterwards liberated in the sea. The parent fish were set
tree in the channel adjoining the establishment.

72 TRANSACTIONS LIVERPOOL JOOLOGICAL SOCIETY.

The following tables give the number of eggs
collected, and of the fry hatched and set free on the dates
specified : —

Plaice {Pleuronectcs platessa, Linn.).

Eggs Collected.

Fry Set Free.

March

9

... 20,000

17,500

March

26

12

... 30,000

26,000

33

15

.., 45,000

40,000

• • •

3 3

31

) J

17

... 50,000

44,000

33

33

55

19

... 65,000

57,500

33

3 3

} 5

22

... 70,000

62,000

April

6

? J

24

... 75,000

66,500

33

33

1 )

26

... 80,000

70,000

33

3 3

J 5

28

... 80,000

70,000

33

12

) )

30

... 85,000

75,000

« • •

33

33

April

1

... 90,000

- 79,000

33

53

J ?

3

... 95,000

84,500

33

19

) j

6

... 95,000

84,500

33

33

3 3

8

... 90,000

79,000

33

33

33

12

... 85,000

75,000

33

24

33

14

... 80,000

70,000

33

33

3 3

16

... 75,000

66,500

33

30

33

19

... 60,000

51,500

• • •

33

33

33

21

... 55,000

47,500

. . •

May

14

33

26

... 40,000

34,500

. . •

33

33

33

30

... 25,000

22,000

22

May

5

... 10,000

8,500

33

33

Total Eggs 1,400,000

1,231,000

Total Fry.

SEA-FISIIERIES LABORATORY.

73

Flounder {Pleuronectes Jicsus, Linn.).

Eggs Collected.

Fry Set Free.

March

9

.. 150,000

133,000

. . . March

31

12

.. 200,000

177,000

. . • yy

y y

15

.. 350,000

300,000

... April

6

17

.. 450,000

400,000

... , j

yy

y

19

.. 650,000

580,000

... yy

y »

yy

22

... 650,000

580,000

... yy

12

yy

24 '

... 700,000

600,000

... j j

yy

26 ,

... 800,000

712,000

... yy

/ y

yy

28 ,

... 850,000

757,000

... yy

19

30 .

... 950,000

846,000

... yy

y y

April

yy

1 ,

... 950,000

846,000

... yy

3

...1,000,000

887,000

yy

24

6

... 900,000

800,000

... ,,

y y

y y

8

... 900,000

800,000

... yy

yy

12

... 900,000

800,000

... yy

30

yy

14 ,

... 850,000

757,000

. yy

y y

16

... 650,000

580,000

... yy

yy

19 ,

... 600,000

530,000

. . . May

14

yy

21 ,

... 450,000

400,000

... yy

yy

y y

26

.... 350,000

300,000

... yy

y y

30

... 350,000

300,000

22

May

5

... 150,000

133,000

... yy

yy

Total

Eggs

13,800,000

12,218,000

Total Fry.

Total Number of Eggs ...
Total Number of Fry

... 15,200,000
... 13,449,000

74 TKAiNSACTlOJNS LIVERPOOL JilOLOOlCAL SOCIETY’.

CLASSES, VISITORS, &c., aT PIEL.

13y Andrew Scott.

Lour classes for fisliernieu were held iu the Sprijig of
1DU9. The Education Committee of the Lancasiiire
County Council voted the usual money grant, whicli
enabled forty-five fishermen residing in the administrative
County to receive studentsiiips and attend a course of
instruction at the Piel Marine Laboratory. The Cheshire
Education Committee sent four men, and the Southport
Education Committee also sent four. The Blackpool
Education Committee again sent three men. The
Education Committee of Birkenhead sent tsvo Tranmere
fisliermen. Altogether fifty-eight men attended the
classes and received instruction in elementary Marine
Biolog}L The studentsliip holders were divided into four
classes — three of fifteen each, and one of thirteen, as
shown by the following lists : —

First Class, held March 8th to 19th. — Jolin Hutton,
Flookburgh; liichard Stackhouse, Bolton-le-Sands ;
John Willacy, Morecambe ; John Mount, Morecambe ;
Samuel Baxter, Morecambe; Jas. Wm. Gardner, Sunder-
land Point; William Parkinson, Blackpool; Ilichard
Cornall, Blackpool; P. Westhead, Blackpool; Alfred
WJiiteside, Lytham ; George Henry Oxley, Lytham ;
Thomas Wareing, Banks; l^aul Wareing, Banks; John
Kay, Tranmere ; Arthur Shaw, Lower Tranmere.

Second Class, held March 22nd to April 2nd. — Harry
IT'octer, Askam; John Thompson, lloosebeck; William
Bayliff, Baycliff; John Pelph, Ulverston; Michael
Johnson, Ulverston; AV. Jlenson, Flookburgh; Edward
Burrow, Flookburgh; Adam AVoodhouse, AIore(*ambe ;
Samuel Houghton, Alorecambe ; John Cocking, Alore-
cambe ; John Hadwen, Aiorecambe; Edward Ainsworth,

SEA-rivSlIERIES LAJiORATORT .

75

Knott End, Ele'etwood ; William Parkinson, Hambleion;
James Aughton, Banks; Hieliard Johnson, Banks.

Third Class, held April 19th to 30th. — Thomas
Cocking, Morecambe ; Walter Hadwen, Morecambe ;
Johnson Baby, Morecambe; Thomas Wmodhonse, More-
canibe ; Richard Laytham, Lower Heysliam ; William
Leadbetter, Junr., Banks; William Bridge, Jiinr.,
Banks; Peter Wright, Soiithj^ort; Geoffrey Wright,
Southport; William South worth, Southport; Thomas
Halsall, Southport; Janies Murray, Egremont; William
Cross, Kew Brighton; Thomas Matthews, Junr., Neston;
William Mealor, Junr., Parkgate.

Fourth Class, held May 3rd to 14th. — William
Annison, Thomas Bailey, Edward Colley, Thomas Colley,
P. W. Jennings, James Wilson Meadows, Charles
Radford, Horace Ross, William Roskell, Arthur Suker,
James Sumner, Thomas Whalley, G. Wilson — Fleetwood.

The course of instruction given hitherto in the
fishermen’s classes has been mainly in general Marine
Biology, with special reference to the structure, life and
habits of the more important fish and shellfish. The
Scientific Sub-Committee, with the co-operation of the
Lancashire Education Committee, decided that an
attempt should be made in one of the classes held during
the Spring of 1909 to combine the course of Marine
Biology with instruction in navigation as applied to
fishing vessels. The fourth class of the series was
therefore made a special one, and was attended by
fishermen employed on trawlers working out of Fleetwood.
Preference was given to men possessing the necessary
qualifications in deep sea fishing vessels which enabled
them to sit for the Board of Trade examinations for
certificates as second hand or skipper of a fishing vessel.
The first lesson of each day was confined to general

7() TRANSACTIONS LIVPmPOOL BIOLOGICAL SOCIETA".

Marine Biology, and was conducted in the usual manner.
The County Navigation Instructor took charge of the
class in the afternoons, and two lessons were given eacli
day in navigation, viz., 1.30 to 3.30 p.m. and 5 to 0 p.m.
The results of tlie experiment appeared to be quite
satisfactory, and a number of the students passed at tlie
Board of Trade examinations held at Fleetwood sliortly
after the classes terminated.

The usual thanks to the Sea-Fisheries Committee and
to the various Educational Committees, were proposed
and carried by the fishermen at each class.

One class in Nature Study for school teachers was
conducted during the months of April and May. The
class Avas organised by the Barrow Education Committee,
and was attended by teachers belonging to their schools.
The course of instruction was the same as that mentioned
in the Annual Report for 1907.

Dr. Das, on behalf of the Bengal Government, visited
the establishment early in March. Dr. H. T. Bulstrode,
Medical Officer to the Local Government Board, made
an inspection of the various se^A^age outfalls in the district
and visited the Laboratory in March. I accompanied him
in his survey of the Barrow outfall, and of the course of
the effluent along the shore of the channel.

A large party of Members of the Lancashire Sea-
Fisheries Committee and of the various Educational
Committees of the County, visited the establishment and
saAv the fishermen at work. Short addresses to the men
were given by the visitors. The party was organised by
Mr. James Fletcher, but he was unfortunately unable to
be present. The members of the St. Matthews’s Mutual
Improvement Society visited the Laboratory during the
Easter Holidays. Mr. A. Harris, one of H. M. Inspectors
of Evening Schools, visited the classes for the purpose of

SEA-FISHERIES LABORATORY.

77

reporting on the work. Dr. H. L. Snape, Director of
Education to the Lancashire County Council, visited the
Navigation Class.

A number of interesting Memoirs of the Indian
Museum have recently been presented to the Library at
Piel by Dr. Annandale, the Superintendent of the Indian
Museum, Mr. E. W. L. Holt, the Scientific Adviser to the
Irish Fisheries Department, has, as usual, sent numerous
reprints of papers from the Eeports on the vSea and
Inland Fisheries of Ireland. The United States Fisheries
Department, the Smithsonian Institution, the Trustees of
the British Museum, &c., have also supplied valuable
contributions to our stock of literature.

78 TRANSACTIONS LIVERPOOL RIOLOGICAL SOCIETY.

liSTEKNAL PARASl'l'ES OF FISHES FROM THE
IRISH SEA.

By Jas Johnstone.

CONTKNTS.

I.~ LEBOURIA IDONEA, Nicoi.l.

II.— PROSTHECOBOTHRTUM DUJARDINII (van Bknedkn).

III.— THE GENUS ECHENEIBOTHRIUIM, van Bknedmn.

(1) Lebouria idonea, Nicoll. "

Habitat: Intestine of Calliojiynius lyra, ^rorecanibe

Bay.

The present species is the type-form of a new ^enns
proposed by Nicoll for the inclusion of a Trematode found
by him very regularly, and in large numbers in the
intestine of the Cat-fish, Anarrhichas lu'pus, and less
frequently in the stomach. It is certainly rare in Irish
Sea fishes, and I have only found one specimen so far in a
(Jommon Dragonet caught in the shrimp-trawl in Ulverston
Channel, in Morecambe Bay.

Measurements of the specimen are as follows :
Length : 0‘87 mm.

Breadth : 0*39 mm.

Transverse diameter of oral sucker: 0T3 mm.

,, ,, ,, ventral sucker : 0'3 mm.

Nicoll’s specimens varied from 1*5 to 2 -5 mm. in length
and from 0*7 to 10 mm. in breadth, and are therefore
considerably larger than the specimen described here.
There are also some other differences, but I think it very
probable that the species is the same in both cases, my
specimen being apparently immature.

* “ Studies on the Digenetic Trematodes,” Quart. Journ. 3Iicrosc,
Science. Vol. LIII, Pt. 3, May, 1909, pp. 441-451 ; PL 9, fig. 9.

S E A- FIS HEMES L ABOIlATOliY .

79

The worm is represented in fig. 1, p. 79. The pre-
servation was not good, and there is evidently some
distortion. Bearing this in mind there is a close similarity
between my figure and NicolTs. The oesophagus and
intestinal rami were not seen. The anterior part of the
animal is greatly contracted, so that the cirrus-pouch and
vesicula seminalis, which lay immediately in front of the
ventral sucker were not seen clearly enough to be figured.

The testes are very prominent and are placed about half-
way between the posterior margin of the ventral sucker and
the extremity of the body. They are elongated transversely
and have very much the same proportions and appearance
as in NicolTs figure. The vitellaria are very conspicuous,
more so than in NicolTs specimens. They lie along each
side of the body and behind the testes, with a few follicles
extending in front of the ventral sucker. The vitelline
ducts were also made out very clearly. The two efferent
portions pass transversely towards the centre of the body.

Fig. 1. Lehouria idonea, Nicoll. Mag. 63 dia.

F

80 TRANSACTIOiXS LIVEIU’OOL J510L0GICAI. SOCIKTV.

;it about the middle, and join to form a large yolk reservoir.
This also is shown in NieolTs figure, but the reservoir
does not appear to have been as large in his specimens as
in mine. The ovary and receptacnhim seniinis lie on the
right side of the body in front of the testes. No trace of the
uterus could be made out, but the specimen contains one
egg lying apparently near the yolk reservoir. The
diameters of this are ()‘T9 by 0 47 mm., almost exactly the
sizes given by Nicoll for his type specimens.

(2) Prosthecobothrium dujardinii, (van Beneden)."

Habitat : large intestine of J^aja maculata, Cardigan

Bay.

This cestode is apparently very rare in Irish Sea
fishes, and so far I have only seen one specimen. It is
desirable to draw attention to some points in the anatomy
of the species which do not seem to conform to the diagnosis
of the genus. The species was described by van Beneden
as Acanthohothrium dujardinii but was made the type of a
new genus by Diesingt. The characters of the genus
Prosthecohothrium thus formed are : Scolex with four un-
divided bothridia, each having a suctorial appendage at
its posterior extremity ; no accessory suckers on the
anterior margins of the bothridia ; two double hooks on
each of the latter.

The measurements of the worm are : —

Length of strobila, about 10 mm.

No. of proglottides, about 6.

Length of scolex, 0’39 mm.

Length of hooks, 0T3 mm.

Length of longest proglottis, 2T2 mm

Breadth of ,, ,, 0’5 mm.

■* “ Faune littorale de Belgique : les Vers Cestoides.” Nouv. Mem.
Acad. Roy. Belgique, T. XXV, p. 133. PI. X, 1850.

t “ Revision derCephalocotyleen.” Sitzungsher. Acad. Ffm. Wien-,
Math.-Nat. cl. ; Bd. 48, 49, 1864.

SEA-FISHEUIES LABORATORY.

81

The scolex is represented in fig-. 2. There are four A^ery
prominent bothridia each of which projects well out from
the neck.

The latter is very short. There are no accessory
suckers at the summits of the bothridia. Each of the latter
is really divided into three loculi by two transverse, curved
costae, but the most anterior loculus is long, about tAvice
tlie length of the tAvo posterior ones, and it is not apparently

Fig. 2. Prosthecobothrium dujardinii, (van Beneden). A, the scolex;

B, diagram of one bothrium, seen from the side ; C, the hooks.

A and C mag. 76 dia. ; B mag. 154 dia.

concave transversely. The most anterior costa is very
prominent, and tlie second one difficult to see. There
appears to be only one loculus, but close examination
sliows that a costa is concealed in this deeply concaA^e
double loculus. This is shown in fig. 2 A, and the diagram,
fig. 2 C. It forms a cup-shaped structure - the “ appendice
Ires-motile qui a la forme d’un feuille ” of van Beneden.
The bothrium is thus essentially similar to that of

82

TRANSACTIONS LIVERPOOL LfOl.OG ICAL SOCIETY.

Acanihohothriiim and differs in that the accessory suckers
are absent. Jt is similar to the latter forms in that double
books are present, one pair on each botbrium. Tbe books
are represented in ftg. 2 Ik Each consists of two long,
slightly curved, slender spines fused together by tbeii*
bases. This fused median part is not nearly so prominent

Fig. 3. Prosthecohoihrium dujardinii, (van Beneden) ; Terminal
proglottis. Mag. 51 dia.

as is represented in van Beneden’s figure. Tbe hooks
stand well out from tbe face of tbe botbrium.

The terminal proglottis — the only one in the strobila
which was mature — is represented in fig. d. The posteidor

SEA-FlSIiEKIES LAEUllATOEY.

83

extremity is pointed and tlie ovary is situated here ; it is a
bi-lobed structure tapering to a point at its posterior
margin. The oviduct and uterus were not well enough
seen in the single preparation available to be figured.
Probably they were insufhcientlj^ developed, and it is very
likely that complete maturation of the female organs takes
place in this, as in so many other tapeworms, after the
proglottis has dehisced from the strobila and is free in the
alimentary canal of the host. Perhaps there may have
been free proglottides in this particular fish, but they were
not identified. The vitellaria form two bands of follicles
distributed along the margins of the proglottis, and the
ducts pass off from their posterior extremities and run
obliquely backwards, joining to form a small yolk
reservoir.

The testes are about 24 in number and lie mainly on
the lateral parts of the proglottis, but a few are distributed
in the median regions of the latter ; they are comparatively
large spherical bodies. The cirrus-pouch is very large and
is almost exactly median; within it is a comparatively
long cirrus, armed with short, blunt, straight spines for
the most of its length. This is continuous with the
vesicula seminalis which lies coiled up in a compact mass
between the cirrus pouch and the anterior extremity of
the proglottis.

The genital aperture is lateral and nearly half-way
between the ends of the proglottis. There is a well-marked
vagina, which is dilated termina]ly. The duct passes back,
being coiled loosely towards the ovary. At its posterior
extremity it is dilated to form a small receptaculum
seminis, and from this a very narrow duct passes back-
wards towards the ovary. The junction of receptaculum
seminis, oviduct and vitelline ducts was not seen.

84 '1 KANSACTlOiNS Ln'KliroOJ- J3R)LO(^K’AI. SOCIETY.

Echeneibothrium, van Beneden.

A larfico number oi; specimens of ceslodes belonging
to ibis genus were obtained from various species of Uay
(luring the j)i*esent year, and it seems useful, in view of
tlie great variability of character exhibited by the various
species belonging to this grou]), to describe these worms
in some detail. The genus Echeneibothrium. is defined by
the presence of four Echeneiform bothria carried on con-
tractile pedicels ; by the absence of any armature of the
bothria; and by the presence of a contractile niyzo-
rhynchus, at the apex of which there is a terminal os.

(3) Echeneibothrium variabile, van Beneden.*

ITis is the typical species. The bothria, pedicels, and
myzorliynchus are highly contractile, and very different
appearances are presented by the worms when they die,
and also according to the mode of preservation employed.
I describe here two forms which appear very frequently in
Irish Sea fishes.

I. Pear-shaped myzorhynchus, with terminal os
leading to a concealed proboscis. Bothria typical in form
and structure. Fig. 4, page 85, represents the appearance
of the scolex of a specimen killed in fresh water and
preserved in formalin. The worm was unstained and was
examined in water. The measurements are : —

Greatest diameter of the scolex: 1‘24 mm.
Diameter of myzorhynchus : 0’58 mm.

Diameter of terminal os : 0*2 mm.

The bothria present the typical structure ; tliev are
leaf-shaped v/ith eight or more transverse, and one longi-
tudinal costae. Their apices are curled over, and in the
bothrium at the lower right-hand corner of tlie figure, one
of the lateral margins is also curled over. The s(*olex is
* “ Vers cestoides,” p. 113, PI. 111.

SEA-FISHERIES LABORATORY.

85

seen from tlie anterior end so that we look down through
the os. Inside the latter the proboscis may be seen. It
is partially divided and shows four distinct lobes.

Fig. 5, page 86, represents another scolex of the same
type. The measurement^ are : — Width, 1'7G mm. ; Length,
0*80 mm. The cestode was killed and preserved in the same
manner as that just described. The pedicels are contracted
to some extent and the bothria are also contracted,
exhibiting a very typical cup-like contour. The myzo-
rhynchus is flattened at the summit.

Fig. 4. Echeneibofhrium variabile, van Beiiedeii ; Scolex seen from
the anterior end. Mag. 60 dia.

Fig. 5 also represents another scolex of the same
type. The worm was killed and preserved as before, but
the bothria are contracted to a much greater degree than in
the two other specimens. It has been stained with borax-
carmine and cleared, and is drawn after it has been
fattened out between the slide and cover-glass. It will be

Til AT^S ACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

8(^)

seen that the terminal os in the myzorhynchus leads into a
kind of atrium in which there is a proboscis. The latter is
bowl-shaped, presenting very much the same appearance
as the large ventral sucker in a Trematode. Its internal
walls are not smooth, but are thrown into lobes by the
contraction of the intrinsic and extrinsic musculature of

Fig. 5. Echeneibofhrium variahile. viiu Beiiedeii ; the upper figure is a
general view of the scolex, the lower figure represents another
scolex jjrepared to show the internal proboscis.

the structure. The wall of the myzorhynclius immediately
round the os is strongly muscAilar, so much so that we may
speak of the presence of a distinct sphincter ; and there are
also longitudinal muscle fibres passing back to their origins

SEA-FISHEKIES LABORATORY.

87

in the basal part of the myzorhynchus. This terminal
sphincter muscle lies on and round the opening of the
proboscis, and it can evidently be contracted so as entirely
to close the os. The figure also shows a series of muscles
originating in the base of the myzorhynchus, and inserted
into the sides of the proboscis. Evidently these must
function as retractors of the latter structure.

Qothy'iurn rn u 5

oFthe pro

Fig. 6. Echeneihothrium variahile, van Beneden. Section of the scolex
passing through the bothridia. Mag. 40 dia.

Eig. (j, page 87, represents a section of a scolex
belonging to this variety of E. variahile. The plane is
transverse and passes through the posterior part of the
scolex, through the pedicels and openings of the bothria.
The specimen was preserved in corrosive-sublimate alcohol,
and the bothria are very much, contracted until the openings

88 TJfANSACTlOiNS LI V KUroUl. J5J01.ULICAL SOCIETY.

iire reduced to narrow sliivs. In tiiis region the greater part
ot tlic scolex consists ot a tine fibrous connective tissue
(oiitaiuing few muscle fibres running mostly at rigbt-
angles to each other from opposite sides ot the scolex, wbicb
is nearly square in cross section at this plane. Jfetween
every two botbria there is a band of stout muscle-bbres ;
these are the bbres represented in surface view in bg. 5 ;
they originate mostly at the junction ot scolex and neck,
but many are continuous with the longitudinal bbres in the
latter part ot the strobila. The canals shown in section
near the botbria are part ot the excretory channels. In
the neck these mostly run axially, but at the base of the
scolex they pass towards the botbria and run in the tissues
of the latter organs.

Fig. 7, page 89, represents a transverse section of the
scolex anterior to the plane ot the section just described.
It passes through the proboscis just anterior to the base of
the latter. The internal wall is thick and bbrous, and next
to this is a rather strong layer ot muscle bbres running
circularly. External to this are the radial bbres arranged
just as in the ventral sucker of a Trematode. The external
wall of the proboscis is also thickened and bbrous, and
inserted into it, at nearly equal intervals, are strong muscle
bundles. These are the retractors of the proboscis, and are
the same structures as are represented in bgs. 5 and G.
A few excretory canals are to be seen in the section. ith
the exception of the outer wall of the scolex which is
rather thick, the remaining tissue is a loose connective
stroma.

Anterior to the plane of this section the anterior lips
of the proboscidial sucker are tree from the internal walls
of the atrium into which the os leads.

II. Aiyzorhynchus large and rosette-like and without
a terminal ns. Bothridia typical.

SEA-FISHERIES LABORATORY.

89

The presence of this complex mj'zorliynchus, and the
variability of the shapes into which it may be thrown by
tiie action of its muscles, often renders the identification of
species of Echeneibothriiim a difficult matter. It often
happens that the terminal os cannot be seen, that the

mvzorhyiichus is large, and flattened out in the transverse
plane, while the bothridia and their pedicels may be very
much contracted. These changes are without doubt caused
by the eversion of the internal proboscidal sucker, and the
reversal of the surfaces of the latter. Then the retractor
muscles, pulling on the walls of the proboscis, throw the
latter into lobe-shaped structures. Tliis radial siructure
can often be seen when looking down on the surface of the
myzorhynchus ; it is shown, for instance, in fig. 4, p. 85,

Pro bo'Sd S / ,

Re.tr CL ctorm usd es
of thei prob.osds

Fig. 7. Echeneihotlirium variahile, van Beiieden.
Section through myzorhynchus. IMag. 110 dia.

90

TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

and it is suggested in van JJeneden’s %. 2, PI. 111."^
Olssont (Tab. I, fig. 15) also represents it very clearly and
ascribes the condition to the real cause. Bulbus apice
expanse (forma singularis horibiis llosariim similis).”]
Fig. 8 represents views of the scolex of an
K. variahile, the anterior aspect of the myzorhynchus on
the right and the posterior aspect on the left, the neck
being bent at a right angle to tlie scolex. The myzo-
rhynclms is nearly round in surface view and it is flattened

Fig. 8. Echeneihothrium variahile, van Benedcn ; the left-hand figure
represents a view of the scolex from beneath, on the right the scolex
is seen from its anterior surface. , Mag. about 35 dia.

greatly to form a disc ; from this aspect the bothridia were
quite invisible. On the anterior surface of the myzo-
rhynchus were one central and six radially arranged lobes.
These structures are very distinct and are raised up from
the surface of the scolex, so that they can be seen when the
latter is looked at from the side. But they are not free from
the myzorhynchus, not even at their apices and in some
cases the sulci between them are very shallow. In yet
* Loc. cit.

t Ada Univers. Lundensis ; Lunds. U nivers. Aarshrijt /dr 1865 ;
Afd. Math.-Natur. IV, Lund., 1866-7.

SEA-FISHERIES LABORATORY.

91

aiiother oestode a soDiewhat sirailai* condition was present,
but the myzorhynchal lobes were asymmetrically arranged,
there being a group of five small ones on one margin ; at
either end of this series a larger lobe, and on the opposite
margin three larger and flatter ones ; there was also a
central lobe. As in the case of the scolex just described
the lobes were low and not free at their apice from the
myzorhynchus.

Beneath these lobate appendages there w^as in the
first specimen, a stout and very distinct rim on the scolex.
This is represented in outline by the margin in fig. 8.
Below this were four suckers. These were sessile, and
there were no traces of pedicels.

At first I was inclined to approximate these specimens
to the genera P olycej)lialus Braun, or P arataenia Linton,
in which there are about sixteen longish tentacles on the
scolex, and, beneath these, four suckers. But the lobate
structures in the specimens which I have described here
can hardly be regarded as tentacles, unless one regards the
amount of contraction as excessive; while the sessile,
sucker-like appendages beneath the myzorhynchal rim are
not at all like the sucker of a Taenia, to which category the
suckers in Polycej)halus and P arataenia apparently belong.
It is evident, from a glance at fig. 8, that the suckers are
bothridia of the Echeneiform type. Only some of the
costae can be seen, and the whole organ is very much con-
tracted. It resembles the bothrium of such a cestode as
Anthoboihrium rather than that of an Echeneibothrium, but
these organs are so versatile that one can hardly regard
even this deviation from the normal form as of importanoo
as a diagnostic character.

I am forced to conclude that these are simply
specimens of Echeneibothrium variabile with the proboscis
everfed through the myzorhynchal os. It is difficult to con-

1)2 THANSACTIOiNS LIVERPOOJ. JilOLOCiJCAI. SOCIETY.

reive wliat merhaiiism is involved in this process; picibably
tlie excretory canals, acting as a waiter vascular system
may be instrumental, and tlic proboscis would tlieii lx*
turned iiiside out in much the same way as the proboscis
of a Tetrarhynchu^ or Xemertine worm is everted. The
longitudinal retractor muscles would then be put on the
stretch, and being inserted in bundles, at intervals round
ibe proboscis, they would pull on the latter so as to throw
its muscular ring into lobes. This contraction would
flatten the myzorbynchus and produce the prominent rim
below the lobes. It would also lead to such distortion as
would obliterate tbe usual form of the bothridial pedicels.
The contraction of the bothridia themselves would
doubtless be correlated with this extensive contraction of
the whole scolex.

The first of these two specimens differs from Echenei-
bothrium with regard to the characters of the strobila.
Part of this is represented in fig. 9. The neck in this
specimen was distinctly bulb-shaped and without segmen-
tation. Then follows a region in which the proglottides
are of the usual form. But posterior to this they are much
longer than they are broad ; a condition very different from
that characteristic of E. variahile. The prominent enlarge-
ment of the proglottides represented in the figure is no
doubt accidental. But the most posterior proglottides again
deviate from the typical form. They are very irregular in
size and shape and almost every one presents a prominent
groove on one of its surfaces, as if the margins of the
proglottis had been turned over. The characters of the
strobila appear to me to present a greater difficulty in the
identification of the cestode as E. variahile, than do those
of the scolex. In the meantime, pending the collection of
more material, it is as well to refer them to this species.

The specimen of E. variahile, the liead of which is

SEA-FISHERIES LABORATORY .

93

represented in fig. 4, was 1]0 nun. in lengtli. At nearlj'^
all points the transverse section ot a proglottis is circular.
The proglottides immediately behind the neck were 0T9
mm. in width by 0'03 in length; and the terminal ones
were about 0’92 mm. in width by 0*48 mm. in length.

Fig'. 9. Echeneibothrium variabile, van Beneden. Parts of a strobila,
tlie posterior proglottides being on the right.

Echeneibothrium dubium, van Beneden^"

I have already figured f this species as a variety of E.
variahile. Further examination of a number of specimens
has, however, shown that this “ variety ” is, in all proba-
bility, the species referred to here. It is not always possible
to observe the os in the myzorhynchus, and occasionally
the latter .structure is so greatly contracted as to present

* “ Memoire sur les Vers Intestinaux.” Suyflemenl to Tome II,
Comptes Rendus, Acad. Sci. Paris, 1858, p. 122, PI. XV.

t Fourteenth Ann, Rept. Lancashire Seal Fish. Lahy. Trans.
Liverpool Biol. Soc., Vol. XX, 190G, p. 310, fig. 19.

94 TRANSACTIONS LTVERl’OOL BIOLOGICAL SOCIETY.

(juite a difterent appearance from^the figures given by van
Jieneden.

Fig. 10, page 94, represents a tnlly expanded
specimen, such as may be obtained by killing the worm in
fresh water and preserving it in weak formalin. In this
specimen the bothridia were carried on rather long,
versatile pedicels arranged in the form of a cross, very
approximately in the transverse plane of the scolex. The
bothridia are situated nearly at right-angles to the axes of

Fig. 10. Echeneihothrium dubium, van Beneden ; A, the apex of
the myzorhynchus ; B, the scolex. Mag. about 60 dia.

the pedicels. Each is leaf-shaped, very nearly oval in
surface view, slightly pointed at the anterior extremity.
They are bent so that their concave surfaces are directed
outwards from the axial line of the strobila. Each
bothrium has 10 loculi, these being formed very distinctly
by five transverse costae on either side, and two median
longitudinal costae. Two of the loculi are terminal. This
arrangement is represented in van Beneden’s fig. 10, but

SEA-FISHERIES LABORATORY.

95

there do not appear to be so many locnli in the botbridia
figured.

The myzorbyncbus is figured separately in fig. 10 A.

It is very difficult to make out the structure of this
organ in whole preparations of the worm, but transverse
sections shew that it is essentially the same as the corre-
sponding structure in E. variahile. The terminal os leads
into a rather long canal which terminates in the opening of
a proboscidial sucker. The latter is represented by the
globular structure in fig. 10 A. It is, however, not
apparently muscular. The very prominent radial and
concentric muscle fibres represented in fig. 5 are quite
wanting, and in their place there is a rather loose connec-
tive tissue. The longitudinal retractor muscle bundles are,
however, represented ; they pass down in the external part
of the myzorhynchus and apparently originate in the walls
of the basal part of the latter.

E cJieneibothrium variabile, E. duhium and E. minimum
thus form a series characterised by the progressive
reduction of a functional myzorhynchus. In the first
species this organ is large and well developed, and the
eversible proboscis contained in it may apparently act as
an actual organ of adhesion. In E. duhium the myzorhyn-
chus is still present, though greatly reduced in size ; and
the contained proboscis is also greatly reduced, and
cannot, apparently, be everted. In E. minimum the
myzorhynchus has entirely disappeared, and it is this
di:fference that appears to me to justify the removal of
the species from the genus in which it was originally
included.

Rhinebothrium minimum (van Beneden).

Habitat : Raia clavata and R. maculata.

The difficulties presented by the systematic characters

G

96 TRANSACTIONS LIVERPOOL RTOf.OGTCAL SOCTE^J'V.

of tlie genus Echeneihotlirium are further illustrated by the
study of the species known as E. minimum, van Beneden* ;
E. gracile, Zschokket; and Rhinehothrium spp. Linton^.
The species E. minimum described by van Beneden is
characterised by the presence of Echeneiform hothridia
divided by transverse, hut not (apparently) by longitudinal
costae ; by the presence of a long neck ; and by the presence
of a group of fairly long spines at the base of the cirrus.
E. gracile has Echeneiform hothridia divided by both
transverse and longitudinal costae ; it has no neck, the
segmentation of the strobila being continued right up to
the scolex ; and it does not possess the group of long spines
at the base of the cirrus. Rhinehothrium resembles the
genus Echeneihothrium in most characters, but it was
founded by Linton to include cestodes possessing Echenei-
form hothridia, but lacking the peculiar myzorhynchus
possessed by such a species as E. variahile.

There is no ambiguity in the descriptions or figures of
the authors quoted. P. J. van Beneden figures the
hothridia of E. minimum most clearly and indicates no
longitudinal costa, but certainly represents a long neck,
and a most distinct group of long spines at the base of the
cirrus. Zschokke, on the other hand, just as clearly des-
cribes and figures his worm as possessing longitudinal
costae, no spines at the base of the cirrus, and no neck.
No one would have difficulty in drawing up a table of
specific differences.

Unfortunately the cestode described here combines

* “Vers Cestoides,'’ p. 114, PL II.

f “ Eecherches sur la Structure anatomique et histologique des
Cestodes.” Mem. VInst. Nat. Genevois ; T. 17, pp. 348-356, PI. IX.
Geneve, 1889.

t “ Notes on Entozoa of Marine Fishes of New England with
descriptions of several new species ” ; Commissioners’ Report for 1887 ;
United^States Commission of Fish and Fisheries, pp. 768-778, Pis. V-
VI. Washington, 1891.

SEA-FISHERIES LABORATORY.

97

both series of characters and I have some difficnlty in
referring to it either, still more in making a new species
distinct from both. But the name E. minimum is an old-
established one, is well-known, and may be adopted, on
the understanding that the form now described does not
quite display the characters connoted by it.

About half-a-dozen of these worms were obtained
from Bay dissected during the fishermen’s classes at Piel
in 1909. Evidently they are rather rare, for this is the
first time that they have been found. They were about

Fig. 11. Rhinehothrium minimum (van Beneden). Two scolices :

A mag. about 70 dia. ; B about 27 dia.

4 to 8 mm. in total length. There were about 12 to 15
proglottides in each of the strobilae; and the largest
proglottis — the terminal one — was about IT mm. in
length. The scolex was about 0’8 mm. in width and about
0'7 mm. in length.

98 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Fig. 11, page 97, represents the general appearance
of the scolex in two specimens. There are four leaf-like
bothridia, pointed at their anterior extremities, and broad
posteriorly. Their lateral margins are rolled over, and
usually anterior and posterior extremities are likewise
rolled over, hut in the opposite direction. This distortion of
thehothrium renders it difficult to study the divisions on its
external surface. But neither in stained nor in unstained
preparations, nor in transverse sections can a longitudinal
costa he seen. There are apparently 7 or 8 Icculi on the
face of the sucker along each side, one loculus being
situated terminally at either end. The costa apparently
cross from side to side, but it is difficult to follow their
course owing to the flexure of the bothrium. Seen as in
flg. 11 A, there appear to be lateral rows of distinct loculi,
but this appearance is due to the optical sections of the
transverse costae. Fig. 11 B, represents another scolex on
a smaller scale and one of the bothridia is seen very nearly
en face and there is no indication of a longitudinal costa.
The latter figure also shows how the bothridia are situated
on distinct pedicels. The latter are strongly muscular,
containing both transverse and longitudinal fibres in their
walls. Fig. 11 A also shows that the segmentation of the
strobila is continued up to the base of the pedicels, that is,
a distinct neck — far less such a long neck as is represented
in van Beneden’s original figure — is wanting.

The proglottides are not figured. They agree in all
respects with both van Beneden’s and Zschokke’s figures,
except for the detail of the armature of the cirrus. There
is no doubt that only one kind of spines is present. The
cirrus was fully extended in one proglottis and most of its
surface was covered with short, slightly curved spines.
No long spines were present at the base.

The absence of a longitudinal costa indicates that the

SEA-FISHERIES LABORATORY.

99

worm is E. minimum ; but the presence of a neck, and the
absence of long cirral spines indicate that it is E. gracile.

Neither van Beneden nor Zschokke apparently
attached much importance to the absence of a myzo-
rhynchus. Yet the presence of this most characteristic
organ is part of the definition of the genus Echeneibothrium.
I follow Linton in his suggestion, that the absence of this
structure justifies the removal of a cestode possessing
Echeneiform bothridia from the genus Echeiieihotliriiim.
Now there is no figure of E. minimum which shows a
myzorhynchus, and the organ is absent in E. gracile also.
I examined the specimens here described very carefully
and could see no part anterior to the pedicels; and there
is no evidence of a proboscidial structure in a series of
sections made from one of the worms. It is true that a
small, knob-like protuberance could be detected, but I
think that this was only a hump on one of the pedicels.
The myzorhynchus in the specimen of E. variahile figured
on page 85, and the rosette-like structure mentioned by
Olsson are very striking and prominent features of the
anatomy of these animals; and even in the specimen of
E. dubium figured on page 94, the myzorhynchus is very
obvious. It seems therefore that we are justified in placing
both E. minimum and E. gracile in a distinct genus, as is
suggested by Linton. Whether or not these tw'o forms are
specifically distinct is a more difficult question.

100 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

REPORT ON MEASUREMENTS OE IRISH SEA
PLAICE MADE DURING THE YEAR 1909.

By Jas. Johnstone.

1. INTEODUCTION.

2. THE DATA : TABLES AND GRAPHS.

3. MODAL SIZES ON THE FISHING GROUNDS.

4. AGE-GROUPS.

5. LENGTH AND WEIGHT.

6. INFLUENCE OF SIZE OF MESH.

7. SEXUAL MATURITY.

I. The data which are tabulated and discussed in the
present Report relate to the measurements of some 55,000
j)laice made during the year 1909. This investigation
was begun in the summer of 1908 and was intended to
yield results which were to be used in connection v ith
plaice-marking experiments. It was found whenever it
was attempted to make a summary of the latter results,
that it would be most advantageous to consider the modal
sizes of plaice inhabiting the various plaice-grounds.
But it was also seen that the results of the measurements
of a large number of plaice and soles would afford data
of the greatest possible value in relation to the question
of the regulation of the trawl-mesh — a matter, which it
is needless to point out, has been the cause of much local
controversy. This latter object has been kept continually
in mind during the progress of the work.

It might be thoaght that the results of the statistics
of fish landed at the ports would supply just the informa-
tion required, but unfortunately this is not the case.
It may be interesting to know what quantities and
values of fish are landed monthly at the ports, but
the really important questions which arise in the
course of such discussions are not answered by the

SEA-FISHERIES LABORATORY.

101

statisticaf returns. We cannot tell, from tlie published
figures, where precisely the fish were caught ; what were
the powers of capture employed in catching them; nor
what were the sizes and condition of the fish.

I think it would be much better if the present system
were supplemented by paying a certain number of masters
of sailing trawlers for making accurate diaries of the
results of their fishing voyages. I would refer here to a
paper of Miss R. M. Lee* on the discussion of such
records made by the masters of several fishing vessels
working from Lowestoft. The methods employed in this
Report are well worth adopting for local use; and it
appears to me that if we had a record of the fishing
operations and results of (say) 40 sailing trawlers working
from Fleetwood, Hoylake and Douglas, a very approxi-
mate picture of the movements and relative abundance
(which is what we want to know, not the quantities
of fish landed) of plaice and soles in the Eastern
half of the Irish vSea, and in the Welsh Bays. These
vessels work over all this area, obviously they go
only where fish are to be obtained, and obviously we
should be utilising the accumulated experience of the
masters — an experience which surely is of the greatest
possible value in the consideration of fish problems.
If, in addition to such records, the system of measure-
ments of sample catches already applied were extended,
we should be in possession of data of great service in the
discussion of fishery regulations. Not only so, but it
might be possible to trace the connection of the move-
ments and abundance of plaice and soles (with other fish,
of course) in relation to the hydrographical conditions in
the Irish Sea — connections which are even now suggested,

Report on the Lowestoft sailing trawler Records, 1903-1906.
International Investigations, Mar. Biol. Assocn., Bept. II, Pt. II, 1904-5,
pp. 89-112, (1909).

102 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

but which cannot be pushed home for want of further
statistical information.

In the meantime much is to be deduced from a
knowledge of the sizes and conditions of plaice caught
on the various fishing grounds; and such data appear to
be the only information we can, at present, obtain that
is of any use in the consideration of the effects of the
trawl-mesh regulations.

The measurements tabulated in this Eeport have
been made by the officers of the Committee : Captain
Wignall and his officers; and the Chief Bailiffs, Messrs.
J. Wright, G. Eccles, and E. Jones; and a good deal is
to be said for the trouble and care taken in preparing
these records. Captain WignalTs measurements refer to
plaice caught practically all over the district ; Mr. Eccles’
figures refer to the Mersey fishing area only; Mr.
Wright’s measurements were made in the Morecambe Bay
area; and Mr. Jones has measured catches in Menai
Straits and Carnarvon Bay. In addition to these
measurements, made on board ship, a number of
additional records have been made by Mr. A. Scott and
myself. Numerous samples of plaice and soles taken on
the various fishing grounds have been sent to the Piel and
Liverpool Laboratory ; and have been examined in much
greater detail than was possible on board ship. This part
of the work is weakest of all. The amount of time
required to examine even 100 plaice thoroughly is con-
siderable, and when we attempt to make any accurate
estimates of the age and the conditions as regards
maturity and nutrition, samples of more than the above
number are necessary.

As a rule the measurements made by the Officers are
very accurate. The lengths of the fish are recorded in
centimetre groups. The use of. inch scales is irritating

SEA-FISHERIES LABORATORY.

103

and troublesome when the subsequent tabulation of the
measurements is made. All the figures given are mean
lengths. The fish is laid on the measuring board and the
division in which its tail falls is noted. All fish between
n and ?i + l cms. are recorded as n cms. The mean length
is then ?i + 0'5 cms. -On board the ‘‘James Fletcher” a
brass pin is stuck into the measuring board opposite the
tail of the fish. The number of pins in each cm. division
is then read off. This method is the most accurate of
all those employed. In most cases the sample of plaice
sent to me for further examination has already been
measured on board the “ James Fletcher.” On receipt
it is ^re-measured and I give in the Table on p. 184 the
results of four of such duplicate measurements. It will
be seen that in two cases the numbers are practically
identical. In the other two cases there is a discrepancy
which is to be expected, and which is due to contraction
of the fish after death. Why it is that this discrepancy
is not always apparent I do not know. Possibly a fish
contracts when rigor mortis sets in, and relaxes again
when this passes off. In the two cases where this dis-
crepancy occurs the mean difference is 0*58 cm., that is
the fish wdien measured by Captain Wignall’s men were
about \ cm. longer than when I measured them.

All the measurements recorded in the Tables on
pp. 153 to 171, were made on living fish. The first thing
done, when the trawl net is cleared, is to measure and
record the plaice and soles. The numbers are then entered
on the log sheets. Sometimes the entire catch is sent to
the Laboratory, but more usually only a part is sent.
These samples are examined for length and weight, so as
to get average weights and values of the coefficient h;
for age, by inspection of the otoliths; for maturity, by
examination of the gonads; and occasionally for food

104 TllANSACTlONS LIVERPOOL BIOLOGICAL SOCIETY.

contents. Sometimes each fish is individually weighed,
but as a general rule all the fish in each cm. group are
weighed and the total and average weights determined.
In all cases a single fish, or a number of such, are
weighed to the nearest gram. It is often difficult to state
definitely the condition as regards, maturity. As a rule
there is no ambiguity in the case of the males : a male
plaice is either mature or immature ; but it is sometimes
difficult to say, at some seasons of the year, w^hether
the females are, or are not mature. Mature females are
regarded as such in which the ovary extends to more
than half way between the first axonost and the root of
the tail.

The question of examining sample catches of plaice
purchased from trawlers was considered and decided
against. The localities of capture in such cases cannot,
as a rule, be accurately ascertained; the fish are often
selected, small ones being rejected; the conditions of the
hauls from which the fish are taken cannot generally be
ascertained ; the fish are usually gutted ; and they may
be iced or uniced. Ho' doubt the examination of fish
landed at the ports may have a certain value; but it
ought to be pointed out that if legislative restrictions are
to be based on statistical results all possible trouble should
be taken to render the latter as accurate as can be. Now
the conditions under w^hich the examination of fish landed
at the ports can be carried out are not such as to make
the investigation a strictly scientific one. All the
measurements of length alone in this report relate to
living fish; and measurements of weight in respect to
length relate to ungutted and uniced fish, and are made
not later than twenty-four hours after capture. Thus
irritating comparisons between “ entire ’’ and “ cleaned ’’
fish, with the uncertainty attaching to the employment of

SEA-FISHERIES LABORATORY.

105

“ constants ” are avoided. Further, the measurements of
length, and the deduction of modal sizes apjply to samples
— that is all the fish taken in one haul of the trawl-net.

What is a representative sample ” ? It would be of
service if there were some criterion or test which might
be applied to a series of measurements of length, and
which would enable us to say whether or not the sample
catch represented truly the whole population of fish
resident on the sea bottom over which the trawl was
dragged. Unfortunately no such criterion exists, and
one can only say that a sample catch is representative if,
on trawling again and again, one gets similar results.
But one cannot do this. Biologists and actuaries, who
have to deal with statistical material, are able to make
conclusions as to the accuracy of the data by employing
frequency-curves. But it will be seen that this test is not
possible in the consideration of the statistics dealt with
in this Eeport. Nevertheless it is possible to determine
roughly whether or not a sample catch with a particular
net is, or is not, normal for the fishing ground and season
of the year considered. An accident to the trawl — the
tearing of the net, or the partial stoppage of the meshes
by accumulations of sea- weed or jellyfishes — is usually
indicated by the measurements. But one cannot be quite
sure whether or not such unusual measurements may not
after all truly represent the fish population on the sea
bottom.

2. THE TABLES AND GRAPHS.

The measurements represent the mean lengths in
centimetres of the fishes. The limits of error are +0*5. In
a large catch, as for instance in some of Mr. Eccles’
figures where there may be several hundreds of fish in
some cm. groups, the limits of error are much smaller

106 TKANSACTI().\S LlVEliroOL inOLOGlCAJ. SOCIETY.

than + 0'5. But in the smaller catches this error may
actually he present. In these latter cases it is more
accurate to “ smooth ” the figures by the use of the
formula

Mean length of group h = ^ ^ ^

this summation and division being applied to every three
contiguous groups in the series.

They are grouped according to locality, beginning
with the more northerly tishing grounds. The numbers
of fish from Luce Bay and the Clyde are small, but are
useful for comparison with the truly Irish Sea fishing
grounds. The fishing grounds off Duddon Buoy, in, and
off Barrow Channel, and in the estuary of the Rivers
Wyre and Lune might possibly be regarded as one natural
area ; nevertheless they are tabulated separately : one
learns to avoid “ lumping ” as much as possible. Black-
pool Closed Ground and the grounds off Nelson Buoy are
probably rather different, but the number of fish caught
is small and the hauls have been combined. The Mersey
area presents marked differences : Rock Channel contains
quite a difiierent kind of plaice from the grounds in Horse
Channel, or near the Mersey Bar. Probably the grounds
near Great Orme’s Head and in Beaumaris (or Conway)
Bay, and in Red Wharf Bay are very similar, but the fish
taken in these areas are separately tabulated. A few
catches are recorded from Carnarvon and Cardigan Bays,
but so far we have not paid much attention to these parts
of the District. The Sketch Chart opposite page 106 gives
the approximate positions of these areas.

All the catches made in each area in each month
have been added together. The month is, of course, a
purely arbitrary division of time, and the ideal method
would be to give the figures for each haul. But

Plate I

Observation Stations in 1909.

% •

SEA-FISHERIES LABORATORY.

107

considerable space is saved by tlie grouping, and no
serious error is involved.

All the Tables from p. 153 to p. 17 1 relate only to
these measurements of length made immediately after
capture of the fish. The actual frequencies are given
under the headings “Nos.,” and then these frequencies
have been converted into percentages of the whole catch
accurate to the first decimal place. Representation of
the frequencies as percentages of the total catch assists in
making comparisons, and enables us to draw graphs to
the same scales of coordinates for all the catches.

The Tables Age-Groups, 1909,^’ which occur on
pages 172 to 178, represent the ages of those plaice
examined according to the conventional grouping : Age-
Group 0 includes fish 0 to 1 year old, I fish 1 to 2 years
old, and so on. The first group is seldom represented
in catches made with a trawl net of 6-inch mesh, and
has not been considered. Age-groups higher than III
are also very sparingly represented in most of the
localities, wfith the exceptions of the offshore grounds
near Bahama Bank, and in Luce Bay and the Clyde
area. “ Lumping ” can only be practised here to a very
limited degree. It is permissible to combine the measure-
ments relating to the same month, though even this
involves error during the period of most rapid growth.
The measurements made during the months January to
March and September to December may, however, be
combined, since growth is minimal during these seasons.
Obviously one cannot combine the results from different
grounds without risk of error.

The Table “ Modal Lengths of Plaice captured hy a
6-inch Trawl Mesh, 1909 p. 179, summarises the
measurements so far as the modal, or characteristic
lengths, are concerned. These lengths are given for each

108 TRANSACTIONS LIVERPOOL RTOLOGTCAL SOCIETY.

fisliing-ground and for each month represented in tlie
statistics. The figures in brackets relate to secondary
modes and indicate that the catch was obviously hetero-
geneous. The method of determination of the modes is
given on p. 11.

Table “ Modal Lengths of Plaice of Age-Groups I
and II, 1909,” given on p. 180, summarises the results of
the age-determinations from inspection of the otoliths.
The methods and results will be discussed later.

The Table “ Values of the Length-W eight Coefficient
h, 1909,” given on p. 179, is an attempt to summarise
the data relating to the conditions of nutrition of plaice
in the Irish Sea. It was hoped that a more complete
series of results would be attained, but in the meantime
this Table may be useful for future comparisons. Average
weights for the fishes examined are not tabulated in the
report : evidently they can be obtained by making use of
the coefficients and the length-weight formula. The
coefficient Tc is

lOOS g
tnl^ ^

when g is the weight of all the plaice in each cm. group,
n the number of fish in each cm. group, and I the mean
length in cms. The results of the Table are discussed
further on p. 143.

The Graphs.

J ust how to graph these series of figures was a matter
of some difficulty. Merely to plot the points given in the
percentage columns of the Tables of length-frequencies
leads to confusion for one does not easily see what are the
positions of the modes, and the curves are, in some cases,
very “ jumpy.’’ Smoothing the curves, as already indi-
cated, simplifies them, but not sufficiently to assist in
estimating the distribution of the lengths.

SEA-FISHERIES LABORATORY.

109

It is quite evident from inspection of tlie series of
length-frequencies that no generalised frequency-curve
can be found which would express the theoretical distri-
bution. I have no doubt that investigation would show
that some of the series might be represented by a curve
belonging to one of Pearson’s types of the generalised
probability curve, and that by an appropriate manipula-
tion of the constants many might be fitted. But the fit
would probably be fictitious, as none of these series deals
with a homogeneous group of plaice. Obviously each
contains fish of Age-Groups I and II, and some include
higher age-groups also. This is the case even when the
frequency-curve is apparently unimodal, and in many
series the curve is obviously multimodal. If a frequency-
curve could be found, which could be represented by an
equation — as in the case of most biometric series — the
study of fish migrations would gain immensely in exacti-
tude, for one could replace the observed distribution of
length by the theoretical distribution, and then modes
and other frequency-points on the curve would represent
the actual distribution with less improbability than the
actually observed values. But this is, apparently, not
the case.

The formula suggested by Edser* helps us in some
respects. It is shown by this writer that, within certain
limits, the distribution of lengths in a catch of plaice can
be represented by an equation of the type log y = A. + })x,
where y is the frequency, x the length, A a constant, and
h the tangent of the angle which the curve makes with
the axis of x. The equation is, of course, that of a
straight line. The whole catch of fish is represented by
two straight lines, except near the mode. One line repre-

* “Note on the Number of Plaice at each Length, in certain
samples from the Southern Part of the North Sea.” Journal
Statistical Society, Vol. LXXI, Part IV, December, 1908, p. 4.

110 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

sents the frequency of the fish at lengths less than that
of the mode, and the other the frequency at lengths greater
than the mode. Now if this relation were of universal
application it would he of immense value, for the work
of fitting a catch of fish to such a curve is simple and
rapid. Further the equation shows that the gradient of
the curve is a constant one ; that is the number of plaice
at any length, say n + lcms., is in a constant ratio to
the number at n cms. Knowing, then, the numbers taken
at any particular length — not too near the mode — we
should be able to calculate what numbers were taken at
most other lengths. The formula would enable us to
estimate the value of the sample.

But it will be seen by plotting the logarithms of the
numbers of fish taken in most of the catches tabulated in
this Eeport, that the equation does not generally repre-
sent the distribution of lengths. One cannot expect that
a close fit would usually be obtained, but it appears to
me that the deviations from the curve are often too great
to be due merely to errors of observation. Probably the
catches consisting predominantly of fish of one age-group
would fit the curve fairly well, but many catches evidently
consist of fish of various age-groups, and the presence of
these contrasting groups is often most distinctly indicated
by the double modes in the frequency-curves. The
equation log y = A + &.r does not describe the distribution
in such catches. If, on the other hand, a large number
of plaice were caught at ditferent times during the year,
and on ditferent fishing grounds, the variations in rate of
growth due to different natural conditions, and the
capture of fish at different seasons of the year would
smooth down the curve and we should have a gross catch
of fish, apparently homogeneous, but not really so. The
equation, while useful in the analysis of commercial

SEA-FISHERIES LABORATORY.

Ill

statistics, does not help us greatly in dealing with true
samples.

By far the best method of graphing the figures is to
integrate the percentage numbers and to plot the values
so obtained. This was suggested to me by Mr. H. J.
Buchanan- Wollaston* and the method has been con-
sistently applied in the analysis of the data obtained.
The frequencies are summed so that any ordinate,
2/„ = So 2/- These values are then plotted in place of
the original figures, and each value of y on the curves
represents the percentage of plaice at and above the
corresponding length represented by x. A glance at the
graphs on pp. 117, 124, will at once show how greatly
the analysis of the figures is facilitated ; and how
regularity is to be obtained from data apparently most
irregular. All the curves are very smooth: the dots
represent the positions of the actual figures; and the
graph can be drawn by inspection without any doubt as
to how it ought to go. One sees at once what is the
dispersion of the group of fish, and what are the modal
sizes.

The latter values are obtained by determining the
points of inflexion on the curves. The graph is drawn
very carefully, employing some mechanical method of
obtaining a line which passes as near as possible to all
the points, with as few changes of curvature as possible.
As a rule this is a matter of little difficulty. The tangent
is then drawn, using a glass ruler so that both sides of the
curve are visible. The curvature is usually very slight
at the point of inflexion, but the points where the tangent
apparently begins to diverge from the curve can usually
be observed fairly accurately, and the actual position of

* The method is applied by Bowley, Ele7nenl8 vi Stahstics, Ed. 2,
p. 155, 1902.

H

112 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

the point of inflexion is found by bisecting the tangent
between the former points. Often there are two points
of inflexion, rarely three. The modes are found in this
way much more easily then by methods of interpolation
from the original frequency-numbers; and the accuracy
is probably quite close enough when one considers the
other sources of error inherent in the general investi-
gation.

Further graphical representation of the results of the
measurements by these integral curves is really the most
convenient method. One does not usually want to know
how many fish in a catch were between, say, 20 and
21 cms. in length, which is all that can easily be read
from the differential curves ; but what percentage of the
whole catch is over, or under certain lengths, say 8 inches,
and this is obtained at once from the graphs. The
percentage of fish caught by a six-inch trawl mesh, at a
certain time of the year, and on a certain fishing ground,
between, say, 8 inches and 10 inches, is obtained by
graphical interpolation, by drawing lines from the axis
of X, parallel to the axis of y, and then, drawing lines
parallel to the axis of x from the points on the curve, and
letting these cut the axis of y. This is usually the sort
of question that arises in practical fishery discussions.

If it is desired to trace the seasonal changes taking
place during a period of two or three months, on a
particular fishing ground, with respect to the size of the
plaice present, the curves for these months can be drawn
to the same axes of coordinates. It is useful in such
cases to change the origin to the point of inflexion, finding
new coordinates by the formulae, x' = x-a, and y’ = y -h,
{a, h) being the coordinates of the point of inflexion.
New scales are then drawn. All the conventions as to
sign then have meanings : positive values of x represent

SEA-FISHERIES LABORATORA^

113

the modal length +a;, and negative values the modal
length - ^ ; and positive values of y represent the modal
frequency + y, while negative values are the modal
frequency — y. I have drawn and discussed several such
diagrams in a later section of the report, and it will be
seen at once that these afford a picture of the changes
taking place on the fishing grounds. Parts of each curve
are, as it were, eaten away, showing how the fish popula-
tion has changed as the result of the operation of several
factors.

Several diagrams are given in section 5 showing
the relation of length and weight in plaice. That on
p. 141 represents the average weight, in relation to mean
length, of plaice caught in Barrow Channel, Eock
Channel and in Beaumaris Bay. Such curves can be
drawn by making use of the length-weight coefficients
tabulated on p. 179: they are the graphs of the function

K73

^ when the suitable values of k have been

100

substituted. The theoretical curve differs hardly at all
from the smoothed curve of actual values represented in

fig. 79.

The construction of the graphs representing the
length-frequencies in Age-Groups I, II and III will be
discussed in a later section.

The probable errors of the modal lengths have not
been calculated. So far a comparison of the results of
the measurements with similar data for other years is not
possible. In any such comparison, due allowance will
have to be made for the probable errors.

3. MODAL SIZES OF PLAICE ON THE FISHING
GROUNDS.

The determination of the modal sizes of the plaice
inhabiting the various fishing grounds has been the prin-

114 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

cipal object of the present investigation. A knowledge
of these sizes is no less important when considering the
question of the migrations of tlie fish than when practical
regulations have to be elaborated. I would point out, in
the meantime, that no attempt can yet be made to inquire
into the causes of the migrations : it is obvious that
investigation of this nature must await fuller knowledge
of the annual hydrographic changes in the water of the
Irish Sea. The data collected in the present lleport do,
however, possess much value when trawling regulations
are being considered, and may be discussed from this
latter point of view. I think the Committee now, for the
first time, possess definite data with regard to the size of
plaice on the various grounds within their jurisdiction.
If such an investigation as the present one had been
carried out at the beginning of the nineties the results
of a comparison of the sizes of fish caught then and now
would have been of the greatest practical value. But the
trawling experiments made in the past, however valuable
they may have been in the circumstances which dictated
them, are too indefinite to be of much use now.

It is therefore most useful that the data of the
present Report should be published in detail, so that the
condition of the fishing grounds during the period 1908-
1910 should be recorded for comparison for future work.
Obviously the “ lumping together ” of the results of the
hauls cannot be practised to a great extent, since one
cannot foresee the purposes for which the figures may be
used. But it would require a great amount of space to
record the results of each haul of the trawl net separately,
and I think that little, if anything, is sacrificed by
combining the results for each month, in each of the
areas. In many cases only one haul is recorded for the
month, but when the figures are large — exceeding 1,000
—they represent from two to five separate hauls.

SEA-FISHERIES LABORATORY.

115

It will be seen that the series of hauls is far from
being complete with regard to each area. This is partly
due to the fact that there are sometimes comparatively
few plaice on the grounds in question; but it is more
often due to difficulty in getting the Fishery Officers to
understand their instructions. This has really been the
most troublesome and discouraging part of the whole
investigation, and one feels that results of value may have
been lost by the failure to obtain an uniform series of
data for each of the fishing grounds.

Only the actual data themselves are tabulated, and
the probable errors of the modes, etc., have not so far
been considered. It is quite clear that separate vseries of
figures representing the observations of several years, or
of several different areas, cannot properly be compared
with each other, unless due regard is paid to the statistical
errors of the values compared. But the necessity for the
calculation of these factors does not yet arise, since no
comparisons are made, except a few which are purely
provisional in their nature. It must, however, be con-
tinually borne in mind, whenever any two curves, or
series of figures, are compared with each other, that every
point on the curve, or figure in the series, is only an
approximation to the (unknown) real value, and is subject
to more or less error. It is always possible to find the
limits of this error, and when one makes a comparison,
the values compared must obviously be greater than the
limits of error.

We may now consider the various fishing grounds in
detail. The figures relating to the Firth of Clyde, Luce
Bay, and the Bahama Bank area, are records of very few
hauls, and are only recorded for comparison with the
Lancashire and Welsh grounds. The Clyde off-shore
from Corsewall Point is a fishing ground characterised by

116 TRANSACTIONS LIVERTOOL BIOLOGICAL SOCIETY.

a much more abundant fish fauna (in the sense of variety
of species) than any part of the Irish Sea. The plaice are
mostly large : thus the smallest caught was 65 cms. in
length, which represents approximately the largest plaice
usually found on most of the Lancasliire fishing grounds.
Luce Bay contains plaice of nearly all sizes, and the fact
that few are recorded in the Tables of less than 15 cm. in
length is due merely to the condition that a 6J-inch mesh
was employed in the trawl net. When a smaller mesh is
used numbers of small plaice may be taken here also.
The plaice population near the banks off the North end
of the Isle of Man is a migrant one, and fish are only
abundant there at the beginning of the year. From
Bahama Bank over to the Selker Light Ship, off the
coast of Cumberland, is a spawning area, and plaice from
Luce Bay, the Solway, and parts of the sea oft' the coasts
of Lancashire and North Wales resort there to spawn.
At other times there are comparatively few fish there;
the bottom is as bare as a billiard ball,” the fishermen
skippers say, a statement wLich is, to a certain extent,
hyperbolical.

Duddon Banks.

The fishing grounds in this area were visited several
times in the spring by Captain Wignall, when getting
material for study in the fishermen’s classes, and plaice
were fairly abundant, the modal sizes show little signifi-
cant variation during the spring months, but it is clear
that the fish were steadily increasing in length. The
percentage at and over 8 inches in length (20’5 cms., say)
varied from 33 to 39. The curve for May can just be
seen to be bi-modal, a condition which indicates change
in the fish population either by immigration, emigration,
or reduction by intensive fishing. In November Captain

SEA-FISHERIES LABORATORY.

117

Wignall again visited this district and made a catch.
The proportion of plaice at and over 8 inches long had

%

Fig. 12. Upper fig. A, lower fig. B. Curves of Percentage of plaice
caught at and above each unit of length.

then risen to 82 per cent, more than in most other catches
recorded in this report. From the appearance of the

118 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

curves I tliink that these plaice had inhabited this area
during the entire summer and autumn, and had been
practically unfished. The hauls for March and November
are grajihed as fig. 12 li.

Barrow Channel.

The sample catches made in this district were mostly
small ones, being made by one of the Bailiff’s sailing
boats, employing a 25-feet trawl. They are, however,
sufficient to indicate the changes taking place. Barrow
Channel is not a nursery,” that is, it is not a shrimping
area characterised by a small-plaice population, and the
flukes that are found there in abundance during the
summer and autumn are an immigrant population. The
family of curves in fig. Id represent the changes
during the first four months of the year, and have been
drawn, as already described, by changing the origin of
co-ordinates in each case, so that it is situated on the
point representing the modal size and frequency. Now, it
will be seen at once from the graphs that the plaice
population is, as it were, being eaten away from one end ;
it is the larger fish that are disappearing during those
months, being caught by the stake nets in this neighbour-
hood, or perhaps migrating outwards towards the
spawning area off the Cumberland coast. May is the
transitional month, and an in-shore migration, or perhaps
a migration from other small-fish areas, begins, so that
from that month till about October plaice are abundant,
and are fairly large fish. But the stock is not being
replenished after the middle of the year, and we find from
then that the fish become less abundant and the larger
sizes are fewer and fewer as the year progresses.

The modal size shows significant variations from
season to season. It is at a minimum — about IT'5 cms. — in

SEA-FISHERIES LABORATORY.

119

the months January to April, and then begins to increase
towards a maximum — about 24‘5 cms. — in July. This

Fig. 13. Percentages of plaice at and above each centimetre of length
caught in Barrow Channel during January- April, 1909.

The construction is explained in the text.

increase in modal length is due simply to the growth of
the fish which have migrated into the Channel, and

120 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

adjoining area, in the spring of the year. After July the
modal size begins to decrease, and this is due to the
fishing-out of the larger plaice.

Considering now the proportion of fish over 8 inches
(a purely arbitrary size which is suggested by the fishery
regulations) we see a change analogous to those indicated
above takes place throughout the year. In January
there were about 25 per cent, of fish in the catch at and
over 8 inches in length, and this proportion steadily fell
to about 10 per cent, in April. Then it rose again as
steadily till July — the month of the greatest modal size—
when over 90 per cent, of the plaice caught were at and
over 8 inches in length. From July the proportion
steadily falls towards the end of the year.

Whether or not a 6-inch mesh should be allowed for
this area does not appear to me to be a question worth
discussing. If the fishermen desire it they may as well
be allowed to use it. When the plaice are abundant the
proportion of the whole catch taken by a 6-inch mesh
which is over 8 inches long is considerable; and con-
versely when the fish are small, so that a 6-inch mesh
will catch a considerable proportion of plaice which are
less than 8 inches in length, the fish are so scarce that the
regulations have no practical importance.

Fleetwood Channel.

This area includes parts of the estuaries of the Eivers
Lune and Wyre. The catches quoted were made by the
same officer and the same gear as in the case of Barrow
Channel. They do not form so complete a series as in
the latter district, but they indicate a somewhat similar
series of changes. The increase in modal size persists
till about September, when the plaice begin to decrease
in abundance. This decrease in abundance is probably

SEA-FISHERIES LABORATORY.

121

due to migration out into deep water during the autumn
and early winter to a greater extent than to fishing-out.
Here again the trawl-mesh may, in my opinion, be either
G inch or 7 inch — the smaller size can hardly be of serious
detriment to the general fisheries.

Only these two parts of the Morecambe Bay area
have been sampled, but obviously the shallow channels
higher up : near Morecambe, for instance, and towards
Ulverston and Grange, on the Northern side, deserve
attention. There are typical small-fish grounds on both
sides — shrimping areas which constitute “ nurseries,” and
a certain amount of trawling by second-class boats is
carried on. There is also a good deal of stake-netting,
and statistics of the sizes of plaice and soles caught would
be desirable. It should be remembered that stake netting
is a very considerable industry in this part of Lancashire
and that large quantities of plaice caught in this manner
are sent to the markets.*

Nelson Buoy Grounds.

There is often a considerable amount of trawling on
the grounds off Nelson Buoy during the summer and
autumn, and the plaice taken are mostly rather small fish.
They do not appear (from the sample hauls recorded) to
have been so abundant in 1909 as in some former years.
The catches quoted in the tables do not show the same
series of changes as in the cases of the Fleetwood and
Barrow Channel grounds. We have to deal here with a
plaice population migrating out from the nurseries in the
estuary of the Ilibble and inhabiting for some months the
grounds lying between the Morecambe Bay and the
Liverpool North-West Lightships and the Nelson Buoy.
This plaice population becomes reduced during the

* A. Scott, \%th Quarterly Rept, Scientific W ork, Lancashire Sea-
Fish. Committee, Oct., 1909, p. 10.

122 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY-

autumn (1) by fishing-out, (2) by the migration into
deeper waters off-shore to the South and West of the
larger fish, and (3) by an along-shore migration of the
smaller fish during the autumn and early winter. It will
be seen that we have a bi-modal curve during March (as
in the case of Barrow Channel and Fleetwood Channel in
January and February), indicating extensive changes in
the plaice population. Thereafter the modal sizes show
little or no significant change, though perhaps there is a
slight increase due to the growth of the fish. The
frequencies also show little significant change; the pro-
portion of fish at and over 8 inches in length varies from
about 30 per cent, to TO per cent., being greatest in July.
The statistics are not, however, extensive enough to enable
one to discuss this point further.

Fishing Grounds off the Estuaries of the Mersey and Dee.

These grounds are the most interesting of the
Lancashire and Western Sea Fisheries area, since it is
here that we find the “ fish-nursery in its most typical
form. Fortunately we have a fairly complete series of
statistics, thanks to the conscientious work of Captain
Eccles, the Bailiff in charge of the sub-district. I do
not mean to say that the information is all that is
desirable, but the data at our disposal are very instructive.
The Mersey area is really one of the most diversified in
the whole Irish Sea, that is from the point of view of its
fisheries. It includes large tracts of shallow water, on
the margins of the channels and banks, suitable in every
respect for the nurture of young fishes. These shallow
waters form a very productive shrimping area. There is
comparatively deep water (from the in-shore fishery point
of view) in the outer channels; and there are “rough”
bottoms, some of which are prawning areas and exhibit

SEA-FISHERIES LABORATORY.

123

the typical varied Laminarian zone invertebrate and fish
faunas, in Rock Channel, in the Dee, and off Air Point.
The in-shore parts of Liverpool Bay are probably the
scene of hydrographic changes to an extent greater than
any other corresponding area in the Irish Sea, and it is
probable that to these changes may be attributed such
remarkable instances of fish migrations on the large scale
as the exceptional abundance of herrings in the early
nineties, and the extensive immigration of haddocks in
the same decade.

°lo

Fig. 14. Percentages of plaice at and over each unit of length, in the
catches made in the Mersey area by trawl nets of various sizes of mesh.

(1) The Shrimp-trawl Catche s. — These
were made by a 25 feet trawl net of ^ inch mesh. The
numbers are fairly large, and the tables may be
regarded as affording a very reliable picture of the size
of ihe small plaice inhabiting the nursery grounds. It
will be seen that there is little or no significant difference.

124 TKANSACTJONS LIVEKTOOL BlOT.OGICAli SOCIETY.

from month to month, in the modal size of the small
plaice taken in the shrimp trawl : this varies from about
7 to cms., with corresponding values of frequency of
about GO per cent, to 70 per cent. That is the proportion
of the whole catch which is at and over the mean modal
length ( = about 7'3 cms.) is about 67 per cent. At the
beginning and end of the year the curves are apparently
simple, but at most other times there are two modes, the

lo

lesser being due to immigration of larger fish at the
beginning of the year, and to the growth of the small
fish at the latter end of the year. The mean proportion
of the total catch which consists of plaice between 5 and
9 cms. in length is very nearly 66 per cent. That is to
say, a shrimp trawl-net of 25 feet beam and | inch mesh
catches a certain number of young plaice,* and about

* Average values for the numbers of small plaice taken are given
by Dr. Jenkins and myself in Ann. Eept. Lancashire Sea-Fish. Lahy.
for 1900, p. 39, 1901.

SEA-FISHERIES LABORATORY.

125

two-thirds of these are from 2 to 3| inches in
length.

(2) The 6-inch trawl-mesh catche s —
Rock Channe 1. — Except for the end of the year,
when the catches were rather small, plaice being scarce
in Rock Channel, the figures recorded in the tables afford
reliable pictures of the kind of fish inhabiting this part
of the district. It will be seen that we have to deal here
with a typical “ small-fish population. The modal sizes
vary between 16^ and 19 centimetres, differences which
do not appear to me to be of significance. At the middle
of the year (June) the modal size is least and the
frequency curve shows two maxima. This bi-modal
distribution is due to the growth of the plaice ; about
this time vast quantities of the smaller fish previously
less than about 10 cms. in length have grown to be large
enough to be caught in numbers in the 6-inch mesh trawl
net. These little fish decrease the modal size and swamp
the large plaice, producing the bi-modal curve. Before
this time the predominant fish population represented in
the catches were those of both of the two previous years’
spawning; after June the predominant part of the catch
consists of fish of the previous year’s spawning.

Considering the plaice which are 8 inches long and
less than 8 inches long, we find that from March to July
the proportion of the whole catch consisting of fish below
this length varied from 80 per cent, to 87 per cent. In
June there are about 93 per cent, of plaice less than
8 inches long in the catch. After the end of June the
percentage falls. In September 69 per cent, were less
than 8 inches in length, in October 78 per cent., in
November 50 per cent., and in December 40 per cent.
But the catches during the latter two months were small
ones. When these figures come to be compared with

126 TRANSACTIONS lilVERTOOL BIOLOGICAL SOCIETY.

those of future years, it will be necessary to pay due
regard to the probable errors, but in the meantime we
may say that of all the plaice caught by a 6-inch trawl-
net in Eock Channel, about 64 per cent, were less than
8 inches long.

Six-inch trawl-mesh catches : Near
M e r s e y B a r. — There are few of such catches recorded,
but it wdll be seen at once by a glance at the tables that
a rather different class of plaice are taken in this part
of the Mersey area. The modal lengths vary from about
18 to 21 cms. Eoughly speaking, we may say that the
modal length is about 8 inches. Then about 46 per
cent, of the plaice are less than 8 inches long, as compared
with about 64 per cent, in the Eock Channel area. But
the dispersion of the sizes in the Bar catches is much
greater than in the catches made in the former area, and
quite a fair proportion of medium-sized fish are taken.

Six-inch catches: Horse Channe 1.--
Sample catches were made in this area during the months
June to November inclusive, and the numbers of fish
taken are large enough to enable us to form a reliable
opinion as to the effect of this means of capture. The
modal lengths vary from IS'S to 21*5 cms., and are
significantly greater than in the Eock Channel ground.
The curves are in all cases bi-modal ones, and, as in the
case of the catches made near the Mersey Bar the
dispersion is much greater than that exhibited by the
catches in the small-fish area. The proportion of plaice
less than 8 inches long in the catch is about two-thirds
in June, and falls to about one-quarter in September.
Then, as the result of fishing-out, perhaps also of emigra-
tion into deeper water, the proportion of fish under
8 inches in length rises, and is about 40 per cent, in
November.

SEA-FISHERIES LABORATORY.

127

It will be seen tliat there is a notable difference
between the sizes of plaice taken in the 6-inch trawl net
when worked in Rock Channel and the closely adjacent
shallow waters, and in the deeper water in the outer
channels. In the former area the 6-inch trawl mesh
undoubtedly catches a fairly large proportion of small
plaice of comparatively little marketable value. In the
deeper water off-shore this proportion of small plaice is
much less, and may be neglected. I see no reason why
a 6-inch trawl-mesh should not be regarded as a reason-
able instrument of capture. It may be urged that it is
a destructive engine in shallow waters such as those in
the Rock Channel ; but I do not think we have evidence
enough to justify us in preventing its use if the fishermen
should strongly desire it. I will, however, return to this
])oint later on.

The Beaumaris and Red Wharf Bay Area.

The fishing grounds West from the estuary of the
Dee are characterised b}^ a plaice population in which the
fish are considerably larger than in the shallow waters
off the coasts of Lancashire and Cheshire. The fishery
on these grounds is an autumn or early winter one.
Sometimes the bulk of the plaice are taken near Colwyn
Bay, as during the winter before last ; but in other years
large quantities of plaice are taken in Red Wharf and
Beaumaris Bays. In the later months of 1907 and the
beginning of 1908 there was a very profitable plaice
fishery in Red Wharf Bay. At the end of 1908 the fish
were most abundant, and were largest, off Colwyn; and
at the end of 1909 the biggest catches, and the largest
plaice, were obtained from the fishery grounds immedi-
ately round Grreat Orme’s Head and in Beaumaris Bay.
At the very end of the year large plaice began to be

i

T‘2S THAXSACTIONS LIVERPOOL B10T.0(i K'AT. SOCIE'I’Y.

plontifiil in Red Wharf ]hay. The?;e rliangos are, no
doubt, to be assoeiated with variations in the hydro-
"Tapliic conditions of the sea in these regions, but just
what is the nature of these associations is as vet doubtful.

Fairly large catches of plaice were made in the
Beaumaris and Bed Wharf area by Captain Wignall
during the autumn of 1909, and the figures appear to me
to be very reliable and to give us a very accurate picture
of the distribution of sizes on this fishing ground. I
liave grouped together all the catches made in “ Beau-
maris Bay,” “ Conway Bay,” ‘‘ Off Orme’s Head,” and
in “ Colwyn Bay.” All these grounds may be regarded,
during this last fishing season at least, as constituting
practically the same area. The catches made in Bed
Wharf Bay have, ho-wever, been kept separate from the
rest, though it would not have made much difference to
the results had they been incorporated with the rest.

It will be seen from the tables and from the curves
in fig. 12 that the plaice taken were smallest in June
and July, and that they become larger as the end of the
year approaches. The curves are uni-modal in June and
July, the mode being about 20 cms. After August the
dispersion increases and the fish become, on the whole,
larger. From September to the end of the year the
curves are bi-modal. Those for November are remarkably
similar, and the October and November curves can be
superposed, so alike are they in magnitude and phase.
This similarity appears to me to indicate that we are
dealing here with samples which are of great reliability.
In December the modal sizes are greater than in the
preceding months. The double mode indicates the
presence of plaice of Age-Groups II and III, though, of
course, the positions of the modes are not exactly those of
the maximal sizes in those groups. Plaice up to six years

S E A - I S 1 1 E K 1 ]<: S L A H K A T O U Y .

129

of age were represented in these catches, though not.
abundantly, and the older dsh were not numerous enough
to affect the form of the curves.

The difference between these plaice and those taken
off the coasts of Lancashire and Cheshire is best seen
when we compare the proportion of the whole catch
consisting of fish less than 8 inches long. In June and
July about 46 per cent, of the catches made in Beaumaris
Bay were plaice less than 8 inches long. The corre-
sponding percentage for Bed Wharf Bay in July was 44.
But on both grounds from August onw^ards the proportion
of fish less than 8 inches long drops to about 25, and in
some cases was less than 20.

Obviously the question of the restriction of the mesh
has little interest in relation to these grounds. The
proportion of small plaice taken by the 6-inch trawl-mesh
in those months when the fish are abundant is so small
that we cannot conclude that the general use of this net
can do any harm to the fishery, and if the fishermen wish
to employ it in these in-shore waters I see no reason why
they should not be allowed to do so.

Catches made in Cardigan Bay.

Comparatively few sample catches have been made in
Carnarvon and Cardigan Bays, and I quote only those
taken from the trawling grounds off ~New Quay Head,
in Cardigan Bay. We have to deal here with fairly large
plaice; thus the modal sizes vary from 29 cms. in
February to 21 in May. Obviously a migration of
smaller fish was taking place about the end of this
period; thus the modal size is decreasing all the time,
and it is evident, from a consideration of the curves for
March, April and May that this is due to the swamping
effect on the large fish population, of a host of immigrant

180 TKANSAC riONS LI VEK [’OOI. IMOI.OGICAL SOCreTV.

smaller plaice, and not to Hsbing-out. In February only
2 per cent, of the fish were under 8 inches in length, in
March 6 per cent., in April 17 per cent., and in May
as much as 21 per cent. Apparently the conditions at
the south end of Cardigan Bay are very different from
those off the coast of Lancashire. The natural conditions
are no doubt not the same, but much of the difference
may be due simply to the fact that the fishery at this
imrt of the coast is very much less intense than in the
highly exploited grounds to the North. The distribution
of ])laice in Cardigan and Carnarvon Bays would be well
worth closer attention than we have been able to give to
it.

L AGE-GROUPS.

The determination of the modal lengths of the plaice
inhabiting the various fishing grounds in the Lancashire
district has been the most unsatisfactory part of the whole
investigation. The total number of fish examined is a
little over 2,500, probably much too small a number. If
these fish had all been collected from one fishing ground,
and during the same time of year, reliable figures for the
lengths of plaice one, two and three years of age might
have been obtained. In the Report on this Avork,
published in 1909, I gave particulars relating to the
examination of about 1,000 plaice caught during the year
in the northern part of the district ; and it was seen, on
considering these figures that the process of “lumping”
the fish caught, even on grounds Avhich are not far distant
from each other, led to erroneous conclusions. Far more
faulty, however, was the method of combining the results
of examinations of fish caught at different times in the
year ; for while the curve of growth of the fish is a

* Lancashire Sea Fisheries Report for 1908, p. 83, 1909.

SEA-FISHEKIES LABOEATOEY.

131

continuous one, that representing the age is discontinuous.
It is sometimes difficult, at particular seasons in the year,
to be sure of the number of rings of growth in the
otolith. A faint marking on the margin may be the
beginning of another opaque ring, but the appearance
may also be only the effect of refraction. A week or so later
it might have been possible to ascertain wdth certainty
the age of the otolith in question ; but there would be a
difference of a whole year in the recorded age of the fish,
while the length of the latter would hardly have changed.
Obviously the “ lumping together of catches consisting
of plaice which were passing through this transition
stage, and others taken before or after* the cessation of
growth, would produce discordant results.

The plaice examined in 1909 are therefore grouped
according to the precise fishing ground and the month of
capture. The disadvantage inherent in this classification
of the results is that small numbers of fish must, of
necessity, be considered. It would, of course, be possible
to examine, say, 1,000 plaice from each fishing ground
during three or four sample months of the year, but the
practical difficulties of investigation on such a scale are
very obvious. On the whole it is better to deal with
small numbers of fish taken under precisely similar
conditions, and trust that the summation of the results
of several years’ investigation may afford accurate data
for age-determinations.

The tables on pp. 172-178 include the results of all
the measurements made in 1909, and are summarised in
the table on p. 180. It will be seen, by inspection

of the latter, that there are gaps in the series representing
each fishing-ground ; and these gaps are due partly to
the fact that plaice are not present on each ground to
abundance throughout the year, and partly to the not

132 TRANSACTIONS LIVERPOOL lUOLOGICAL SOCIETY.

luimitural reluctance ol‘ the Fishery Officers to mis-
apprehend their instructions that large samples of the
hsh caught by them should be sent to the laboratories
periodically. The modal lengths tabulated on p. 138 have
been determined by integration of the original frequency
series, as in the case of the other tables. As a rule there
is little difficulty in estimating very approximately the
position of the modal frequency. AVhen the curves are
drawn it is often apparent that one or other of the
extremities is unrepresented in the series, but this may
affect very little the value of the mode. As a rule, when
30 to 50 fish of any of the Age-Clroups are examined,
the mode can be ascertained. It is sometimes impossible
to determine the modal length of Groups I and II in the
same catch, the latter consisting predominantly of fish
of the same year; and as a rule it is impossible to
ascertain the length of plaice of Age-Group III except in
one or two of the Lancashire fishing grounds. Plaice of
more than three years of age are not allowed to inhabit
the shallow waters off the coasts of Lancashire and Aorth
Wales in very great numbers.

It would be a result of very great value if one could
determine the law of variation in growth, so that a
theoretical frequency-curve could be substituted for the
observed distribution. Unfortunately this has not been
possible. In order to determine the equation of the curve
which the observations would fit with least improbability,
a very large number of plaice would have to be examined,
and one would have to collect the fish under conditions
which would ensure the homogenity of the material ; that
is, they must be caught at the same time of year, and on
the same place, so as to avoid the influence produced by
migrations; and the catches would have to be made by
means of trawl nets of dift'erent meshes. For just as no

SEA-FISHERIES LABORATORY.

133

single plankton net can be expected to collect a represen-
tative sample, so no one trawl-mesh gives ns a representa-
tive catch of the fish resident on the sea-bottom.

Three groups of plaice caught during 1909 have been
examined statistically in order to see whether the
distribution of the length followed the normal law. The
results of these examinations are given in Tables on
pp. 181-182, and the curves (figs. 10 and 18) express the
distribution graphically. It will be seen that the
correspondence is in no case a close one, and that it is
probable that the distribution would be better repre-
sented by a skew curve.

Fig. 16. Catch of 44 plaice from Barrow Channel, 12 July, 1909, Gp. II $ •
Correspondence with curve of error.

1 thought it might be possible to decide whether or
not the deviations from the modal length in a number of
young plaice, of very approximately the same age, were
distributed according to the normal law of error. Tor
this purpose a number of measurements made by Mr.
H. C. Chadwick were available."^ The fish had been

deferred to in Annual Report of Liverpool ^Marine Biology
Committee for 1907, p, 18.

184 TKANSACTIONS LIVEIU'OOL EiOLOGlCAL SOCIETY.

spawned in the large pond at Uie Port Erin Hatchery
about the 2bth of April, 1906; probably the error in this

Fig. 17. Catch of 95 plaice from near Nelson Buoy, June, 1909. Gp. II S •
Correspondence with curve of error.

Fig. 18. Catch of 99 plaice from near Nelson Buoy, June, 1909. Gp. II $ .
Correspondence with curve of error.

date does not exceed + 14 days. The eggs collected from
the pond were, as a rule, put in the incubating boxes, but

SEA-FlSllElUEb LAEOKATORY.

135

a large number bad been put into a division of the pond,
where they developed until the close of the spawning
season of the following year. During the winter of 1906
the whole pond had been emptied, cleaned out, and the
bottom was allowed to dry. It is, therefore, impossible
that any small plaice were there at the beginning of the
hatching season of 1906, and we may be confident that the
hsh measured in May, 1907, were just over one year old.

The sizes of the 200 plaice examined are tabulated
on p. 183. They were measured to the nearest ^ inch,
and the figures are grouped into J inch classes. The
mode is at 2*625 inches, a result which agrees well with
what we know of the life-history of the plaice in the sea,
and the limits of variation are also concordant with such
impressions as I have received on looking over the
contents of the catches made by shrimp trawls worked
on shrimping areas when small plaice are abundant. It
will be seen from the table on p. 163, representing the
results of shrimp-net hauls in the Mersey, that the
highest percentage of small plaice caught is that about
6*5 centimetres (approximately 2'6 inches). I do not
know what these small plaice fed upon in the spawning
pond, but the latter was said to contain a very abundant
copepod fauna, and on the Mersey grounds copepods form
the diet of small plaice up to about 1 inch in length.

It is evident from a glance at the series of measure-
ments on p. 183 that the sizes of these 200 young plaice
cannot be arranged in a simple frequency curve. At
about 4 inches the numbers of hsh in each class begin to
increase. It is true that this increase is small, and the
total instances are not enough to enable one to be sure
as to its meaning. It is, however, quite possible that we
are really dealing with heterogeneous data. The spawning
pond was stocked with plaice collected (I) from Port Erin

136 TKANSACTlUiS'S LlVKRl’UUL HlULUGlCAL 8(K’1KTV.

Bay, and (2) from Luce Bay. ?sow the latter area is
strictly preserved against trawling, while the sea round
the Isle of Man is certainly fished tor all it is worth.
Further, tliere is a very abundant plaice population in
Luce Bay, while that round the South end of tJie Isle of
Mail is very sparse. It is, therefore, quite possible that the
lo(ail plaice were different from those of Luce Bay, and
had a more rapid rate of growth than the fish of the
latter region. This ditf'erence in the spawning fish would
result in a difference of rate of growth in the lai vae and
young fish. The double mode, in fact, may be taken to
indicate two strains of fish.

On the other hand, it may simply indicate that the
rale of growth of the plaice is such that the deviations
from the modal character tor a homogeneous group form
a skew curve. It is not possible to settle this point in
the meantime. I have, however, attempted to make a
correspondence between the deviations exhibited by the
Port Erin plaice and the normal curve of frequency error.
Taking the mode at 2 025 inches, the part of the series
as far above the mode, as the smallest fish is below it, is
neglected. The standard deviation and modulus have,
however, been calculated for the entire series; but in
constructing the algebraic curve the modulus has been
taken as 0'8 instead of the calculated value, 0‘712.
Points on the normal curve are then found by a method
suggested by Mr. A. L. Bowley.''" The correspondence
is not good, and though it is not quite justifiable to con-
clude that the observed measurements are those that would
result, with least improbability, from the normal curve,
it seems to me that the distribution is almost as likely
to follow the latter law, as that expressed by the equation
of one of the asymmetrical frequency curves. The

- Tllisj differs slightly from that indicated in Mr. Bowley's Elements
of Statistics.

S E A-E 1 S IlEK lES LABOR AT( )R V .

137

symmetrical curve would not, strictly speaking, be the
normal curve of error, deduced from the binomial
expansion, with branches extending to infinity in either
direction, but rather Pearson's ‘‘ Type II,’’ that is.

which is symmetrical, but limited in both directiojis.

Leaving for further investigation the question of the
a])plication of a theoretical frequency-curve, we may
consider the modal sizes of plaice of Age-Groups I, II,
and III, inhabiting the coasts of Lancashire and North
Wales. It is quite impracticable to attempt to estimate
the ages of fish older than these, for such plaice are so
sparingly represented on the in-shore fishing grounds as
to make any such estimate subject to considerable error.
During the autumn there is indeed an immigration of
large mature plaice into shallow water, so that fish
belonging to Age-Groups lY and Y may be taken in
Barrow Channel and off the coasts of the North Welsh
counties, but the number of such plaice examined is far
too small to be capable of statistical treatment. It will
also be seen from the tables that fairly large plaice may
be taken on the banks off the North of the Isle of Man,
in the Firth of Clyde and in Luce Bay, and the results
of several hauls on these grounds are given for tire
purpose of comparison with the Lancashire fishing area.

The plaice caught on the latter grounds belong almost
entirely to Age-Groups 0, I and II. Barrow ChanneJ,
the shallow water in the estuaries of the Rivers Lune and
Y"yre, the grounds off Nelson Buoy, and the Rock
Channel in the Mersey area may be taken to represent
the Lancashire iu-shore area, and there is comparatively
little difference in the modal sizes of the plaice captured
on these grounds. The table on p. 180 may be very
briefly summarised as follows: —

138 TKANSACTIONS LIVEIU’OOL JUOEOGICAL SOCIETY.

Group I. Modal lengths in the s j) r i n g
in 0 11 t li s (•laniiary-^larcli).

(1) Harrow Channel :

Males, 18 cms. long; females, 18 cms. long.

(2) Lnne and W3^re :

Males, IT cms. long; females, IT cms. long.

(3) Hock Channel :

Males, IT’5 cms. long; females, 18 cms. long.

,, Modal lengths in the autumn

months (September to November).

(1) Barrow Channel :

Males, 19 cms. long; females, 19 cms. long.

(2) Lune and Wyre :

Males, 18 cms. long; females, 18*5 cms. long.

(3) Bock Channel :

Males, 19 cms. long; females, 19 cms. long.

Group II. Modal lengths in the spring
months.

(1) Barrow Channel :

Males, 23 cms. long; females, 23 cms. long.

(2) Lune and Wyre:

Males, 18'5 cms. long; females, 21 cms. long.

(3) Bock Channel: —

Males, 21 cms. long; females, 21-5 cms. long.

Modal lengths in the autumn
months.

(1) Barrow Channel :

Males, 22 cms. long; females, 22 cms. long.

(2) Lune and Wyre :

Males, 24 cms. long; females, 22 cms. long.

(3) Bock Channel :

Maks, 21 cms. long; females, 21*5 cms. long.

The diherences in the modal lengths of plaice taken
from these various grounds are very slight, and may be
expected to be less than the probable errors of the deter-

SEA-FISHERIES LABORATORY.

139

ulinatioiis. It is to he noted that tliere are no marked
differences between the lengths of the males and females
of each Group : what differences there are are often
reversed. It is also to be noted that the differences
between the modal lengths of Age-Groups I and II
are very slight, amounting to only 3 to 4 cms. I expected
that the average growth during the third year of life
would have been greater than is indicated by the above
figures.

Quite a different plaice population is contained on
the grounds off Hhyl, round Great Orme’s Head, and in
Eed Wharf Bay. Here the fish belonging to Age-
Group I are far less in proportion to the older fish than
on the Lancashire fishing grounds. So few fish of this
group were contained in the sample sent to me that I
liave not attempted to estimate their modal lengths ; the
figures are, however, given in detail in the tables. On
the other hand, Age-Group III is represented in sufficient
numbers to enable the modal lengths to be determined.

Age-Group II. Beaumaris Bay and adjacent

grounds.

Tidy: Males, 19’5 cms. long; females 20 cms. long.

Nov.-Dee. : Males, 23 cms. long; females, 23 cms. long.

Age-Group III. Beaumaris Bay and adjacent

grounds.

Nov.-Dee.: Males 27 cms. long; females, 29 cms. long.

5. LENGTH AND WEIGHT.

The object of determining the weight of the plaice
taken on the various fishing grounds was to find a
numerical expression for the “ condition ” of the fish,
both with regard to season and fishing ground. One
knows very well when a plaice is “in condition” from

140 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

its general appearance, bni il is obviously desirable io
have some measures of this qua lily, in order that it may
be accurately compared in different samples. The samples
received represent most of the fishing districts, but fairly
srood series were obtained only from the Harrow Channel

o

and the Mersey shallow water grounds.

As a rule the method of weighing was to sort out the
fish in each sample into centimetre groups, and then to
take the total weight of all the fish in each group. Some-
times each fish was weighed separately. The weight was
always found to the nearest gramme, whether in a single
fish or a number. Mature females with ripening ovaries
Tvere weighed, but the results were not made use of in
determining averages. The tables apply, therefore, to
immature females or to mature and immature males.

The average weights themselves are not published ;
obviously to do so would involve much space, and the
table of values of the coefficient k can be used to find the
average weight of the plaice of each fishing ground and

season represented. The weight = h, I and the

weight being taken in centimetres and grammes respec-
tively. Since the h of the table is itself an average
number, the weight will represent the mean for the place
and time in consideration.

Fig. 19 represents the increase of weight wdth
length in the case of four typical catches of plaice. That
from Barrow Channel in July may be regarded as repre-
senting plaice in good condition ; while the catch for
February represents the fish when in the worst condition
of the year. One sees that the differences are fairly
considerable : a 10-inch plaice in good condition weighs
about 6f ounces, while a fish of the same length taken at
the time of its worst condition weighs only 5^ ounces.
These July fish were in first-rate condition and were

SEA- FISHERIES LABORATORY.

11]

mostly feeding on small mussels, about | to inch long.
The catch from Beaumaris Bay in September consisted of

fish nearly as good, but of all the plaice sampled, those
from Barrow Channel in J uly were the best. The February

142

TRANSACTIONS LIVERPOOL lUOLOGlCAL SOCIETY.

catch from Hock (.4iaiincl represents ih(^ poorest plaice
taken in the Lancashirt^ and Welsh 4istrict, with the
exception of one catch from Menai Straits in March — a
10-inch fisli from the Hock Channel catch weighed only
about 44 ounces.

/,■ p

The figure is not the graph of the function

but each of the curves is a smooth line drawn as near as
possible to the points representing the actual average
weights. It is not drawn absolutely correctly and is
intended to show the relative weights at different places;
closer approximations can be made to the weights by
calculating from the table of values of the coefficient h.
Heally true values are not really obtained either by this
process or from a graph on which weights calculated from
the formula are plotted, because the “ constant ” h is not
absolutely a constant, but often varies slightly in the same
series. If it is calculated for each centimetre group in the
same catch it is frequently found that it is greater in
relation to the larger fish than the smaller ones. That is,
the plaice does not grow equally in all dimensions, and
the ratio of length to thickness or average width probably
varies with increasing age.

The values of the coefficient h for three of the series
are plotted in fig. 20. It will be seen that they form
curves with one maximum, which in the case of the two
Channels is in July. The curves probably rise to the
maximum more steeply than they fall to the minimum,
but the number of observations is not great enough to
enable us to be quite sure of this. The minimum appears
to be in January. About the end of November plaice
cease to feed as a rule, and very little is found in their
stomachs until the end of January. In the case of the plaice
taken in Beaumaris and Eed Wharf Bays there appears to
be a notable difference in that the condition of the fish is

SEA-FISllEKlES LABORATORY.

143

maintained till a later period of the year than in the
other two fishing* grounds.

I would direct particular attention to the differences
between the condition of the plaice from these three areas.
I think one can hardly regard these differences as
indicative of different ‘‘ varieties or “ races ” of plaice
in the way one would so interpret structural differences.
The grade of condition appears to depend on the amount
and nature of the food at the disposal of the fish on their
feeding grounds, and on the density of population on
these areas. But it is rather difficult to believe that the
condition depends entirely on the amount of available

Fig. 20. Monthly variations in the value of the coefficient k.

food. I examined the alimentary canals of a number of
plaice caught both in Barrow Channel and in Eock
Channel during the last two years. As a rule the plaice
in the former area contained small mussels from one-
quarter to half-an-inch in length ; while plaice from the
latter area usually contained small cockles, Tellina,
ScrohiculaTia, I)o7iax, and PectinciTia, the latter animal
being very abundant at times. Food molluscs seemed to
be abundant in both areas. Nevertheless, one is forced
to conclude that the fish in Eock Channel are not so well
nourished as those in the northern area ; it mav be

E

144 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

because food is less abundant, or that small mussels form
a more nutritive diet tban tbe other animals mentioned.
The latter conclusion appears reasonable, since the shells
of such small, rapidly growing mussels as were found in
the Barrow Channel plaice were, as a rule, exceedingly
thin. However this may be, there can be no doubt that
we have to deal, in the Eock Channel area, with small
plaice which are below the normal in condition.

The graphs of the variation in value of the coefficient
k, which we may regard as a good index of the condition
of a plaice with regard to nutrition, appear to back up
this conclusion. All through the year the coefficient is
less, in the case of the Eock Channel plaice, than in
plaice either from Barrow Channel or from Beaumaris
and Eed Wharf Bays; and in July the. maximum is
attained in the two former areas, but it is much greater
in the northern than in the southern area. The conclusion
that the Eock Channel plaice are below the normal with
regard to condition appears to be so important that it is
desirable to examine critically the data on which it is
based. The values of the coefficient h represent variations
in the condition of the fish ; when the average weight
(the condition of plaice of a certain length is
relatively high, k is also relatively high, and vice versa.
Each value of k in the table on page 179 is deduced from
weighings of a sample of fish varying from 40 to 150 in
number. Altogether about 1,100 plaice from Eock
Channel and about 740 from Barrow Channel, were
weighed. When there are several determinations of k for
one month, the average is taken. The values of k found
in the table have been smoothed, and the graphs in
fig. 20 represent the monthly variation of these
smoothed numbers. The arithmetic average of the value
of k, for Barrow Channel plaice, for the ten months.

SEA-FISHERIES LABORATORY.

145

January to October, 1909, is 1-034. Tbe similar average
for Eock Cbannel plaice for tbe same months is 0'966.
The former fish are therefore in better condition, since
the average value of ^ is greatest.

Now these mean values are deduced from samples;
obviously the latter must be unreliable to some extent,
since we can never sample an assemblage of organisms
in the sea without error; and it is necessary to ascertain
the limits of error whenever a comparison of two o^ more
series of samples is made. The precision of the mean
depends on the extent to which the data averaged
“ scatter ” from the maximum point in the series, and is
deduced from the standard deviation. The arithmetic
mean (or average) in the case of the Barrow Channel

series is 1'034, and the standard deviation a,

moments” about the mean, and iV=10, the number of
observations. The probable error of the mean is —2^
and IS 0*025.

“ Unless a result exceeds the expected by two or three
times the probable error, it is not safe to assume that the
particular case differs from the expected result.” Now
the mean value of h in the Eock Channel statistics is
0-966, and differs from the mean of the Barrow Channel
statistics by 0’068. The difference is therefore 2*6 times
the value of the probable error, and we are justified in
regarding it as significant, and indicative of a real
difference in the condition of the two fish populations
sampled.

If a complete series of weight statistics for the plaice
of the Beaumaris — Eed Wharf grounds were available,
we should probably find a corresponding significant differ-

being the sum of the “second

146 TRANSACTIONS LIVEKCOOL BIOLOGICAL SOCIETY.

ence. But there are no figures for months prior to July.
The part of the curve drawn does, however, indicate thal
the plaice population differs from that of the other two
areas. We know that the fishery in this part iff the
district is an autumn and winter one, the fish immigrat-
ing into the in-shore waters off the North Welsh coast
late in the year. The fish do not appear ever to have
been in as good condition as those in Barrow Channel
during July, but they retain a high average weight until
late on in the year, when the condition of both Barrow
Channel and Bock Channel has fallen below the mean.

6. INFLUENCE OF SIZE OF MESH.

We should be able to find out what range of sizes of
fish would be caught in trawl-nets of different sizes of
mesh, by making a sufficient number of trial hauls; and
this kind of information is so important, practically, that
it is rather surprising that it has not been obtained long
before the present time. A number of such comparative
hauls were made in the earlier years of the Committee’s
work, but I think the results are far too indefinite and
inexact to be of much use. It is quite absurd to describe
a catch of fish as consisting of so many over, say, 8 inches
in length and so many under 8 inches, for one cannot
say how far below or above the standard size the fish
were. It is only by measuring each fish taken, and then
exercising some care in the calculation of probable
average or modal sizes, that results capable of standing
criticism can be obtained. I do not think that very good
results can be obtained from the use of a double net, a
net of 4-inch mesh, say, outside one of, say, 7-inch mesh.
Obviously the wide meshed net would not make the same
catch as if it were used alone, for the draught of water
through it would be diminished by the small-meshed net

SEA-FISHERIES LABORATORY.

147

outside. We can ascertain the range of sizes of fish
caught in nets of particular mesh only by using each by
itself.

Very few hauls by nets of mesh other than 6 inches
have been made; -they are all recorded in the tables on
pp. 163-165. Captain Eccles used nets of ^-inch mesh
(p. 163), 4-inch mesh (p. 164), 6-inch mesh and 7-inch
mesh (p. 165). The results are rather few yet for
statistical treatment, and one must remember that the
range of sizes of plaice taken in the nets will be affected
by various factors. Thus an unusually large proportion
of invertebrates, say large jelly-fishes or star-fishes, in
the catch will be associated with a larger proportion of
smaller fish ; while a difference in the speed at which the
net is dragged must also affect the catch. I do not
suppose that a 4-inch net dragged from a steamer would
give the same range of sizes as the same net dragged over
the same ground by a sailing boat. Probably two fisher-
men working the same boat and net over the same ground
would not get similar catches. In order to obtain reliable
measures for the catching powers, with regard to the size
of fish, of trawl nets of different meshes it would be
necessary to make a large number of trials on the same
ground and by the same boat and fishermen. I should
think that a dozen hauls by nets of 6 and 7 inch mesh
during the same month, on a ground where fish were
abundant during the whole period, and arranged so that
so many comparison hauls were made on alternate days,
would give fairly reliable results. Of course it might
be objected that the fish population had changed during
the interval, and that it would be difficult to trawl over
precisely the same ground each time, but these objections
appear to me to be cavilling rather than real criticism.
At any rate, no other practicable means of investigation
can be suggested.

148 TRANSACTIONS LIVERPOOL BIOLOGICAL S0CIET\ .

Fig. 14 represents the catches made by four
different trawl nets — a shrimp net of ^-inch mesh, and
three fish trawls. They were all made by Captain Eccles
from a second-class fishing boat in the Horse Channel
area during September; the actual counts of the hsh
taken are given on pp. 159-165. The shrimp net was
used once and caught 579 plaice; the other nets were
used several times each and caught over 1,000 plaice
each. When the figure was first drawn one of the 6-inch
net hauls was omitted, but on replotting the total catch
it was seen that the curve was not materially altered. I
do not propose to deduce any “ factor ” for the catching
power of each net, but quote the results as those obtained
by a thoroughly experienced fisherman in certain
particular cases. The shrimp net, it will be seen, caught
comparatively few fish over 5 inches long. Considering
plaice of 8 inches in length, the figure shows that
about 38 per cent, of the catch of the 4-inch net were of
this length and over it; 70 per cent, of the catch of the
6-inch net were 8 inches and over; and 84 per cent, of
the catch of the 7-inch net were at and over 8 inches.

The 6-inch Trawl-Mesh and Regulations

It has been maintained that the universal employ-
ment of a trawl-net of 6-inch mesh in shallow waters
is likely to be detrimental to the fisheries in general. I
do not think that this is likely to be the case with regard
to plaice — at least the figures compiled in this Report
do not seem to me to support the above contention.
Obviously a narrow-meshed net is likely to be destructive
only in the shallow waters, and at those times in the year
when small plaice are so numerous as to form a large
proportion of all the fish on the ground. On grounds
such as those oh Colwyn, oh Great Orme’s Head, and in
Red Wharf Bay a 6-inch trawl-net is not, in my opinion,
a wastefully destructive instrument of capture. Even

SEA-FISHERIES LABORATORY.

149

in the in-shore waters of Barrow Channel, I do not regard
the destruction of small plaice by the 6-inch net as waste-
ful. It is only in such an area as that in Bock Channel
that the 6-inch trawl appears to have taken an undesirable
proportion of plaice of lengths less than 8 inches.

But there is evidence that this particular area is an
over-crowded fishing ground. There are enormous
numbers of plaice of 5, 6 and 7 inches in length. Even
in September, when the fish were, on the whole, largest,
there were only 30 per cent, over 8 inches long in the
sample catch. Now, plaice of 8 inches or thereabout do
not migrate out from shallow water. It is, probably, only
after they have grown to over this length that they move
out into the deeper channels, in large numbers at least.
While they remain in the shallow waters there are so
many of them that the available stock of food does not
appear to be sufficient ; the condition is below that of
plaice from most other fishing grounds; and they are
gradually destroyed by other animals. Thus the figures
in the tables show that average weight of plaice in Bock
Channel is significantly less than that on the other
grounds. I do not lay much stress on the figures for the
lengths of these plaice in each of the first two complete
years of their life, but so far as these figures go they
seem to show that plaice of Age-Group II (over two and
less than three years old), are smaller in Bock Channel
than they are on other grounds. In the samples of plaice
taken from this ground one does not notice a ffreat
increase in length as the year progresses. The fish remain
small all the time, for they do not grow quickly, and
their numbers are continually being added to from the
nursery area. There are too many of them, and they
might as well be captured by the fishermen as destroyed
by their natural enemies. In a certain sense we cannot

150 TRANSACTIONS LIVEIU'OOL RIOLOGICAE SOCIETY.

have too many plaice, if we could put them where they
would be of use to the industr}^ It is just the same as
the case of the small mussels ; if we can transplant a fair
proportion of the latter into grounds where they will grow
to be big enough to be marketable, then restriction of the
legal size would be of service to the industry ; but if we
do not transplant them, then (apart from economic
reasons) there is no reason why the fishermen should not
be allowed to take them. If we could transplant the
undersized plaice from such areas as Rock Channel to
other fishing grounds where they would grow well,
protection and restriction of the trawl-mesh might be of
advantage. But as it is, these restrictive regulations
appear to me to be of doubtful utility. Before one
advocates restriction of mesh on these grounds he ought
to be sure that this kind of regulation would result in an
increase of larger plaice elsewhere. Can we be sure that
this result would be produced?

Even if it were produced ; even if restriction of the
powers of capture within territorial limits were to lead
to an increase of larger plaice outside territorial limits,
would one be justified in advocating such restrictive
legislation ? For it would involve penalising the in-shore
fishermen possessing only small fishing vessels, or fishing
by stake-nets, trammels, or “ tees,’^ for the benefit of the
off-shore fishermen possessing sea-going boats. If the
public fish supply were to benefit greatly by such legisla-
tion it might be, on the whole, expedient that a few
fishermen should suffer for the advantage of the nation ;
but we should like to be quite certain that the benefit
would be very great compared with the suffering. These,
however, are economic questions which do not quite come
within the scope of a strictly scientific report.

It must not be forgotten that the settlement of the

SEA-FISHERIES LABORATORY.

151

question, for or against a 6-inch mesh, may depend on
future investigation. If the fish measurements carried
out during 1909 are repeated, on at least an equally large
scale in 1914, say, and if there were to he a significant
decrease in the average and modal sizes of plaice caught
by means of a 6-inch trawl-net in that year, then the
whole question will be looked at from quite another
aspect, and restriction of the powers of capture might be
conceivably necessary.

7. SIZES AT SEXUAL MATURITY.

Mature plaice are commoner in in-shore Lancashire
waters than snakes are in Iceland, but one cannot say
much more than this. Of some 2,500 plaice dissected
in the Liverpool and Piel Laboratory less than 50 were
identified as sexually mature. Spanning plaice are not
found in in-shore waters, and nowhere in the whole Irish
Sea in relative abundance except on the fishing grounds
about and between the Selker and Bahama Light Vessels.
- Doubtless they exist elsewhere, but in very small
numbers; and it is quite likely that the majority of the
young plaice inhabiting the nurseries on the Lancashire
and Cheshire coasts are spawned to the South-West, in
the St. George’s Channel and in the large Welsh bays.
Probably by much the smaller proportion comes from
the spawning grounds between Cumberland and the Forth
end of the Isle of Man.

In the late summer and autumn large mature plaice
immigrate for a month or two into shallow waters, and
such fish may be taken in Barrow Channel, Morecambe
Bay, in the Ilibble, and off the coasts and in the estuaries
of Forth Wales. It is mainly such fish that are handled
in the samples reaching us. The numbers are too small
to be treated statistically.

152 TRANSACTIONS LIVERPOOL WIOLOGICAL SOCIETY.

It is to be noted, however, that comparatively small
plaice have been found to be sexually mature. Some
females of 29*5 to 80*5 cms. (12 inches) were spawning
fish, and a fairly large proportion of male fish from 25 to
30 cms. (10-12 inches) long were mature and had fully
developed testes. This was the most novel part of this
section of the investigation. We had not previously
suspected that sexually mature plaice were so small as
the above figures indicate. The ages of these male plaice
were over three and less than four years. The mature
females w^ere very seldom less than four years old. It
has been suggested by Kyle that on intensely fished
grounds the average size of plaice, w^hen they first become
mature, is becoming less, and this hypothesis is very
probable. But another reason may well be that we simply
have not looked for these plaice in former years.

SEA-FISHERIES LABORATORY.

153

Tables. — Sizes of Plaice taken from the six-inch
Trawl-net, and other Data

Luce Bay and Firth of Clyde

Off

Corsewall
Point, Firth
of Clyde.

6"

Luce Bay.
6|"

Off

Corsewall
Point, Firth
of Clyde.

6"

Luce Bay.

i 6i"

June.

Oct.

June.

i Oct.

]\Iean

Mean ,

Length.

Length.

No.

O/

/o

No.

/o

No.

8/

/o

No.

0/

/o

10-5

_

1

006

I 34-5

1

40

2*42

11-5

—

—

—

—

i 35-5

3

—

30

1-82

12-5

—

—

1

006

! 36-5

2

—

27

1-64

13*5

—

—

—

—

37-5

4

—

19

M5

14-5

—

—

3

0-18

I 38-5

4

22

1-33

15-5

—

—

17

1-03

1 39-5

6

—

13

0-79

16-5

—

—

53

3-21

40-5

3

—

9

0-54

17-5

—

—

71

4-30

41*5

5

10

0-61

18-5

—

—

136

8-25

42-5

2

7

0-42

19-5

—

—

119

7-21

43-5

2

3

0-18

20-5

—

—

134

813

44-5

1

9

0-54

21-5

—

—

102

6-19

45-5

1

0-06

22-5

—

—

91

5-52

46-5

—

3

0-18

23-5

—

—

82

4-97

47*5

4

0-24

24-5

—

—

88

5-33

48-5

—

2

0-12

25-5

—

—

84

509

49-5

1

0-06

26-5

—

—

84

5-09

50-5

—

1

0-06

27-5

—

—

78

4-73

51-5

1

0-06

28-5

—

—

54

3-27

52-5

29-5

—

—

59

3-58

53-5

1

0-06

30-5

54

3-27

31-5

—

—

37

2-24

32-5

1

—

53

3-21

Total

35

1649

99-93

33-5

i

—

45

2-73

Near Bahama Bank and towards

Near Duddon Banks, 1909, 6" trawl-mesh 1 Seiker Light Vessel, 1909,

i 6" trawl-mesh

154 TRANSACTIONS LIVERPOOL BIOT.OGTCAL vSOCIETY.

1

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No.

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H

Fleetwood Channel, 1909, 6" trawl-mesh.

SEA-FISHERIES LABORATORY; 155

December.

O''

1

OO -^»C(MiOcOt-rj<OCO'^<M(MOOOOO
Tj< 00 1 O OI CO lO 00 CO O O GO 1

OO '-^i^idcbcdccidi^4i4iC'iGNioO'^o6 '

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No.

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September.

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to

(MOCOT*HOOt^OO-HF-HCOCO'<d^O<NO(M

1 |F^F^MOCpi^F^QO»OCOCOOr-iGOr-H'^ 1 1 1

' 'otdi'^ooriiMccodidi'idcsiodio ' ' '

99-97

3

No.

1 |f-hioco<mt^oooo»ococo<m»o<n»o^ I 1 1

1 ! --H (M <N <N (M (N (N ^ 1 1 1

00

CO

C0t-C0C'4C0C0t^Tj<t-.t2O»O10CCC0t-

t'

1 CO CO CO O O CO CO O CO C? t- CO CC CC CO CD 1 1 1 1

OS

*oocb^c66:>^':oc^^64<'^f-Hr-^o ' ' ' ’

ds

,_H ^ ^ ^ r— t

OS

6

|r-^(NF-HlOOOOTj^Ot'-'^<NCOCO'^TtH(M 1 1 1 1

OS

1 .— 1 ^ CO <M CO CO CO CO CO F-H ,— 1 1 1 1 1

OS

Ol

OOqcOiOCOiOCOOOCOCO'^OXiOOO OO

lO

1 IC^lO-HS^OMOOlOCO'^OOC^F^CSlCM |C^(N

OS

O ^

' '6cooG^idd3(dioc5cdcbdj(^Flioo 'coo

ds

c

^ ^ ^ _l ^

i

d

CM

1 1 — H (M lO t- lO CD uo Tt< CO F-F ^ -H 1

GO

COOCOOCOTt'lOCOXCOOO'F^iOO

1 ]OOI^COCOOOI:;'QOCX)GOOOC5| I I I I 1

o

o ^

' ■-^F^i^cbidcoi^dicdLdcdodio' ' ' ' ' '

6

1— ( F-( l-H ^

o

i

d

1 |CquOT^COOCOCOt>COIr-'^CO^| 1 1 1 1 1

(N

II llllll

o

Tt<G0-— ICOt^(MTt<Tt<(M'^t^'!t

\C

1 |lO^Ot-(MGOlOlOCOl-0(MlO| I I |<M| 1

OS

ds

c5

-- .—1 (M

OS

;h

.x:

o

Ph

d

1 |CC»Q01:^O-hC0(N(MC0(Mf-hc<j| I i IfhI |

Tt<

II -c llllll

I0i-0>00i0»0ic>ci0»0i0i0i0i0i0i0i0tci0»0i0

<D

toe

dicd-'^idcdt^cboOrPHCNicdrHidcdd'cbdiOFl-Gb

(<m<N(M(N(N(M<MC<I(M(MC0C0C0

1

4^

o

H

Barrow Channel, 1909, 6" trawl-mesh

156 TRANSACTIONS LIVERPOOL BIOLOGICAJ. SOCIETY.

I 1 I |(Nt^COCO(X)C005Tt<01(Ni3i'OCOCO| I I

Mil III

iOGO(MOTt<iO(MCO';C>0

I I I I Oi r-l CO 05 O 01 00 -H (M

' ' ' I (X 05 >0 ^ CO M CO ‘ ‘ ‘ '

I II I

I>"Ol:-T}<lOt'-CD^(MCO

Mill

p-

CO Ti^ O 00 o

I I I I II I 1 I I II 1 I

' ' ' 'i—

I I I I I I I I I I I I I I

05Tt<005050505050505
I I |XOrt<0(Nt-t;-cpcpQp
' I l(^i(:;5t^cboiooo-ic<jc<i' ' ' '

-H (N (M

I I I j(NO5<N00j^"ctiTt<(N(M(M| j | | |

CC 05 CO -I 05 M CO CO CC 23 CC

I I I |oo-hco-hoo9 0^9 9
I ' ' I 5^ o; lO 6 OO CO O CO CO CO CO

I I 1 I

CO O O CO '-H (N <N

I I II

05'^0500505-^'^05 05

I I I ' l(^^6dbco^cocO'^i:^'co(N‘ '-h

I j I I |(MI:^XCO(?a^C0C09(M|C0(Mj j

6r:^«^cb'^»ccoi^co650 9^co^og^ocoo

i.-<(M(N(M<NC<J(M<N(N<N(MCO

SEA-FISHERIES LABORATORY.

157

(

Barrow Channel, 1909, 6" trawl-mesh {continued)

Mean

Length.

f

1 July.

August.

October.

November.

December.

I

No.

%

No.

o/

/o

No.

1 0/

1 -

No.

0/

/o

No.

0/

/o

10-5

11-5

—

—

—

—

12-5

1 Q.p;

—

—

—

—

—

—

—

—

—

—

,14-5

z

z

~7

0-57

'l5-5

—

—

7

0-88

1

0-59

4

1-84

4

2-27

16-5

1

0-86

10

1-27

10

5-95

10

4-61

21

11-93

17-5

—

—

13

1-65

16

9-52

40

18-43

28

15-92

18-5

3

2-58

21

2-66

21

12-50

38

17-51

28

15-92

19-5

3

2-58

28

3-55

17

10-12

21

9-68

10

5-68

20-5

1 ^

4-31

54

6-85

17

10-12

22

10-14

22

12-50

21-5

3-45

51

6-47

13

7-74

16

7-37

14

7-95

22-5

15

12-93

119

15-10

11

6-55

23

10-59

11

6-25

23-5

15

12-93

105

13-32

12

7-14

13

5-99

11

6-25

24-5

1 21-

18-10

99

12-56 1

11

6-55

9

4-14

7

3-97

25-5

1 19

16-38

103

13-07 I

9

5-35

3

1-38

6

3-41

26-5

1 12

10-35

68

8-63 1

8

4-76

2

0-92

4

2-27

27-5 1

9

7-76

60

7-60

7

4-17

7

3-22

4

2-27

28-5 1

5

4-31

22

2-79

4

2-38

3

1-38

3

1-70

29*5 1

2

1-72

13

1-65

4

2-38

3

1-38

1

0-57

30-5 1

—

—

9

1-14

3

1-78

2

0-92

1

0-57

31-5 i

—

—

3

0-38

—

32-5

1

0-86

2

0-25

3

1-78

,

33-5

1

0-86

1

0-13

1

0-60

1

0-46

34-5

—

1

—

35-5

—

—

36-0

—

—

—

37-5

—

—

_

38-5

— .

—

39-9

—

—

1

40-5

—

- 1
i

—

—

—

—

—

—

otal ...

116 1

1

99-98

788

1

99-95 i

1

168

99-98

217

99-96

176

100-00

Near Nelson Buoy ; Blackpool Closed Ground, 1909, 6" trawl-mesh

158

TRANSACTIONS LIVKIIROOI. lUOLOGLCAI, SOCIKTY.

September.

■vO

o ■

r-H.-HTl<'^^r-iOCCiQOOCO'-l<0(MOO-l^cCiCGCO:OCOCC-H_^^fM
r-i ^ M t- o 00 >9 _iO lO 1;;- O lO 00 »0 O fO CO --H ^ .-H C^I

ooO'^ob-iosA'ot^coVbiAiGbbi^-^ooooooooo

99-97

No.

-^r^Tt^COOOOOl'-COt'OS^— <iO<MiO'+GCiCOfOfO—
^ lO ^ (M 05 O lO lO fC <M -H -H

902 1

August.

1

o/

,0

rlHOOCO(M005p^UOO»-OOC'-5 0CO-<4<CC'!t-f'^
|Tt<I:;-CO<NqOOO':^ipOuOOC>‘SO(rOTtiOti'+'^<Tti 1 l-^ 1 1 1

1

l§

|05

No.

Ir-H^CCTj^^MOOCOCOt-t^OOtMOCO-HCC— 1 Ir^ 1 1 1

1 ^C-lCOfMCsltM^— I-H II III

1

1 >-0
(M
1 Cl

t-lM'Mi-OCCfriOO'MCOcO'r+it^lO OO O

!

cc

1 1 1 |r-i005(:CC5QO(:OCO»OMCO-^I:;*|00| |'9 1 1 I

' ' ' 'i-^'tuG'iococ^cb'^oioM^'^'oo o '

6

•

r—i 1— ^ r-H 1— 1 f— 1

o

"3

6

1 1 1 |(NIOIOC005(MOO»OOOC5'^(MCOI^.^I 1^1 1 1

llll 1 11 III

1'

OOOC'l'^OOTti'^rtco-sOOOOOO o

CO

V. O

1 |^OOOOCOC005t^(M(NM^C5(MrtHCO'-^'^'^ \ 1 1 I 1

05

' i66c^io-^coccM(N6t^(Nrii66666 '6 ' * ' '

05

i-H 1— H fH 1— 1 1— H .-H

05

1-5

c

1 1— iOOGOC0005t-<M(NCC)^05(N'^eO-^-^-s |<M 1 I 1 1

CO

1 1 <M O ^ CO (TO (M (M O (M -H 1 llll

05

05

. 1

(X)F-I.^^COI:-^T)HCO--lTt<Tj<lOfOOTt<rJH

O

^Hfocodb-'^p^codiocbtoiO'^-^ci^C)

i I I

1 I

OOO05^00(MO0i-^C0OC0f0t'-

i I

t-C0Th0005Q000O

I 1

II II

5

$ ^

I0t0i0i0i0»0»0i0v0i0i0i0»0i0i0i0>0i0»0»pi0i0ici0i0 0 I
F^Mcb'^iooi^cbdio-^cbcb'^iocbr^GodiO'^fNcb'^irso | -f

Rock Channel, 1909, 6 ' trawl-mesh

SEA-FlSn ElUES LAHORATOEY.

It

CCCOOCCOlOOiTj^lOCOfOCO
1 1 1 1 1 — i i-H CO t- ,-H 00 CO ^ (M — 1 ffO 1 1 1 I

1

1

1 o

o

S

' ' ' ' ‘ <M di cd di 2 O ®

1

6

o

(U

1

1

W

i

1

d

j j 1 1 I |r-(— ICCC00M-10 05(M-HM| j 1 1

1

Ir-

;h

(Mir-ffOt^-^OfMOcO

1 1 1 1 1 1 .-H CO CD 00 t- O r-H »0 lO 1 1 1 1 1

* ' 1 ' ' IcdcbiOrHobidcd-^d^' 1 1 1 '

--H (M r-l CJ

1

99-97

Of

>■

o

No.

1 1 1 1 1 I O M ^ 1 1 1 1 1 1

CD

Ttl ^ Oi (N lO 00 to O CO CO CO

1 1 1 1 t- TfH tIh 00 Oi r-i ^ CO 00 <3i GO 1 1 1 01 1

1

tH

OS

oi

rQ

O

' ' ' 'cddbrHco^dit^dsdioo' ' 'o'

(N ^ f-H

1

ds

OS

o

o

No.

j 1 1 jT*HCiCO^COMOOOCO^p-H j 1 1

1

10^

D

it^COOOOOOOCNOqt^i-HF-HCDOO
1 1 1 1 It- CD CO lO 00 O O O t- t- CO I-H I |

1

CD

qs

ds

1 1 1 ' o ^ id CD CD cd cd id p-H o o o o ' ‘

r-4 (M ,— 1 ^

1

OS

O

m

No.

1 l.l |'^05O00O(N00i:^00p-<TiH'^(Nr-< 1 i 1

1 1 1 1 CO O lO O C- rt< (M ^ 1 '. 1

00

lO

no

00 r-- (M no O t- Tt< 1 OS CO tH 00

O 1 ID (M CO CO Tfi OS CO t- lO OS ^ O 1 j 1

1

o

o

(A

6 ' 6 6 id 6 cd cd r-H pH 6 6 6 o 6 ' ' '

r-H CO CO

o

»-S

No.

i-H 1 CD lO O O O CD CO CD rH 00 rH OS CO CO pH 1 I ? 1

1 iOOOiOt-iOOOCO--<'-H llll

h4 CO CO rH

1176

O-^COp-^Ot^COOOt^lOlfOlOCOOS'^lOlO
1 CO CO CO O CO qs lO t;- <» rH pH CO pH o O j 1

1

CO

OS

<s>

fl

o ^

'oop^cD'^iidcdt^idcD'^cdp^oooo ' •

CO CO pH

1

ds

OS

No.

IUOt^CDCOiO-HiiOT}HOOOiOOcOXCOpH.-H j 1 1

1 (MCOOSCOCOnOpH-^OOiOCO ’ll

pH no <M ^ pH ,-H

no

o

CO

>5

COO^t-O-^tiCOCOOCOOiOOnO
1 1 OS op P71 o CO qs op P71 ^ CO I | 1 ]

1

CO

o

' ' O O CC id d* M ^ 05 CD pH pH O O ' ' ' '

1

6

o

s

No.

1 1 PH IT- CO 00 CO O CO OS t- O Ttl OS CO CO 1 1 1 1 1

1 1 no pH CO pH O OS t- no pH 1 1 1 1 1

iH pH pH pH

00

tH

tH

iDpHCOCDOCOOCOpfnooOpHOcDHtHi'^OC'-'O
ococDcocooscoqsoot^-pH-^Ocoqsp^qipHO I

no

o

(M

OS

o'^

6copHp^cdpHidp^d-iddicdpHoo6 6o '

pH 00 01 pH

6

ds

OS

Sh

No.

^CD01CDOcDCDn0CD(XOSCD0STlH000S'pi<C0pH 1
— icoascDOOsci-^ospticooipH |

CO Hfl (M ^

-

1909

~~ !

!

rji CD OS -H csi I> oo CO no CO <M CD ^ CD no lO
1 pHCOOCOpHnOlOCOCOCOlOpHCppcD-^p^p^O'

1

CO

OS

'o 1

' o C dl CD d- dl d« pH d- id cd dl pH pH o o o o

pH <N -H ^ W

1

ds

OS

a !

S j

No.

I COCDCSCOnOpHCOOSp^nOOsCOOlOCOCOOSCO— ^ 1

1 cOCOCOhJIt*! — hJIO^O'^COOIpH 1

pH CO Tjl CO CO pH ,H

1952

Mean

sc

1 1

nononoionoioiononoioioioioioioioipioioioio

OpHdicdrhidcDd-cibdsopHcdcd'^vdcDd-ccdiO

p ^ ^ PH PH pH PH PH PH PH 04 CO <N 01 01 01 01 CO CO C-J CO

Total...

1()0 TKANSACTIONS IJVERP(J0L F^lOlAXilCAL SOCIETY.

Horse Channel, 1909, 6" trawl-mesh

June.

July.

August.*

Mean

length.

No.

o/

/o

No.

/O

No.

0/

/O

10- 5

11- 5

12- 5

1 1 1

—

—

—

2

0-14

13-5

—

—

1

0-12

17

1-20

14-5

8

1-42

21

2-47

56

3-97

15-5

44

7-80

26

3-05

88

6-24

16-5

84

14-89

67

7-88

122

8-65

17-5

80

14-18

93

10-93

151

10-71

18-5

86

15-24

103

12-10

140

9-92

19-5

75

13-28

112

13-16

138

9-79

20-5

68

12-05

123

14-46

139

9-86

21-6

53

9-40

105

12-33

117

8-29

22-5

35

6-20

85

10-00

122

8-65

23-5

14

2-48

61

7-16

104

7-37

24-5

8

1-42

20

2-35

96

6-82

25-5

3

0-53

9

1-06

53

3-76

26-5

3

0-53

6

0-70

31

2-19

27-5

1

0-17

4

0-47

24

1-70

28*5

1

0-17

7

0-82

5

0-35

29-5

1

0-17

—

—

3

0-21

30-5

—

—

—

—

2

0-14

31-5

—

—

2

0-23

—

—

32-5

—

—

1

0-12

—

—

33-5

—

—

1

0-12

—

—

34- 5

35- 5

36- 5

37- 5

—

—

—

—

—

—

—

—

1

0-12

—

—

38- 5

39- 5

—

—

2

0-23

—

—

40-5

—

—

1

0-12

—

—

Total

564

99-93

851

100-00

1410

99-96

Pai’t of catch lost through tearing of net.

SEA-FISHERIES LABORATORY.

161

Horse Channel, 1909, 6" trawl-mesh—

Mean

length.

September.

October.

November.

No.

%

No.

o/

/o

1

No.

0/

/o

10-5

_

_

_

_

11-5

.

12*5

13-5

1

0-09

—

—

—

—

14-5

4

0-39

—

—

—

—

15-5

5

0-48

—

—

—

—

16-5

29

2-83

4

1-76

12

3-34

17*5

90

8*79

16

7-05

30

8-35

18-5

99

9-67

30

13-21

48

13-36

19-5

99

9-67

31

13-67

67

18-66

20-5

123

12-01

24

10-57

47

13-09

21-5

118

11-53

28

12-34

37

10-30

22-5

107

10-46

16

7-05

39

10-86

23-5

76

7-42

17

7-49

37

10-30

24-5

75

7-32

13

5-73

13

3-62

25-5

58

5-66

14

6-17

12

3-34

26-5

55

5-37

11

4-84

7

1-95

27-5

30

2-93

6

2-64

2

0-55

28-5

28

2-73

7

3-08

3

0-83

29-5

14

1-36

5

2-20

2

0-55

30-5

5

0-48

2

0-88

2

0-55

31-5

7

0-68

—

—

1

0-28

32-5

1

0-09

—

—

—

—

33-5

1

0-09

—

—

—

—

34- 5

35- 5

1

0-09

1

0-44

—

—

36-5

37*5

—

—

1

0-44

z

— ■

38-5

QQ.ff

—

—

—

—

—

—

40-5

—

—

1

0-44

—

—

1'otal

1026

1

100-14

227

100-00

1 359

j 99-93

162 TRANSACTIONS LIVERPOOL HIOLOOICAL SOCIETY.

Near Mersey Bar, 1909, 6" trawl-mesh

June.

July.

September.

Mean

1

Length.

No.

?/o

No.

/o i

No.'

0/

/o

10- 5

11- 5

12- 5

—

1 1 1

—

0-42

5

1-36

13-5

1

0-21

1

0-42

6

1-63

14-5

—

—

3

1-26

16

4-36

15-5

5

1-07

6

2-52

31

8-44

16-5

15

3-18

15

6-30

41

11-17

17-5

43

9-13

29

12-19

49

13-36

18-5

55

11-67

18

7-56

32

8-72

19-5

59

12-52

34

14-28

30

8-17

20-5

74

15-71

36

15-13

28

7-63

21-5

55

11-67

36

15-13

18

4-91

22-5

43

9-13

25

10-50

26

7-09

23-5

29

6-15

13

5-46

18

4-91

24-5

26

5-52

10

4-20

16

4-36

25-5

14

3-00

5

2-10

10

2-72

26-5

7

1-48

3

1-26

8

2-18

27-5

12

2-55

1

0-42

13

3-54

28-5

9

1-91

1

0-42

4

1-09

29-5

8

1-70

1

0-42

5

1-36

30-5

6

1-27

—

—

4

1-09

31-5

2

0-42

—

—

2

0-55

32-5

3

0-64

—

—

2

0-55

33-5

2

0-42

—

—

1

0-27

34-5

—

—

—

—

2

0-55

35- 5

36- 5

37- 5

—

—

—

. —

—

—

1

0-21

38- 5

39- 5

40- 5

1

0-21

—

—

—

—

1

0-21

—

—

—

—

Total

471

99-98

238

99-99

367

1

i 100-01

1

Mersey Area, 1909, trawl-mesh.

SEA-FISHERIES LABORATORY.

CO 5.-, ^

163

CO f-H r-l 1:0 10 10
fO CO 00 (M 10 05

10 CO r-K

Tli(Ml:^CO00O5'Ft<,-HTj(t'.O5CO00':O<:DCC<M

CO

CO(M'-icX)OcO'Hr-(F-H(35lOOCOOOOOC»0 1 1 |r-i I

05

0^

occ-^cd'^0'4<cd4icddj^r-i^ooo 1 1 Ic5 1

6

• 01 <N r-H

<35

s

a

0

6

(NCOOOCOt'"FtiOOT*iCOiCCDCCC5iOiCCO | | 1— |

05

GC

^ •

CO -Ttf CO 00 CO O') -H Ol (M III 1

1C

C5

1 1 I |C000QCC0(M0C00F-i<:OF*00-^r-H^, I , ,

(35

1 1 1 |d5»didd5oididob^oidcoF^---l 1 1 1

i-H 1— 1 f-H

<35

6

1 1 1 |OCUO»OQO'^0>Ot-005iOCOr-F.-i| 1 1 1

o

1 1 1 1 F- ^ .1111

GO

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E-i

164 TKANSACTIONS LIVERPOOL RlOLOOiCAL SOtTETY.

Mersey Area, 1909, ¥ trawl-mesh

]\lean

Length.

Rock Channel.

Horse Channel.

Mersey Bar.
August.

Angust.

Angust.

September.

No.

%

No.

O'

/O

No.

o/

/O

No.

1

o/

/O

10-5

—

—

1

007

—

—

—

—

12-5

3

0-63

3

0-22

9

0-77

1

0-32

13-5

26

5-51

14

1-05

30

2-56

12

3-87

14-5

58

12-28

50

3-78

112

9-57

41

13-22

15-5

97

20-55

101

7-62

178

15-22

44

14-19

16-5

85

18-01

133

10-07

151

12-90

49

15-81

17-5

71

15-04

135

10-19

111

9-49

25

8-06

18-5 ■

47

9-96

150

11-29

78

6-67

21

6-78

10-5

29

6-14

103

7-77

58

4-95

12

3-87

20-5

21

4-45

116

8-75

65

5-55

32

10-32

21-5

13

2-75

114

8-60

70

5-98

23

7-42

22-5

12

2-55

147

11-09

61

5-21

22

7-09

23-5

3

0-63

120

9-06

53

4-53

10

3-22

24-5

2

0-42

59

4-45

54

4-61

8

2-58

25-5

2

0-42

36

2-72

58

4-96

6

1-94

26-5

1

0-21

15

1-13

30

2-56

—

— ■

27-5

1

0-21

10

0-75

24

2-05

2

0-64

28-5

1

0-21

2

0-15

14

1-19

—

—

29-5

—

—

10

0-75

6

0-51

—

—

30-5

—

—

1

0-07

6

0-51

—

—

31-5

—

—

1

0-07

—

—

1

0-32

32-5

—

—

2

0-14

1

0-08

1

0-32

33- 5

34- 5

—

—

1

0-07

—

z

35- 5

36- 5

—

1

0-08

—

—

o /•o

38*5

39- 5

40- 5

—

=

1

0-07

—

MM

i

M M i
i

—

Total . . .

472

99-97

1325

99-93

1170

99-95

310

99-97

SEA-FlSHEiUES LABOEATOKV.

165

Horse Channel and No. 6 Station, 1909, 7" trawl-mesh

September.

October.

November.

Mean

Length.

No.

0/

/o

No.

%

No. ,

%

10-5

_

_

_

_

_

11-5

12-5

13-5

14-5

1

0-08

—

—

—

15-5

2

0-17

1

0-73

1

0-28

16-5

8

0-69

8

5-88

2

0-57

17-5

29

2-48

27

19-86

30

8-59

18-5

54

4-63

29

21-32

68

19-48

19-5

108

9-25

18

13-23

63

18-05

20-5

138

11-82

6

4-41

54

15-47

21-5

113

9-68

11

8-09

38

10-89

22-5

115

9-85

6

4-41

29

8-31

23-5

119

10-20

5

3-68

24

6-87

24-5

146

12-51

2

1-46

7

2-00

25*5

110

9-43

6

4-41

11

3-15

26-5

82

7-03

4

2-94

10

2-86

27*5

63

5-40

3

2-19

1

0-28

28-5

35

3-00

4

2-94

7

2-00

29-5

17

1-42

3

2-19

2

0-57

30-5

7

0-60

2

1-46

—

—

31-5

4

0-34

1

0-73

—

—

32-5

11

0-94

—

— .

1

0-28

33-5

3

0-25

—

—

1

0-28

34-5

2

0-17

—

—

—

—

35*5

—

—

36-5

37-5

38-5

_

39-5

40-5

—

—

—

—

—

—

Total...

1167

99-94

136

99-93

349

99-93

166 TRANSACTIONS LIVERPOOL BIOLOGICAL S0CTI:TV.

Beaumaris and Conway Bays, 1909, 6" trawl-mesh

Mean

length.

June.

July.

September.

No.

%

No.

o/

/O

No.

o/

/o

10-5

11-5

—

—

—

—

2

0-12

12-5

—

—

2

0-26

6

0-37

13-5

—

—

1

0-13

6

0-37

14-5

—

—

3

0-39

17

1-04

15-5

1

0-67

24

3-16

24

1-47

16-5

10

6-75

37

4-88

73

4-46

17-5

16

10-81

87

11-48

104

6-36

18-5

19

12-83

101

13-32

104

6-36

10-5

27

18-24

116

15-31

124

7-59

20-5

18

12-16

93

12-27

107

6-54

21-5

16

10-81

94

12-40

87

5-32

22-5

17

11-48

57

7-52

112

6-85

23-5

7

4-73

43

5-67

122

7-46

24-5

1

0-67

37

4-88

121

7-40

25*5

2

1-35

18

2-37

116

7-10

26-5

2

1-35

7

0-92

123

7-52

27-5

4

2-70

4

0-53

96

5-87

28-5

2

1-35

6

0-79

99

6-05

29-5

2

1-35

6

0-79

53

3-24

30-5

—

—

7

0-92

41

2-51

31-5

—

—

—

—

33

2-02

32-5

2

1-35

1

0-13

21

1-28

33-5

—

—

3

0-39

14

0-86

34-5

1

0-67

4

0-53

10

0-61

35-5

—

—

2

0-26

6

0-37

36-5

1

0-67

2

0-26

4

0-24

37-5

—

—

—

—

4

0-24

38-5

—

—

3

0-39

1

0-06

39-5

—

—

—

—

1

0-06

40-5

—

—

—

—

4

0-24

Total

148

99-94

758

99-95

1635

99-98

SEA-FISIIERIES LABORATORY.

167

Beaumaris and Conway Bays, 1909, 6" trawl-mesh— Continued

* Mean
Length

October.

November.

December.

No.

o/

/o

1

No. 1

%

No.

o/

/o

10- 5

11- 5

12- 5

1

0-06

1 1 1

1 1 1

1

0-29

13-5

5

0-29

2

0-14

1

0-29

14-5

14

0-81

6

0-42

2

0-58

15-5

27

1-57

28

1-97

4

M7

16-5

78

4-53

69

4-87

13

3-80

17-5

143

8-30

103

7-27

14

. 4-09

18-5

137

7-95

102

7-20

13

3-80

19-5

100

6-15

88

6-21

17

4-97

20-5

88

5-11

77

5-43

20

5-85

21-5

83

4-81

89

6-28

21

6-14

22-5

77

4-47

75

5-29

25

7-31

23-5

103

5-98

89

6-28

26

7-60

24-5

102

5-92

121

8-54

27

7-89

25-5

125

7-25

127

8-96

25

7-31

26-5

154

8-94

102

7-20

19

5-56

27-5

122

7-08

89

6-28

16

4-68

28-5

115

G-67

81

5-72

12

3-52

29-5

93

5-40

54

3-81

13

3-80

30*5

63

3-65

40

2-82

16

4-68

31-5

40

2-32

26

1-79

17

4-97

32-5

19

MO

20

1-41

11

3-22

33-5

14

0-81

7

0-49

5

1-47

34-5

6

0-35

3

0-21

2

0-58

35-5

2

0-12

3

0-21

4

1-17

36-5

2

0-12

6

0-42

5

1-46

37*5

1

0-06

—

—

2

0-58

38-5

2

0-12

2

0-14

4

1-17

39-5

1

0-06

2

0-14

4

1-17

40-5

i

—

6

0-42

3

0-87

Total

i 1723

100-00

1417

99-92

342

99-99

168 TKANSACTIONS MVKJU'UOL HI OLlKi ICA J. SIM’IKTV

Red. Wharf Bay, 1909, 6" trawl-mesh

.Mean

June.

July.

August.

No.

%

No.

0/

/o

No.

O '

Jjength.

10-5

_

11-5

12-5

lH-5

—

14-.5

1

0-68

1

0-34

15-5

2

1-36

—

1

0-60

l(v5

8

i 5-44

4

1-37

1

0-60

17-5

1 18

12-2.5

9

3-09

8

4-76

18-5

i 18

j 12-25

16

5-50

8

4-76

19-5

1 26

' 17-69

27

9-28

18

10-72

20-5

9

6-12

40

13-74

11

6-55

21-5

1 8

5-44

42

14-43

25

14-88

22-5

9

6-12

39

' 13-41

32

19-04

23-5

9

i 6-12

26

! 8-93

17

10-12

24-5

()

1 4-08

22

7-56

17

10-12

25-5

4

2-72

14

4-81

9

5-34

26-5

5

3-40

12

4-12

7

4-16

27*5

3

2-04

8

2-75

3

1-78

28-5

4

2-72

3

1-03

1

0-60

29-5

3

2-04

5

1-72

3

1-78

30-5

2

1-36

4

1-.37

1

0-60

31-5

3

2-04

6

2-06

2

1-20

32-5

—

—

4

1-37

1

0-60

33*5

O

O

2-04

2

0-68

O

1-20

34-5

1

0-68

2

0-68

1

0-60

35*5

—

36-5

2

1-36

1

0-34

37*5

—

—

—

38-5

1

0-68

1

0-34

39'f)

1

0-68

1

0-34

40-5 ,

1

0-68

2

0-68

—

—

'L'otal...

147

99-99

291

99-94

168

100-01

S K A - F r vS J I ER 1 ES LA BO R ATOR Y .

169

Red Wharf Bay, 1909, 6" trawl-mesh — Conimmd

Mean

October-

November.

December.

Leiigth.

No.

%

No.

0/

/o

No.

%

10-5

—

—

—

—

—

11-5

—

—

—

—

—

—

12-5

—

—

— ■

—

—

—

13-5

1

0-90

1

0-20

1

0-09

14-5

3

2-70

1

0-20

rr

t

0-60

15-5

2

1-80

6

1-22

23

1-99

16-5

3

2-70

10

2-04

61

5-29

17*5

i-r

/

0-30

13

2-65

68

5-90

18-5

8

7-20

25

5-09

60

5-20

19-5

6

5-40

32

6-51

51

4-42

20-5

9

8*10

43

8-76

46

3-99

21-5

5

4-50

33

6-72

54

4-68

22-5

5

4-50

53

10-79

58

5-03

23-5

10

9-00

40

8-16

73

6-33

24-5

6

5*40

46

9-37

81

7-02

25-5

10

9-00

50

10-20

77

6-68

2G-5

11

9-91

25

5-10

'71

6-16

27-5

3

2-70

26

5-29

66

5-72

28-5

5

4*50

24

4-90

76

6-59

29-5

3

2-70

15

3-05

65

5-63

30-5

5

4-50

17

3-46

49

4-25

, 31-5

3

2-70

15

3-05

42

3-64

32-5

3

2-70

5

1-02

49

4-25

33-5

1

0-90

3

0-61

28

2-43

34-5

1

0-90

3

0-61

13

1-13

35-5

—

. —

2

0-40

13

M3

‘ 36-5

—

—

—

—

5

0-44

37-5

1

0-90

—

—

4

0-36

38-5

—

■ —

3

0-61

2

0-18

39-5

—

—

—

—

1

0-09

40-5

—

—

—

—

. 9

0-78

Total...

1 m

99-91

491

100-01

1153

100-00

170 TRANSACTIONS LIVERPOOL PIOLOGICAL SOCIETY.

Cardigan Bay, 1909, 6" trawl-mesh

Near Patches Buoy.

Near New Quay Head.

Mean

Length.

Jan.

Feb.

Mar.

February.

Mar.

April.

May.

No.

No.

No.

No.

%

No.

No.

0/

/o

No.

/o

16-5

1

4

3

4-41

3

0-69

17-5

—

—

2

—

—

1

6

8-82

26

6-05

18-5

—

4

1

—

—

1

—

—

29

6-74

19-5

—

—

1

1

2-5

1

6

8-82

35

8-14

20*5

—

1

1

2

5-0

2

2

2-94

40

9-30

21-5

1

1

1

1

2-5

2

2

2-94

34

7-90

22-5

1

—

6

—

—

7

7

10-29

25

5-81

23-5

3

2

—

—

—

2

5

7-35

35

8-14

24-5

1

8

—

3

7-5

2

11

16-17

24

5-58

25-5

2

4

4

3

7-5

15

7

10-29

28

6-51

26-5

5

7

7

4

10-0

9

6

8-82

46

10-70 ;

27-5

2

6

5

—

—

5

3

4-41

24

5-58

28-5

6

9

7

4

10-0

11

2

2-94

33

7-67 '

29-5

5

10

13

4

10-0

6

2

2-94

30

6-98 '

30*5

5

6

11

2

5-0

8

4

5-88

11

2-56

31-5

1

7

12

3

7*5

4

1

1-47

5

1-16

32-5

4

7

8

2

5-0

5

—

—

1

0-23 '

33-5

2

5

10

—

—

2

—

—

—

— i

34-5

1

4

6

4

10-0

1

—

—

1

0-23

35-5

4

3

5

1

2-5

1

—

—

—

—

36-5

2

1

4

1

2-5

3

1

1-47

—

—

37*5

3

2

3

i

2-5

3

—

—

-i-

—

38-5

—

2

2

—

—

3

—

—

—

—

39-5

1

2

3

1

2-5

—

—

—

— ]

40-5

Ai .rt

—

—

1

O

1

2-5

—

—

—

—

41*0

42-5

/i Q.rc

—

—

Z

1

1

—

1 1

1

—

—

—

—

4o’0

44-5

3

i

T

2*5

—

—

45-5

—

1

3

—

—

—

—

—

—

—

46-5

1

2*

2**

1

2-5

—

—

—

—

—

Total...

50

97

124

40

100-0

100

68

99-96

430

99-97

* 1 at 52 and 1 at 61.

** 53 and GO.

sp:a- f j sherip:kS laboratok y .

171

Near New Quay Head

Mean

Length.

June.

Mean

Length.

June.

No.

%

No.

/o

16-5

5

2-30

28-5

30

13-82

17-5

8

3-69

29-5

3

1-38

18-5

14

6-45

30-5

4

1-84

19-5

18

8-29

31-5

1

0-46

20-5

27

12-45

32-5

—

—

21-5

23

10-59

33-5

—

—

22-5

19

8-75

34-5

—

—

23-5

15

6-90

35-5

—

—

24-5

12

5-53

36-5

—

—

25-5

15

6-90

37-5

1

0-46

26-5

11

5-07

27-5

11

5-07

Total...

217

99-95

172 transactions Liverpool biologk'al socif/iv.

Age-Groups, 1909, Bahama Bank

[ February.

1

2

3

4

5

1

2

3

4 5

20*5

1

i

21-5

1

22-5

1

23-5

1

'

24-5

1

9

1

25-5

4

26-5

2

27-5

2

I

1

28-5

1

1

1

j

29*5

1 1

1

.30-5

1

1

1

i::::::

31-5

1

1

1

32*5

33-5

1

1

1

1

34-5

35-5

1

36-5

i

37-5

38-5

i

1

39-5

T '

40-5

1 .

41-5 1

Total...!

1 :

12

11

6

1

3

2

Age-Groups, 1909, Firth of Clyde, near Corsewall Point

June.

cJ !

i s

3

4

5

6

7

8

9

1 ^

4

5

6

7

8

9

20- 5

21- 5

22- 5

23- 5
24*5
25*5
2C-5

27- 5

28- 5

29- 5

30- 5

31- 5

32- 5

33- 5

1

1

1

1

1

1

1

i 1

1

1

1

1

2

2

1 ;

1

2

i

o

1

1

1

1

1

3

1

!

1

1

1

1

Total...

5

: 7

i

1

1

3

4

8

4

1

L

SEA-FISTIERIES LABORATORY.

Age-Groups, Barrow Channel, 1909

178

]\ra.rcli.

174 TKAXSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Age Groups, Barrow Channel.

Mean

Length.

July.

October.

$

$

1

2

3

1

2

3

1

2

3

1 '

2

3

10- 5

11- 5

12- 0

13- 5

14- 5

15- 5

16- 5
17*5

18- 5

19- 5

20- 5

21- 5

22- 5

23- 5

24- 5

25- 5

26- 5

27- 5

28- 5

29- 5

30- 5

31- 5

32- 5

Total...

3

2

2

....1

1

4

8

7

4

6

3

3 '
1 1

1

1

8

13

9

1

1

4

7
4

10

8
6
1
2

6

2

5
2

6

* 6
3
3
2

1

1

6

.5

.5

7

3

3

4

5
2
2

3

4

4
6
2
8

5
4
2
1
2
1

1

1

1

1

2

.....

1

1

1

1

1

1 1

1

2

2

47

1

3

1

43

7

44

4

4

' 36

i

2

33

j 34

4

Duddon Banks, 1909. Near Nelson Buoy, 1909

March.

June.

Mean

Length.

^ 1

$

1

1

2 1

i

3 1

1 ' 2

3

1

2

3

1

2

3

iU 0

i 1*0
1 9. Pi

1 Q.Pi

lO 0

14- 5

15- 5

16- 5

17- 5

O

1

O

5

5

4

4

]

3

2

i i

6

4

3

3

1

6

8

18 1

.5

12

1

8

1

10

3

18-5

10

! 12

1

4 '

15

1

' 21

2

2

1 1

19-5

2

5

2

1

2

1

33

3

23

3

3

20- 5

21- 5

22- 5

23- 5

24- 5

25- 5

1 2
! 2

1

1

1

1

2

11

7

1

3

15

22

10

o

5

1 1

!

4

4

i

1

1

! 1

1

1

1

1

o

Total . . .

33

1 40

1

4

1

20 :

35

5

8

|9,5

12

8

99

16

SEA-nSHEEIES LABORATORY.

175

Age-Groups, Rock Channel, 1909

hean

foigth.

February.

May.

June.

S

2

s

2

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

10- 5

11- 5

12- 5

13- 5

14- 5

15- 5

p-5

htl

24-5

[25-5

126-5

§7-5

ls-5

l9-5

io-5

1

1

1

5
13

6
1
2

2

2

4

18

15

10

8

2

1

1

1

1

3

2

5

6
14
10

9

3

1

1

3

3

11

19

17

15

12

6

9

7

8
8
5

1

1

1

1

1

1

1

8

5

1

1

9

7

5
14
17

6
6
4
1

2

3

7

1

1

2

4

3

2

1

2

2

3

2

1

2

1

4

3

7

6

1

1

1

3

1

1

2

1

1

1

1

i

1

(otal...

50

12

1

63

17

1

14

16

13

19

1

29 86

3

37

69

8

Mean

iength.

July.

October.

November.

S'

2

s

2

s

2

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

10- 5

11- 5

12- 5

13- 5

14- 5

!

4

5
11

6
7
4

1

7

15

7

4

5- 5

6- 5

7- 5

8- 5

9- 5

0- 5

1- 5

2- 5

3- 5
>4-5
>5-5
I6-5

7- 5

8- 5

9- 5

1

1

3

11

6

11

8

3

2

3

2

6

5

14

6
7
1
7
]

1

1

1

4

1

1

1

1

2

8

6

7

1

1

2

1

2

3

2

1

2

1

3

5

9

1

1

1

2

1

2

1

1

1

1

1

1

1

tal...

37

5

34

3

48

2

49

8

8

22

8

27

176 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Age-Groups, Fleetwood Channel, 1909

February.

Mean

Length.

10- 5

11- 5

12- 5

13- 5

14- 5

15- 5

16- 5

17- 5

18- 5

19- 5

20- 5

21- 5
22*5
23-5
24*5
25*5

26- 5

27- 5

28- 5

29- 5

30- 5

31- 5

32- 5

33- 5

34- 5

35- 5

36- 5

37- 5

38- 5

39- 5

1 2 3

1 2 3

March.

1 2 3

1

2

4
10

9

5

"l

1

2 3

September.

1 2 3

1 2

Total...

15

13

16

42

33

44

12

33

30

SEA-FISHERIES LABORATORY.

177

Age-Groups, Beaumaris Bay and Red Wharf Bay

July.

Mean

Length.

1

2

3

4

1

2

3

4

1

2

3

4

1

2

3

4

15-5

16-5

5

3

2

3

3

2

2

1

17-5

4

10

2

15

1

1

3

2

18-5

4

13

1

15

2

6

2

4

19-5

15

2

1

3

A

20-5

6

13

1

3

‘±

4

21-5

12

1

6

1

2

1

22-5

4

1

9

2

4

23-5

4

1

7

1

2

4

1

24-5

3

1

3

2

1

1

1

25-5

1

2

1

1

1

1

26-5

9

27-5

K

28-5

1

3

1

1

o

29-5

1

1

1

30-5

1

2

1

o

31-5

1

1

1

32-5

1

1

1

9

33-5

u

34-5

1

1

1

1

35-5

1

1

1

36-5

1

1

1

1

37*5

38-5

39*5

40-5

41-5

42-5

1

43-5

1

44*5

Total...

1

13

71

7

3

5

74

7

4

8

26

4

1

7

36

10

3

September.

178 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Age-Groups, Beaumaris Bay and Red Wharf Continued

December.

November.

(Red Wharf Bay.)

Mean

Length.

15- 5

16- 5
17*5

18- 5

19- 5

20- 5
2L5

22- 5

23- 5

24- 5

25- 5

26- 5
27'5

28- 5

29- 5

30- 5

31- 5

32- 5

33- 5

34- 5

35- 5

36- 5

37- 5

38- 5
39*5

40- 5

41 - A

42- 5
43 5
44-5

$

1

2

3

4

1

1

2

3

4

1

2

3

4

1

2

3

4

1

\

2

2

.1

2

1

2

1

1

3

1

o

2

1

1

1

2

2

2

2

2

1

1

3

1

3

1

3

4

1

2

-

6

3

1

1

2

1

1

1

2

2

1

1

1

2

1

1

1

1

3

3

1

2

3

4

1

4

1

1

4

3

1

1

3

1

2

1

1

1

1

2

4

1

1

1

2

1

1

1

1

, 5

8

2

9

19

6

1

7

21

9

2

2

23

23

5

Total..

SEA-FISHERIES LABORATORY.

179

Modal Lengths in Centimetres of Plaice captured by a
6^^ trawl-mesh, 1909

1 Localitv.
1

Duddon

Banks.

j Barrow
j Channel.

1

Fleetwood

Channel.

Nr. Nelson
Buoy.

j Horse
j Channel.

j Rock !

Channel. i

i 1

Nr. Mersey
Bar

Beaumaris

Bay.

03

^ .

Near New
Quay Head.

Jan.

—

17-6

(23-5)

(26-8)

1

Feb.

—

17-7

(22)

17-2

(23"2)

—

—

—

—

—

29-3

Mar.

18-4

17-8

18*4

16*8

(22-6)

—

16*6

—

—

‘ —

26-6

(37-4)

April

19-4

17-6

—

I —

—

17-4

—

—

—

24-2

(30-9)

May

19-7

18-5

—

j 21-6

1

j -

17*9

—

—

—

20*75

(27-1)

June

20*3

19-5

i 19-9

18-3

16-6

f21.0)

19-5 I

20*7

19-2

July

—

24-8

21-6

21-3

1 20-8

17-2

20*8

20-0

20-7

Aug.

— j

24-2

22-0

18-2

19-3

—

22*5

Sept.

—

222

1

17-8

21*5

19-1

17-9

18-9

(27-6)

—

—

Oct.

19-8

(18-9)

(28.1)

19-0 1

20-0

18-0

18*4

(26-0)

19-2

(25-4)

Nov.

19-5

(27*8)

—

20-0

—

—

181

(26-1)

23-0

—

Dec.

18-6

—

— j

24*8

(31-6)

18*2

(26-8)

—

Values of the Length-Weight Coefficient k, 1909

^ 9

Locality.

[ Duddon
Banks

Barrow 1

Channel

Fleetwood I
Channel. j

Nr. Nelson
Buoy.

Near Rock
Channel.

*

cS

a

§

c ce
MW

Menai

Straits.

Carnarvon
Bay. I

January

0*923

0*987

0*931

0*968

0*981

1*00

1*16

1*16

l-20t

l-07t

1*00

0*865

1*00

0.8Q7

0*866

0*765

0*912

0*884

n.Qi *7

February

March

0*924

1*09

w y i 6
n. A'TO

April

1*00

May

u y i /
1*02
1*00
1*10
0*949

1 .HQ

0*977

June

0*943

1*06

1*09

July

i

August

1 Uo
1*16
1 .HQ

September

1 Uu
1*08
0*966
1*01
1*03

1*06

October

November

1*06

1*05

1*01

0-965

December

* Includes Red Wharf Bay. t Interpolated values.

180 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Modal Lengths of Plaice of Age-Groups I and II, 1909.

Locality

Barrow Channel.

Duddon Banks.

1

j Near Nelson Buoy.

Sex

$

$

C?

S i

Age-

^

Group

1

2

1

2

1

2

1

2

; 1

2

1 ^

1 ^

Jan.

17-8

17-6

1

—

Feb. ...

19

23*1

18-9

22-6

—

i _

March ...

17-5

—

17-1

—

18-4

18-3

17-6

18-2

April ...

—

—

—

—

—

j __

May

18

—

18-75

June ...

—

20-2

—

20-2

—

1

16-5

19-8

16-25, 20-

July ...

—

22

—

22

Aug. ...

—

—

—

;

Sept. ...

—

—

—

!

[

i •

Oct.

18-7

21-9

18-9

22-6

H 1 I]

Nov. ...

—

Dec. ...

■ 1

—

—

—

—

_

—

—

— i —

1

1 1

Jan.

Feb. ...
March ...
April ...
May

June ...
July ...
Aug. ...
Sept. . . .
Oct.

Nov. ...
Dec. ...

Rock Channel. j Beaumaris Bay. Fleetwood Channel.

_

1

1

1

1 _

17-6

21-2

18-2

21-5

—

—

—

—

16-3

17-5

16-5

22-

—

—

—

—

—

—

—

17-4

19-8

17-3

20-;

—

—

—

1

—

—

. •

17-0

20-8

18-5

20-7

16-1

19-5

16-4 1

19-5

J

17-0

—

' 17-2 !

—

—

19-5

—

19-75

1 1

—

—

I'

Ji

—

—

—

—

—

19-6

20-9

18

24-7

18-5

2I]

19-1

—

19-1

—

—

22-2

—

21-2

—

24-2

—

24-2

-1

1

22-5

—

22-5

—

—

—

)>;

SEA-FISHERIES LABORATORY.

181

Plaice, Age-Group II, Male. Catch of 44 from Barrow
Channel, 12 July, 1909.

Mean length
in cents.

Frequency

(observed).

Frequency

(smoothed).

Deviation
from mode,
cr

Theoretical

frequency.

17-5

1

1

1-72

1-7

18-5

4

4

1-29

3-29

19-5

7

5

0-86

5-23

20*5

4

7

0-43

6-9

21-5

10

7*3

—

7-58

22-5

8

8

0-43

6-9

23-5

6

5

0-86

5-23

24-5

1

3

1-29

3-29

25-5

2

1

1-72

1-7

26-5

—

1

2*15

0*65

27-5

1

1

2-58

0-26

Standard deviation = a = 2*32.

Mode = 21’9 (taken as 21*5).

2 errors^ = 238*1.

Tl

Maximum ordinate ^ 7*58.

V 2 7T

Length-Frequencies, Grpup II, Males ; Nelson Buoy, June
1909. Comparison with Normal Curve of Error.

Mean length
in cents.

Frequency.

Smoothed

frequency.

Deviation
from mode,
cr

Theoretical

frequency.

15-5

1

1

2-4

1-26

16-5

3

4

1-8

4-48

17-5

‘8

10*7

1-2

11-01

18-5

21

20*7

0-62

18-69

19-5

33

21*7

—

22-66

20*5

11

17

0-62

18-69

21-5

7

9-3

1-2

11-01

22-5

10

6

1-8

4-48

23-5

1

1

2-4

1-26

No. of observations = n = 91*4.

Arithmetic average = 19*52.
Empirical mode = 19*5.

Standard deviation =

(T — 1*61.

Sum of errors squared, ^ 8^ = 238*5.

n

Maximum frequency = = 22*66.

^ ^ o- V 2 7T

182 TRANSACTIONS LIVERPOOL lilOLOGiCAL SOCIETY.

Length-Frequencies, Group II, Females ; Nelson Buoy,
June 1909. Comparison with Normal Curve of Error.

Mean length
in cents.

Frequency.

Smoothed

frequency.

Deviation
from mode.
cr

Theoretical

frequency.

15-5

2

2

2-4

1-08

16-5

6

6

1-9

3-17

17-5

10

9

1-4

7-26

18-5

11

14-7

0-99

11-85

19-5

23

16-3

0-5

17-08

20-5

15

20

—

19-37

21-5

22

14

0-5

17-08

22-5

5

10-3

0*99

11-85

23-5

4

3

1-4

7-26

24-5

—

1-7

1-9

3-17

25-5

1

1

2-4

1-08

n = no. of observations = 98.
Arithmetic average = 20*03.

Empirical mode = 20*5.

X = Sum of errors squared = 409*88.

I ^

Standard deviation, a, = ^ = 2*019.

n

Maximum frequency = = 19*37.

^ V 2 7T

SEA-FISHERIES LABORATORY.

188

Measurements of 200 Plaice hatched at Port Erin on 26 April,
1906, and examined on 27 May, 1907.

Limits

Actual

i

of

Distance from

Nos.

x>

fix) xN

Length

mode in

between

—

(calcu-

in

inches.

limits.

c

lated

inches.

x'

/

Nos.)

11 to 11

-1-375 to 1-125

2

-1-72

0*493 1

3-12

H „ If

-1-125 „ 0-875

1

-1-4

0-476^

6-9

5 0-038

li » 2

-1-875 „ 0-625

20

-1-09

0-438

0-076

13-9

2 „ 21

-0-625 „ 0-375

26

-0-77

0-362

21-16

0-115

21 „ 21

-0-375 „ 0-125

29

-0-47

0-247

28-8

0-157

( -0-16

0-090

21 „ 2|

-0-125 ,,+0-125

37

]

0-180

33-1

i+0-16

0-090 ^

} 0-157

2f „ 3

+0-125 „ 0-375

25

+ 0-47

0-247

0-115

28-8

3 „ 31

+ 0-375 „ 0-625

24

+ 0-77

0-362 ;

21-16

0-076

31 „ 31

+0-625 „ 0-875

12

+ 1-09

0-438

13-9

0-038

31 „ 31

+ 0-875 „ 1-125

4

+ 1-4

0-476

6-9

0-017

31 „ 4

+ 1-125 „ 1-375

4

+ 1-72

0-493^

3-12

4 „ 41

. —

8

41 „ 41

N — 184 (the part of the series

5

above 3| to 4 being neglected) .

41 „ 4f

—

Standard deviation

=

4f „ 5
5 „ 51

—

—

(T =

- JsU'/)

V N

= 0*505.

51 „ 51

—

1

Modulus = c = V‘2,.cr = 0’712.

51 „ 5|

—

1

Mode is at 2*625 inches.

1 I

f (x) is I e - rZx, the equation for the integral

V 7T j 0

curve of error. Values are tabulated in Bowley’s Elements
of Statistics, ed. 2, 1902, p. 281.

f{x)xN are the nos. of fish on the algebraic
occurring between the limits in Column I.

curve

184 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Partial Catches Measured Twice.

A : On board S'.S. “ James Fletcher ” when alive.
B ; At Liverpool Laboratory about 24 hours later.

Nos. at and above each centimetre in length.

Conway Bay
27.11.09

Conway Bay

17.11.09 ‘

Conway Bay
22.909

Conway Bay
23.7.09

A

B

A

!

B

A

B

A

1

B

14-5

lOl.

101

202

202

15-6

51

51

51

51

99

99

201

200

16-5

50

49

r '• (

49

98

97

192

194

17-5

47

44

48

46

89

89

183

181

18-5

43

42

44

40

80

82

148

150

19-5

42

41

39

38

68

68

120

117

20-5

40

38

36

36

59

60

92

91

21’5

38

36

32

31

62

52

71

72 .

22-5

36

33

29

27

49

48

49

53

23-5

32

32

26

26

40

42

37

38

24-5

31

30

23

20

35

35

24

25

25-5

26

23

19

17

33

33

16

16

26-5

21

17

16

14

28

30

13

13

27-5

16

14

14

11

27

28

28-5

13

11

10

23

23

11

11

29*5

11

7

5

5

16

16

10

10

30-5

7

5

15

15

9

9

. 31-6

3

3

11

11

6

32-5

3

3

8

8

6

33-5

2

2

2

4

5

5

5

34-5

3

4

35-5

1

2

3

3

3

36-5

1

2

2

2

37-5

1

1

38*5

39-5

1

1

j

.

40-5

1

1

Total

51

51

51 1

i

51

101

101

202

1

202

SEA-FISHERIES LABORATORY.

185

THE HYDROGEAPHIC WORK IN THE IRISH
SEA DURING 1909: A POSSIBLE BEARING
ON METEOROLOGICAL WORK.

By Henry Bassett, Jun., D.Sc., Ph.D., Assistant
Lecturer in Chemistry in the University of Liverpool.

The hydrographic work carried out by us in the
Irish Sea during 1909 has followed the lines indicated at
the end of last year’s report.* Quarterly observations at
the 15 stations indicated on the chart (p. 186) have been
made, while additional observations at stations 1 to 7
were made half-way between the quarterly cruises, the
samples, as usual, having been collected by my colleague,
Mr. J. Johnstone, B.Sc.

In the tables which follow, T°, Cl °/oo> ^ 7oo>
have the usual meanings.

A discussion of the results, which seem to be of
unusual interest, is given after the tables.

Jan. 25 to 29, 1909.

Station I. 25/1/09 (2.25 p.m.). 54^ N. ; 3° 30' W.
Depth of station, 29*3 metres.

Depth (metres)

rpo

Cl 7oo

S7oc

o-t

0

5-2

18-03

32-57

25-75

25

5-2

18-03

32-57

25-57

Station II. 25/1/09 (3.25 p.m.).

, 54° N. ; 3° 47' W.

Depth (metres)

rjio

ci7co

S7oo

o-t

0

5-8

18-29

33-04

26-06

1

♦Trans. Biol. Soc. of Liverpool, Vol. XXIII., p. 146 (1909);- also
Lancashire Sea Fisheries Laboratory Report, No. iv, p. 44 (1909).

186 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Fig. 21. Hydrographic Stations during 1909.

, SEA-FISHERIES LABORATORY.

187

Station III. 25/1/09 (4.25 p.m.). 54° K ; 4° 4' W.

Depth (metres)

rjio

Cl 7oo

o

o

CO

o’t

0

64

18-52

33-46

26-30

Station lY. 25/1/09 (5.10 p.m.). 54° N. ; 4° 20' W.
Depth of station, 47' 6 metres.

Depth (metres)

rpo

Cl 7oo

S7oo

o-t

0

7-7

18-73

33-84

26-43

45

7-6

18-72.

33-82

26-44

Station Y. 27/1/09 (11.30 a.m.). 53° 53' N. ; 4° 46' W.
Depth of station, 100’7 metres.

Depth (metres)

rpo

ci7co

S7oo

o-t

0

8-3

18-74

33-86

26-35

50

8-15

—

—

—

100

8-2

18-74

33-86

26-36

The samples for Station Y were actually collected
from a point about one mile W. of the correct position
(given above).

Station YI. 27/1/09 (10.25 a.m.). 53° 43' N. ;

4° 44' W. Depth of station, 60'4 metres.

Depth (metres)

IJIO

Cl 7oo

S7co

o-t

0

8-4

18-78

33-93

26-39

25

8-3

—

—

—

58

8-3

18-77

33-91

26-39

188 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station VII. 27/1/09 (9.25 a.m.). 53^^ 33' N. ;

4° 41' W. Depth of station, 53'1 metres.

Depth (metres)

rpo

ci7oo

S7oo

o-t

0

8-15

18*81

33*98

26*48

25

8-1

—

—

—

50

8-1

18*79

33*95

26*46

Station

VIII. 26/1/09 (12.20

p.m.). 54° 4' X.;

3° 28' W. Depth of station, 29’3 metres.

Depth (metres)

(JIO

ci7„o

S7oc

o-t

0

5-3

18*05

32*61

25*77

25

5-2

18*05

32*61

25*78

Only surface observations were taken at the following
stations : —

Station.

Date and Time.

fJiO

Cl 7oo

S7oo

o-t

IX.

54° 9' N.; ,3°44'W.

26.1.09 (11.30a.m.)

5*9

18*46

33*35

26*29

X.

54°12'N. ; 4°W.

26.1.09(10.40 a.m.)

6*0

18*55

33*51

26*41

XI.

53°54'N. ; 3° 59' W.

29.1.09 (9.45 a.m.)

6*8

18*71

33*80

26*52

XII. 53° 47' N. ; 3° 45' W.

29.1.09 (10.45 a.m.)

6*1

18*51

33*44

26*33

Station XIII. 29/1/09 (11.45 a.m.). 53° 39' N. ;

3° 30' W. Depth of station, 29'3 metres.

Depth (metres)

rpo

Cl 7oo

S7oo

o-t

0

5*65

18*33

33*12

26*13

26

5*5

18*33

33*12

26*14

station XIV. 26/1/09 (5.30 p.m.

). 53° 30' N.

; 4°1'W.

Depth (metres)

rjio

«7oo

8 7oo

o-t

0

7*5

18*83

34*02

26*60

SEA-FISHERIES LABORATORY.

189

March 19 to 21, 1909.

Station I. 19/3/09 (11.10 a.m.). 54° K ; 3° 30' W.
Depth of station, 25*6 metres.

Depth (metres)

rpo

Q

.o

o

s7o=

o-t

0

4-95

18-32

33-10

26-19

24

4*7

—

—

—

Station II. 19/3/09 (12 noon). 54° N. ; 3° 47' W.
Depth of station, 42*1 metres.

Depth (metres)

rjio

ci7oo

S7co

o-t

0

5-5

18-48

33-39

26-38

40

5-2

—

—

—

Station III. 19/3/09 (1 p.m.).
Depth of station, 42*1 metres.

, 54° N. ;

4° 4' W.

Depth (metres)

rpo

Cl 7oo

S7oo

o't

0

5-85

18-64

33-68

26-56

40

5-65

—

—

—

Station lY. 19/3/09 (2 p.m.).
Depth of station, 49 metres.

54° N.;

4° 20' W.

Depth (metres)

rjlO

Cl 7oo

S7co

o-t

0

5-75

18-65

33-69

26-57

47

5-5

—

—

—

190 TRANSACTIONS LIVERROOL BIOLOGICAL SOCIETY.

Station y. 19/3/09 (3.50 p.m.). 53° 53' N. ; 4° 46' W.
Depth of station, 65’9 metres.

Depth (metres)

rpo

o

o

O

s7„o

o-t

0

6-6

18-78

33-93

26-65

35

6-5

—

—

—

63

6-55

18-78

33-93

26-65

station VI. 19/3/09 (4.65 p.m.). 53"

4° 44' W. Depth of station, 64’9 metres.

’ 43' N.;

Depth (metres)

rjio

C, 7oo

S7oo ■

0

6-7

18-81

33-98

26-68

25

6-47

—

—

—

52

6-45

18-81

33-98

26-71

Station

YII. 19/3/09 (5.50 i

p.m.). 53"

’ 33' N.;

4° 41' W. Depth of station, 56*7 metres.

Depth (metres)

rpo

ci7„o

S7oc •

o-t

0

6-3

18-81

33-98

26-74

25

6-15

—

—

—

55

6-15

18-82

34-00

26-76

Temperature observations alone were made at
stations YIII to XIY.

For the rest of the year the line of soundings
Nos. XI to XIY was slightly altered so as to run from
the Calf of Man to the Liverpool North West Lightship.

May 17 to 19, 1909.

Station I. lT/5/09 (11.30 a.m.). 54° N. ; 3° 30' W.
Depth of station, 27*4 metres.

Depth (metres)

fJlO

C! 7oc

8 7oo

o-t

0

10-35

18-16

32-81

25-21

25

8-85

18-17

32-83

25-47

SEA-FISHERIES LABORATORY.

191

: Station II. IT/5/09 (12.30 p.m.). 54° N. ; 3° 47' W.

Depth of station, 38’5 metres.

Depth (metres)

/JIO

Cl 7oo

S7oo

o-t

0

10-05

18-34

33-13

25-52

35

8-35

—

—

—

Station III. IT/5/09 (1.25 p.m.). 54° ~N.; 4° 4' W.
Depth of station, 42‘I metres.

Depth (metres)

rjpo

ci7oo

S7oo

o-t

0

8-9

18-65

.33-69

26-13

38

8-55

—

—

—

Station IT. IT/5 09 (2.25 p.m.
Depth of station, 51‘2 metres.

). 54° N. ;

O

o

Depth (metres)

rj!0

Cl

S7co

0

8-9

j 18-85

34-05

26-41

49

8-65

1 18-86

i

34-07

26-48

Station Y. 18/5/09 (8.25 a.m.).
Depth of station, lOO'I metres.

53° 53' JT. ;

; 4° 46' IV.

1

Depth (metres)

rjio

Cl 7oo

1

S°/

^ too

1

o-t

0 '

8-53

18-93

34-20

26-59

10

8-42

—

—

50

8-42

—

—

—

100

8-42

18-93

34-20

26-61

N

192 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station VI. 18/5/09 (9.30 a.m.). 53° 43' N. ;

4° 44' W. Depth of station, 63*5 metres.

Depth (metres)

T°

Ci7c„

1

S7oo '■

1

o-t

0

8-5

18-94

34-22

26-60

10

8-3

—

—

—

30

8-3

—

—

—

63

8-3

18-94

34-22

26-63

Station VII. 18/5/09 (10.25 a.m.). 53° 33' N. ;

4° 41' W. Depth of station, 82*4 metres.

Depth (metres)

rpo

Cl V

loo

8%o

o-t

0

8-7

18-90

34-14

26-52

10

8-6

—

—

—

30

8-6

—

—

—

80

8-45

18-90

34-14

26-56

Only surface observations were taken at the following
stations : —

Station.

Date and Tijne.

T°

Cl 7oo

S7oo

o-t

VIII. 54° 4' N. ; 3° 28' W.

19.5.09 (10.50 a.m.)

9-3

18-29

33-04

25-56

IX. 54° 9' N.; 3° 44' W.

19.5.09 (9.55 a.m.)

9.05

18-30

33-06

25-62

X. 54° 12'N. : 4° W.

19.5.09 (8.55 a.m.)

8.95

18.31

33-08

25-64

Station XL 18/5/09 (6.45 p.m.). 53° 56' X. ;

4° 31' W. Depth of station, 58*6 metres.

Depth (metres)

fpo

ci7oo

S7co

o-t

0

8-80

18-87

34-09

26-46

55

8-75

—

—

—

SEA-FISHERIES LABORATORY.

193

Station XII. 18/5/09 (5.30 p.m.). 53° 48' X. ;

4° 11' W. Depth of station, 4T‘6 metres.

Depth (metres)

fJIO

Cl 7oo

S7„o

o-t

0

8-83

18-77

33-91

26-31

43

8-65

—

—

—

Station XIII. 18/5/09 (4.25 p.m.).
3° 51' AA^. Depth of station, 42‘1 metres.

53

° 41' X. ;

Depth (metres)

rjio

ci7oo

s7oo

o-t

0

9-1

18-48

33-39

25-87

40

8-7

—

—

—

Station XIAh 18/5/09 (3.10 p.m.).
3° 31' AA^. Depth of station, 31*1 metres.

■53° 31'

Depth (metres)

(JIO

ci7oo

S7co

o-t

0

9-5

18-19

32-86

25-39

30

9-1

18-22

32-92

25-50

Station
4° 6' AAh

XAh 18/5/09 (1.10 p.m.).

53°

’ 26' X.;

Depth (metres)

rjio

Cl 7oo

s7„o

1

' o-t

0

9-3

18-57

33-55

25-96

June 14 to 18, 1909.

Station I. 14/6;09 (1 p.m.). 54° X.; 3° 30' AV.

Depth of station, 2T‘5 metres.

Depth (metres)

rjpo

Cl 7oo

S7oo

o-t

0

12-4

18-27

33-01

24-99

24

10-7

—

—

—

194 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station II. 14/6/09 (2 p.m.). 54° N. ; 6° 47' W.

Depth of station, 68‘4 metres.

Depth (metres]

1

rpo

ci7„o

S7oo

0

12-5

18-41

33-26

25-16

35

10-65

i

—

—

Station III. 14/6/09 (6 p.m.)
Depth of station, 4-3‘9 metres.

. 54° N.;

4° 4' AY.

Depth (metres)

rjiO

ci;/oo

S7oo

o-t

0

13-33

18-30

33-06

24-85

40

10-5

—

—

—

Station lY. 14/6/09 (4 p.m.).
Depth of station, 49'4 metres.

54° N.; ^

4° 20' AY.

Depth (metres)

rjio

ci7oo

S7oo

o-t

0

11-73

18-85

34-05

25-92

46

10-65

—

—

—

Station Y. 14/6/09 (5.40 p.m.).

63° 6-3' N. ;

4° 46' AY.

Depth of stat:

ion, 69’5 metres.

Depth (metres)

rpo

ci7oo

s7oc

0

10-62

18-90 i

34-14

26-20

30

10-00

1

—

—

65

10-00

18-89

34-13

26-29

Station YI. 14/6/09 (6.50 p.m.). 53°

4° 44' AY. Depth of station, 69*5 m.etres.

43' N.;

1

Depth (metres)

rjpo

ci7oo

s7oo

o-t

0

10-1

18-95

34-23

26-36

30

9-85

—

— 1

—

65

9-8

18-95

34-23 1

1

26-41

SEA-FISHERIES LABORATORY.

195

Station VII. I4/G/09 (7.55 p.m.). 53° 33' N. ;

4° 41' W. Depth of station, 65’9 metres.

Depth (metres)

fJIO

Cl 7oo

8%o

o-t

0

10-42

18-95

34-23

26-29

30

10-25

—

—

—

62

10-25

18-94

34-22

26-31

Two sets of observations were made on the June trip
in the deep w^ater off the Mull of Galloway.

54° 34' 30" F. ; 5° W. I6/G/09 (I0.40-II a.m.). Depth
of station, 256‘2 metres.

Depth (metres)

rjio

Cl 7oo

S7cc

o*t

0

9-45

18-78

33-93

26-22

50

9-10

18-79

33-95

26-30

100

8-87

18-81

33-98

26-36

220

8-75

18-81

33-98

26-39

54° 50' N. ; 5° 19' W. 16/6/09 (1.45-2 p.m.). Depth
of station, 245*2 metres.

Depth'(metres)

ci7„o

s7oo

CTt

0

9-35

18-79

33-95

26-26

50

8-61

18-79

33-95

26-38

100

8-55

18-79

33-95

26-39

230

8-51

18-79

33-95

26-40

July 26 to 28, 1909.

Station

I, 20/7/09

(2 p.m.).

54° N.; 3° 30' W.

Depth of station, 23*8 metres.

Depth (metres)

rpo

ci7oo

s7oo ^

0

14-73

18-19

32-86

24-40

23

14-60

18-19

32-86

24-43

196 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

station II. 26/7/09 (3 p.m.). 64° N.; 3° 47' W.

Ueptli of station, 34‘8 metres.

Depth (metres)

rjio

ci7oo

S7oo

o-t

0

13-87

18-52

33-46

25-03

30

13-6

—

—

—

Station
Depth of stat

III. 26/7/09 (4 p.m.).
ion, 45'8 metres.

54° N. ;

4° 4' W.

Depth (metres)

rjio

Cl 7oo

8 7co

o-t

0

13-65

18-58

33-57

25-16

40

13-15

—

Station IV. 20/7/09 (5 p.m.). 54° N. ; 4° 20' W.

Depth of station, 43'9 metres.

Depth (metres)

fjio

o

o

O

S7oo

o-t

0

12-95

18-78

33-93

25-58

40

12-75

18-80

33-96

25-66

Station V. 27/7/09 (8 a.m.). 53° 53' N. ; 4° 46' W.
Depth of station, 80’5 metres.

Depth (metres)

rpo

Cl%„

s7oo

o-t

0

12-45

18-88

34-11

25-83

30

12-00

—

—

—

75

11-77

18-94

34-22

26-04

SEA-FISHEEIES LABOEATORY. 197

Station VI. 27/T/09 (9.15 a.m.). 58° 48' N. ;

4° 44' W. Depth of station, 58' G metres.

Depth (metres)

(JIO

Cl %o

S7co

o't

0

12-80

18-88

34.11

25-76

30

12-45

—

—

—

55

12-45

18-90

34-14

25-86

Station yil. 2T/7/09 (10.25 a.m.). 58° 83' N. ;

4° 41' W. Depth of station, 53' 1 metres.

Depth (metres)

rpo

ci7oo

8 7oo

0

13-3

18-82

34-00

25-57

30

12-8

—

—

—

50

12-75

18-91

34-16

25-81

Only surface observations were made at stations
VIII, IX and X.

Station.

Date and Time.

T°

Cl

S7oo

o-t

Vlll. 54° 4' N. ; 3° 28' W.

28.7.09 (8.15 a.m.)

15-15

18-10

32-70

24-18

IX. 54° 9' N.; 3° 44' W.

28.7.09 (7.55 a.m.)

14.15

18.41

33.26

24.83

X 54° 'l2'N. ; 4° W.

28.7.09 (6.30 a.m.)

13.75

18-46

33-35

24-99

Station XI.

27/7/09 (8.40 p

>.m.).

53°

5G'

N,;

4° 81' W. Depth of station, 67'T metres.

Depth (metres)

rjio

Cl 7co

S7oo

o-t

0

12-5

18-87

34-09

25-81

30

12-1

—

—

—

63

12-05

18-90

34-14

25-94

198 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station XII. 27/7/09 (7 15 p.m.). 53° 48' N. ;

4° 11' W. Depth of station, 51'2 metres.

Depth (metres)

T°

Cl 7„o

S7oc

o-t

0

48

12-65

‘12-4

18-87

34-09

25-78

Station XIII. 27/7/09 (0 p.m.). 53° 41' X.;

3° 51' W. Depth of station, 45'8 metres.

Depth (metres)

T°

Cl 7

^ loo

S7„o

o-t

0

42

13-75

12-85

18-55

18-74

33-51

33-86

25-11

25-54

vStation XIV. 27/T/09 (4,25 p.m.). 53° 31' N. ;

3° 31' W. Depth of .station, 31'1 metres.

Depth (metres)

rjto

Cl 7o.

S7oo

o-t

0

25

14-0

13-8

18-39

18-41

33-22

33-26

24-84

24-90

station XV. 2T/7/09 (12.50 p.m.). 53° 26' N.;

4° 6' W.

Depth (metres)

rjio

Cl 7o„

s7oc

o-t

0

14-0

18-53

33-48

25-03

September 14 to 17, 1909.

Station I. 14/9/09 (1.20 p.m.). 54° X.; 3° 30' W.
Depth of station, 22 metres.

Depth (metres)

r|io

ci7o„

S7op

o-t

0

14-55

18-36

33-17

24-68

21

14-15

—

—

—

SEA-FISHERIES LABORATORY.

199

Station II. 14/9/09 (2.20 p.m.). 54° N. ; 4° 47' W.
Deptli of station, -34’8 metres.

Depth (metres]

fJIO

Cl 7oo

S7oo

o-t

0

1445

18-60

33-60

25-03

34

14-0

—

—

—

Station III. 14/9/09 (3.16 p.m.). 54° N. ;
Depth of station, 42'1 metres.

4° 4' W.

Depth (metres)

rjio

Cl 7oo

8 7co

o-t

0

14-0

18-73

33-84

25-31

40

13-7

—

—

—

Station lY. 14/9/09 (4.5 p.m.)
Depth of station, 45*8 metres.

. 54° N. ;

4° 20' W.

Depth (metres)

rjpo

ci7„„

S7oo

o-t

0

13-6

18-84

34-04

25-55

45

1

13-5

—

—

—

station V. 14/9/09 (5.25 p.m.).
Depth of station, 58'6 metres.

53° 53' N. ;

4° 46' W.

Depth (metres)

ci7oo

S7oo

o-t

0

12-9

18-81

33-98

25-65

30

12-8

—

—

—

57

12-8

18-81

33-98

25-67

200 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station VI. 14/9/09 (6.20 p.m.). 53° 43' N. ; 4° 44' W.
Depth of station, 63'5 metres.

Depth (metres)

rpo

Cl 7oc

S7oo

0

13-08

18-85

34-05

25-66

30

12-95

—

—

—

63

12-95

18-85

34-05

25*68

Station VII. 14/9/09 (7.20 p.m.j. 53° 33' N.;
4° 41' W. Depth of station, 98*8 metres.

Depth (metres)

fjio

Cl 7oo

S7oc

o-t

0

13-4

18-88

34-11

25-64

30

13-25

—

—

—

90

13-3

18-88

34-11

25-66

Only temperature observations were made at stations

VIII to XV.

November 1 to 4, 1909.

Station I. 2/11/09 (4.15 p.m.).
Depth of station, 29*3 metres.

54° X. ;

3° 30' W.

Depth (metres)

rpo 1

!

ci7o„

s7oo

0

110

18-55

33-51

25-64

26

10-77

18-55

33-51

25-68

Station II. 2/11/09 (12.20 p.m.
Depth of station, 42*1 metres.

). 54° N.;

3° 47' W.

Depth (metres)

rjio

ci7oo

S7oo

o-t

0

11-7

18-63

33*66

25-62

39 ^

11-5

. —

—

—

SEA-FISHERIES LABORATORY. 201

Station III. 2/11/09 (11.30 a.m.). 54° N. ; 4° 4' W.
Depth of station, 43'9 metres.

Depth (metres)

rpo

o

o

o

S7co

o-t

0

11-6

18*73

33-84

25*79

40

11-5

—

Station IV. 2/11/09 (10.25 a.m.). 54° N. ;

Depth of station, 49'4 metres.

4° 20' W.

Depth (metres)

(JIO

f

Cl 7oc

S7oo

o-t

• 0

11*47

18*80

33*96

25*90

45

11*40

18*80

33*96

25*92

Station Y. 4/11/09 (9.25 a.m.).
Depth of station, 80*5 metres.

53° 53' N. ;

4° 46' W.

Depth (metres)

rj40

Cl 7co

S7oo

1

i

i

0

11*57

18-72

33*82

25-78

30

11*37

—

—

i —

75

11*32

18-74

i

33*86

i 26-85

Station yi. 4/11/09 (10.30 a.m.). 53° 43' N. ;

4° 44' W. Depth of station, 58*6 metres.

Depth (metres)

rjio

ci7oo

s7oo

o-t

0

11*8

18*79

33*95

25*83

30

11*67

—

—

—

54

11*67

18*79

33*95

25*85

‘202 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Station YII. 4/11/09 (11.45 a.m.). 53° 33' N. ;

4° 41' TV. Depth of station, 58'G metres.

Depth (metres)

. 'po

Cl

o-t

0

12-1

18-73

33-84

25-69

30

11-95

—

54

11-95

18-72

33-82

25-70

Only surface observations were made at stations
VIII, IX and X.

Station.

Date and Time.

rjio

Cl 7oo

S7oo

o-t

VIII. 54° 4' N. ; 3° 28' W.

IX. 54° 9' N. ; 3° 44' W.

X. 54° 12' N. ; 4° W.

1.11.09 (3.30 p.m.)
1.11.09 (4.25 p.m.)
1.11.09 (5.20 p.m.)

11-25
11-25
9-95 j

18-65

18-69

18-31

33-69

33-77

33-08

25-74

25-79

25-48

Station XI. 3/11/09 (3.10 p.m.). 53° 56' N. ; 4° 31' W.
Depth of station, 58'6 metres.

Depth (metres)

rpo

ci7oo

S7oo

o-t

0

11-7

18-79

33-95

25-85

54

11-6

18-80

33-96

25-88

Station

XII. ;i/II/09 (1.45

p.m.). 53'

^ 48' X.;

4° 11' VV. Depth of station, 47*6 metres.

Depth (metres)

/JIO

Cl 7oo

S%„

o-t

0

11-8

18-73

33-84

25-74

42

11-7

—

—

—

SEA-FISHERIES LABORATORY.

203

Station XIII. '3/11/09 (12.20 p.m.)." 53° 41^ X.;

3° dV W. Depth of station, 43‘9 metres.

Depth (metres)

rpo

ci7oo

s7oc

o-t

0

11*5

1844

33-31

25-40

40

11'37

18-39

33-22

25-35

Station

XIY. 2/11/09 (4.15

p.m.). 53

° 31' X.;

3° 31' AY. Depth of station, 34‘8 metres.

!

Depth (metres)

rjio

1

Cl 7oo

GC

(3

O

o-t

0

10-9

17-95

32-43

24-82

33

10-9

18-03

32-57

24-93

The temperature observations made at stations YIII
to XY during the March, June and September cruises are
given in Mr. Johnstone’s paper in the present report.

In order to show the seasonal variation of the
salinities more clearly, the values for the surface salinities
at the various stations are collected in the accompanying
table.

Table illustrating the seasonal variation of the
surface salinities at the various stations during 1909.

i Jan.

March

May

June

July

Sept.

Nov.

Station

1 25-29

19-21

17-19

14-18

26-28

14-17

1-4

1 1909

1909

1909

1909

1909

1909

1909

I

■ .32-57

33-10

32-81

33-01

32-86

33-17

33-51

11

1 33-04

.33-39

33-13

33-26

33-46

33-60

33-66

III

j 33-46

33-68

33-69

33-06

33-57

33-84

33-84

IV

33-84

33-69

34-05

34-05

33-93

34-04

33-96

V

33-86

33-93

34-20

34-14

34-11

33-98

33-82

VI

33-93

33-98

34-22

34-23

34-11

34-05

33-95

VII

33-98

33-98

34-14

34-23

34-00

34-11

33-84

VIII

32-61

—

33-04

—

32-70

—

33-69

IX

33-35

—

33-06

—

33-26

—

33-77

X

33-51

—

3.3-08

—

33-35

—

33-08

XI

33-80

—

34-09

—

.34-09

—

33-95

XII

33-44

—

.33-91

—

34-09

—

33-84

XIII

33-12

—

33-39

—

33-51

—

33-31

XIV

34-02

—

.32-86

—

33-22

—

32-43

XV

—

—

33-55

—

33-48

—

—

204 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

V A comparison of the foregoing table with the
corresponding ones given in the two previous reports will
at once show that the hydrographic conditions prevailing
in this area during 1909 were very different from those
existing in 1907 and 1908, and, so far as one can tell from
the incomplete data, in 1906 also.

It is more especially stations Y, YI and VII which
we have to consider. These are the three stations which
are affected by the Gulf Stream Drift, and where, in
consequence, the maximum salinity usually occurs about
February. This year, however, it will be seen that the
maximum occurs much later than this, namely, in May
and Tune, which we must regard as quite abnormal. And
moreover, not only is the maximum much later, but it is
also less well defined, and the salinity is somewhat lower
than in previous years (34*2 instead of 34*4 °/oo). The
salinity variations at the remaining 12 stations, where the
variations are chiefly due to varying amounts of fresh
water flowing in from the neighbouring coasts, are more
irregular, but on the whole the maximum salinities tend
to occur during the autumn. The figures for stations lY,
XI and XII suggest, however, that at these stations the
tendency of the Gulf Stream Drift to cause a Spring
maximum of the salinities is barely counterbalanced by
the effect of the fresh coastal water.

The temperatures at nearly all the 15 stations are
considerably different from those found during the period
1906-1908, so far as the various stations which — with the
exception of Xos. Y, YI and YII— have not always been
quite the same, are comparable. During the first half of
1909 the temperatures were considerably higher than in
previous years, while during the latter half of the year
they were a good deal lower than usual.

The natural conclusion to draw from these results is

SEA-FISHERIES LABORATORY.

205

tliat during 1909 the Gulf Stream Drift was much later
than usual in making itself felt in the Irish Sea, and that
when the Atlantic current did appear it was of lower
salinity and lower temperature than usual.

The late arrival of the Atlantic current would plainly
dela}^ the Spring maximum of the salinity at all points
directly under its influence. It seems to me that the
later arrival of the Atlantic current of lower temperature
than usual would also account for the departure of the
water temperatures from the normal which has been
mentioned above.

As the Atlantic current was late, the warmer water
from the end of the previous year would remain in the
Irish Sea much longer than usual, and the \vater tempera-
tures in the early parts of the year would consequently be
above the normal ; when, however, this water had been
swept northwards by the inflowing and colder Atlantic
water, the temperatures would fall below those found in
more normal years. It may be mentioned here that the
results obtained by the Irish Board of Agriculture and
Technical Instruction, under Mr. E. W. L. Holt, which
will be referred to more fully in the next article, fully
bear out our conclusions that the salinities at points in
the Irish Sea affected by the Gulf Stream Drift were at a
maximum in May and June of 1909.

Xow we know that the weather during 1909 was most
unusual, and it seems reasonable to ' conclude that the
abnormal weather and the abnormal Gulf Stream Drift
were intimately connected.

Although the rainfall over the British Isles as a
whole during 1909 was exactly equal to the average in
amount, it was most abnormally distributed. The amount
of rain which fell in the South-west of Ireland, Wales and
England, and the North-west of Scotland, was con-

206 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

siderably below the average, while the vSouth and East of
Great Britain were much wetter than nsual.*

The temperatures during 1909 were also unusual, and
in spite of a few warm months, the year as a whole seems
to have been colder than usual.

A short discussion of the weather of each month of
1909, by E. J. Brodie, will be found in Symons’s Meteoro-
logical Magazine for 1909 (Vol. 44), where rainfall tables
for the various months are also given. Many features of
the weather seem to agree very well with what might be
expected. Thus the rainfall for January and February
was a good deal below the average, while March was much
colder than usual, both of which facts can be accounted
for by the absence of the large body of warm Atlantic
water. In the same way the extreme dryness of August
and September in the South of Ireland may well be due
to the fact that the Atlantic water in the neighbourhood
was colder than usual. This would, of course, result in
the winds blowing from the sea to the land not being so
heavily charged with moisture as usual, and a smaller
precipitation on the land in consequence.

It is not, of course, for one moment to be understood
that these important effects on the weather are to be
attributed to the hydrographic conditions prevailing in
the Irish Sea. The body of water in the latter is
probably far too small for variations in its condition to
have more than a -very slight inlluence on the weather,
and that only at places actually on the shores of the Irish
Sea itself. It seems, however, reasonable to regard the
tongue of Atlantic water which flows up the Irish Sea as
an index of the Gulf Stream Drift as a whole, and it is to
be expected that variations in the latter will aflect the
weather of these Islands, and, in fact, of North-west
See an article in “ The Times ” of Jan. 14th, 1910, by Dr. H. E. Mill.

SEA-FISHERIES LABORATORY.

207

Europe. We know, of course, that the immediate causes
of tlie weather in the British Isles are to he sought in the
movements of the various cyclonic and anti-cyclonic
systems in the neighbourhood. These, however, are
probably influenced to a very large extent by the position
and nature of the Gulf Stream Drift for the time beins*.
The Gulf Stream Drift itself is largely regulated by the
general nature of the winds due to the huge cyclonic
system which rests over the North Atlantic with its centre
at Iceland.*

Variations and abnormalities in the Gulf Stream
Drift may therefore he expected to have an influence on
the weather over extended periods of time, whereas the
weather over shorter periods is dependent chiefly on the
smaller cyclonic and anti-cyclonic systems then pre-
vailing. In accordance, therefore, with these considera-
tions, I wish to put forward the hypothesis that the
peculiar weather of the past year is directly traceable to
the late arrival of the Gulf Stream Drift, coupled with its
unusually low temperature (due probably to greater
admixture with Arctic water of low salinity).

Future work must prove or disprove this hypothesis,
which I have some hesitation in bringing forward owing
to the scantiness of the hydrographic data available. The
mere accumulation of hydrographic data is, however, of
minor interest. The interest lies with the deductions
which may be made from the data. This, therefore, is my
excuse for pointing out a possible line of work to which
attention should be paid.

If the hydrographic conditions of the Irish Sea and
the Atlantic Ocean at the mouths of the Irish Sea and
English Channel are studied for a number of years, it
should soon be possible to see whether any connection can

* Meinardus. Meteorologische Zeitschrift XXII, 398 (1905).

208 TRANSACTIONS LIVERTOOL BIOLOGICAL SOCIETY.

be traced between the state of the Gulf Stream Drift in
these parts and the weatlier of the British Isles. If, as
seems to me probable, an affirmative answer can be given
to this query, it may Avell prove possible to predict the
general character of the summer and autumn of any year
from hydrographic observations made during February
and March of the same year at the mouth of (or even in)
the Irish Sea and English Channel. In the same way
observations made during the summer would perhaps give
an indication of the probable nature of the succeeding
winter.

W. Meinardus* in a very striking paper has shown
that there is a very intimate connection between the
general circulation of the air in the North Atlantic region
(which forms one large barometric unit), the marine
Atlantic currents, and the weather of North-west Europe.
Thus he shows that a weak atmospheric circulation over
the North Atlantic during August-Eebruary corresponds
to (I) low water temperatures on the coast of Europe
during November- April ; (2) low air temperatures in

Central Europe from February- April ; (3) little ice off
Newfoundland during the spring; (4) plenty of ice off
Iceland during the spring ; (5) bad wheat and rye harvests
in Western Europe and North Germany. A strong
atmospheric circulation over the North Atlantic during
August-Eebruary corresponds to exactly the opposite.

Helland-Hansen and Nansen, in an important paper,t
have shown that the character of fhe summer in Northern
Norway (and many important things depending upon
this, such as the Lofoten cod fishery, the harvest, and so
on) can be predicted a year, or even two years, in advance

* Meteorologische Zeitschrift XXII, 398 (1905).

t Internationale Kevue der gesamten Hydrobiologie und Hydro-
graphie II, 337 (1909).

SEA-FISHERIES LABORATORY.

209

from tlie results of liydrograpliic observations made off
tbe South- west coast of Norway.

In conclusion, it may be stated that tbe present year
may perhaps furnish a test of the views expressed in the
latter part of this paper. Our hydrographic observations
made at stations Y, YI and YII on 2/2/10 have given
values for the salinities practically identical with those
found on 2T/1/09. I feel confident, therefore, that the
Gulf Stream Drift is late again this year, and think it
very probable that the weather during summer 1910 may
be similar to that of summer 1909 in consequence. This
seems likely if the late Drift is also colder and fresher
than usual, as it was last year. Whether this is always
the case with a late Drift we have not yet sufficient data
to show, but from Meinardus’ observations (loc. cit.) it
seems probable. Of course if, when the Gulf Stream Drift
does arrive, it is salter and warmer than usual, we shall
almost certainly not have the same kind of summer as wc
had in 1909.

210 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

THE FLOW OF WATER THROUGH THE
IRISH SEA.

By Henry Bassett, Jun., D.Sc., Pli.D., Assistant
Lecturer in Chemistry in the University of Liverpool.

In my reports on the Hydrographic work in tlie Irish
Sea during 1900, 1907 and 1908,* I assumed that there was
a general flow of the vfater from Soutli to North, without,
however, discussing the point. It seems, however, high
time that this important point should he fully discussed,
and for two reasons. In the first place, because it is being
assumed by some people that exactly the reverse is the
case, and that the water flows southwards from the Irish
Sea ; and in the second place, because the data now
available are, for the first time, sufficient to prove wdthout
a shadow of doubt that the water does actually flow from
South to North. Even before any detailed hydrographic
work had been done in the Irish Sea, generally known
facts were sufficient to show that in all probability there
was a flow of water through the area from South to North
— the current passing to the East of the Isle of Man.

, Thus the general set of the tides points in this
direction, the tides towards the North nearly always being
stronger than those toAvards the South.

Then again, the sand and shingle on the English and
Welsh and on the Irish coasts tend to travel northwards.!

It is a well known fact that practically all wreckage

* Trans. ^ Biol. Soc. of Liverpool, Vol. XXII., p. 145 (1908), and
Vol. XXIII., p. 146 (1909) : also Lancashire Sea-fisheries Laboratory
Reports, No. 16, p. 54 (1908), and No. 17, p. 44 (1909).

t Mr. C. D. Oliver, M.Inst.C.E., Engineer to the Dept, of
Agriculture and Technical Instruction for Ireland, in reply to enquiries
kindly made for me by Professor Grenville Cole, quotes numerous cases
which have come under his observation and which in his opinion
show that the sand on the East Coast of Ireland travels from South
to North, though probably very slowly.

SEA-FISHERIES LABORATORY.

211

from the southern parts of the Irish Sea drifts northwards
and is eventually washed up on the coast of Lancashire
and Cumberland, that is to say, exactly where a current
from South to North, and passing to the East of the Isle
of Man, would be expected to take it. The same thing
almost invariably happened to bottles thrown overboard
by Professor Herdman.^'

Bearing these facts in mind, it seems somewhat
strange that anyone should assume that the flow of water
through the Irish Sea was in the contrary direction,
especially since, even neglecting the above-mentioned
facts, it w’as a 'priori improbable.

It is well known (“ Law of Ferrel ”) that owing to
the circulation of water from the poles to the equator and
back to the poles, coupled with the rotation of the earth
about its axis, the marine currents in the Northern
Hemisphere tend to flow from S.W. to N.E. in the case of
warm currents, or from N.E. to S.W. in the case of cold
currents.

The Gulf Stream is one of the former, and, as is well
known, flows round the North of the British Isles to the
Norwegian Coast. It has been known for several years
that a small branch of the Gulf Stream passes through the
English Channel, and it was to be expected also that some
of the eastward flowing water would succeed in forcing
its way through the Irish Sea.

A current flowing southwards through the Irish Sea
might be one of two kinds. It might be a cold current,
which, however, would be flowing in rather the wrong
direction (namely, a somewhat easterly one) for a cold
current. It is, however, clear that it would be impossible
for such a cold current to get down the Irish Sea, for to
do so it would first have to cross the Gulf Stream flowing
Trmis., Biol. Soe. of Liverpool, XVII,, p. 154 (1903).

212 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

round tlie North of Ireland and Scotland. It could only
do this by going under it, which would require deep water
such as does not exist to the North of Ireland, for the
deep channel which runs through the western parts of the
Irish Sea and the North Channel does not reach further
than G° 40' W. Any other possible southward flowing
current could ouly be a small eddy-like branch of the
Gulf Stream. Since, however, the southern opening of
the Irish Sea is much wider and more conveniently
situated than the northern opening, it is far more
probable that a tongue of the Gulf Stream would run
through the Irish Sea from South to North, and not from
North to South.

The results we obtained in 1908 would be very hard
to explain by means of a southward flowing current.
(See the chart in the Eeport of the Hydrographic Work
in the Irish Sea during 1908.)

Mr. D. J. Matthews,"^ of the Marine Biological
Association, as a result of his hydrographic investigations
in the English Channel, came to the conclusion that water
from the Irish Sea spread southwards over the English
Channel, and J. N. Nielsenf has suggested in consequence
that there is an anti-cyclonic circulation of the water
round Ireland.

When Matthews’ evidence is examined carefully,
however, it seems to point conclusively in the opposite
direction. In the Second Eeport of the North Sea
Fisheries Investigation Committee, Part II — Southern
Area — (London, 1909), Matthews gives charts in which
all the available hjMrographic observations for 1904 and

* IMatthews, Report on the Physical Conditions in the English Channel,
1903. First Report of the North Sea Fisheries Investigation Committee
[Southern Area), London, 1905.

t Medclelelser fra Kommissionen for Havundersogelser . Hydrografi,
Vol. I., No. 9, Copenhagen (1907).

SEA-nSHERIES LABORATORY.

213

1905 are plotted and isolialines drawn which seem to hear
out his contention that a current of water of low salinity
is flowing southwards from the Irish Sea.

I have re-drawn the charts (see Plates II to Y)
putting in the numerical values for the salinities of the
various points indicated on Matthews’ charts. Nearly
all of the numerical data are given in the above-mentioned
Second Report, Part II, hut a few of them had to he
obtained from the Second Report, Part I — Southern
Area — (London, 1907), while a few were obtained from
the Bulletins trimestriels du Conseil permanent inter-
national pour I’exploration de la Mer ” for 1905, A few
other flgures, not utilised apparently by Matthews, but
also referring to the same period, were found in Part I
of the Second Report. These have also been introduced
into the charts of the present paper, hut are specially
indicated. I have tried to draw the isohalines on the
charts as fairly as possible, and have also indicated by
dotted lines how Matthews draws the same. It seems to
me that my way of drawing the lines is in better agree-
ment with the flgures, and also gives a reasonable
explanation of the facts, but it must, of course, he
admitted that the data are too scanty to enable one to
draw the isohalines with any great certainty.

It wull he seen at once that the isohalines indicate a
current of water flowing northwards up the Irish Sea with
a tendency to strike St. David’s Head. At the same time
there is a small tongue of low salinity water coming
South round Land’s End. It was the presence of this
water which led Matthews to think that there was a
southward flowing current from the Irish Sea.

This tongue of water seems, however, relatively
insigniflcant, and is almost certainly derived not from the
Irish Sea, but from the Bristol Channel, and is probably

214 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

carried southwards by an eddy resulting from the tongue
of Gulf Stream water striking St. David’s Head and being
diverted southwards as indicated in the figure. The fact
that this tongue of fresher water is much less prominent,
and even cut off altogether by salter water towards the
end of the year, when the Gulf Stream Drift is at a
minimum, is in good agreement with this view. It would
evidently he exceedingly interesting to study the hydro-
graphic conditions in the Bristol Channel, and future
work should also carefully look for the narrow tongue of
salt water running across its mouth.

It seems probable that the above-mentioned eddy
would only be sufficiently strong to carry Bristol Channel
water southwards during the spring, when the Gulf
Stream Drift is at a maximum. It appears that along the
North coast of Cornwall sand accumulates on the western
side of the headlands,* which indicates that the total
movement of the water towards the North-east is greater
than any movement to the South-west.

The conditions during 1904 seem to have been some-
what different from those found during 1905, but the data
available are somewhat scantier than for the latter year.

I have also re-plotted the charts for 1904, but do not give
the results in this paper, as they are too doubtful. The
isohalines, as drawn by Matthews in the charts for 1904,
do not disregard the values of the salinities at some of the
stations, as in the 1905 charts, but it is also possible to
draw them somewhat differently and bring them more
into line wuth those for 1905, as re-drawn in the present
paper. When this is done, islands of fresher water to the
South of the Land’s End appear in the charts for August
and November somewhat similar to that in the chart for

* I am indebted to the Eev. W. Milburn Briggs for this
information.

SEA-FISHERIES LABORATORY.

215

November, 1905. The tongue of salter water passing up
the Irish Sea seems to be much less pronounced than in
1905, and the charts also seem to suggest that in 1901 the
Gulf Stream Drift struck the Land’s End instead of
striking against St. David’s Head. This is also rendered
more probable by Gough’s observations “ On the distribu-
tion and the migrations of Muggiaea atlantica (Cunning-
ham) in the English Channel, the Irish Sea, and ojffi the
South and West Coasts of Ireland in 1904.”*

Only a few isolated hydrographic observations made
by the “ Helga ” in the Irish Sea during 1905 have been
published (Bulletins trimestriels). During 1909, however,
the “ Helga ” made a detailed hydrographic survey
of the whole Irish Sea with the exception of the portion
to the East of the Holyhead-Calf of Man line which we
have been investigating from Liverpool since 1906.
This hydrographic work was carried out under the
direction of Mr. E. W. L. Holt, of the Irish Department
of Agriculture, and Mr. Holt has very kindly given me
permission to make use of his figures (which will be
published in the Bulletins trimestriels for the current
year). I have, therefore, introduced Holt’s and our own
figures for 1909 on the same charts as Matthews’ figures
for 1905, as no figures for a date later than 1905 are
available for the southern area.

It is evident that the curves drawn for 1909 are not
directly comparable with those drawn for 1905, and to
make this clear on the charts a narrow uncoloured strip
has been left between the two sets of curves. Although
this combination of the two sets of curves may be open to
criticism, it is useful for our present purpose of discussing
the flow of water through the Irish Sea. The figures and

* Publication dc Circonsfance, No. 29, du Conseil permanent
international pou7' V exploration de la Mer. Copenhagen, 1905.

216 TRANSACTIONS LIVERROOL BIOLOGICAL SOCIETY.

curves in tlie Irish Sea speak, I think, for themselves. It
would hardly be possible to draw the isohalines
substantially different from the way in which they are
drawm on the charts, and it is clear that such a distribu-
tion of salinities can only be explained by a flow of water
from South to North.

The figures on the charts refer to surface salinities,
hut the Irish Sea is practically homosaline throughout,
and where any dih'erences of salinity with depth do occur
they are small, and do not affect the above conclusions.
The isohalines show very plainly how the northward
flowing current tends to flow along the eastern side of the
Irish Sea. They also show that a great deal of the water
flows round to the east of the Isle of Man (as indicated
also by the tides). In this last connection it is most
interesting to note that whereas the spring maximum of
the salinities is well marked at Stations V, YI, VII and
XI, between the Calf of Man and Holyhead, it is
practically undetectable at stations on the 54° of latitude
West of the Calf of Man. This probably means that
nearly all the water flowing through the Irish Sea passes
to the East of the Isle of Man. It is to he noted that in
my report for 1908, where I also referred to this last
point, there is an error in the third paragraph from the
bottom of the last page but one — “ the 34*0 isohaline on
the chart ” should read “ the dotted line on the chart.”

The curves of equal temperatures for the surface
water of the Irish Sea during 1909 have been drawn and
discussed by Mr. Johnstone, and are reproduced in the
plates illustrating his paper in the present report. These
isotherms show even more strikingly than the isohalines
the direction of flow of the water. In particular they
clearly show the current bending round to the East of the
Isle of Man.

SEA-FISIIERIES LABORATORY.

217

Fig, 22, Chart illustrating the probable directions of the currents in the Irish
Sea and Bristol Channel at the time when the Gulf Stream Drift is at a maximum.

218 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

EXPLANATION OE PLATES.

Plate II. Surface Salinities, February.

Figures to tlie Soiitli of the white line refer to the
period Feb. I-IO, 1905, unless there is a note to the
contrary.

Figures to the North of the white line, and West of
the line Calf of Man-Holyhead, have been communi-
cated to us by Mr. E. W. L. Holt, and refer to the
period Feb. 1-19, 1909. (A few figures referring to
1905 are also "specially indicated.)

Figures to the East of the line Calf of Man-Holyhead
are our own, and refer to the period Jan. 25-29, 1909.
The salinity, 34'43 at 52° 46' N. ; 5° 38' W. is that at
dl metres.

Plate III. Surface Salinities, May.

Figures to the South of the white line refer to the
period May I-I6, 1905, unless there is a note to the
contrary.

Figures to the North of the white line and West of
the line Calf of Man-Holyhead are Mr. Holt’s, and
refer to the period May 3-10, 1909. (A few figures
referring to 1905 are also specially indicated.)

Figures to the East of the line Calf of Man-Holyhead
are our own, and refer to the period May 17-19, 1909.

Plate IV. Surface Salinities, August.

Figures to the South of the white line refer to the
period Aug. 1-16, 1905, unless there is a note to the
contrary.

Figures to the North of the white line, and West of
the line Calf of Man-Holyhead, are Mr. Holt’s, and
refer to the period Aug. 2-10, 1909. (A few figures
lefeiring to 1905 are also sjjecially indicated.)

\

Plate H

S335 I ,
66 5504.

35 64

LB^UARY

55 84

55 12©

/54 45
.»5 ai\
'ei)

\C»rditan Bay.

Bristol Channel

©8SI6

©15 71

OiS 48

©55 46

•5515

(/■ai/t)

©554S

f©5S 35

©55-67

FRANCE

Surface Salinities, fe

PLATE m

Surface. Salinitie:

Dublin

FRANCE

■■i

!

ii;

J

i

i

r

’ 5,’.

P.':- ,

I

l:

%

. ‘iL

i

X,

SEA-FISHERIES LABORATORY.

219

Figures to the East of the line Calf of Man-Holyhead
are our own, and refer to the period July 26-28, 1909.
The figures for 54° 33^ N., 5° IT' W. and 54° 38' N.;

4° 56' W. refer to a depth of 18*3 metres,

Plate Y. Surface Salinities, November.

Figures to the South of the white line refer to the
period Nov. 3-22, 1905, unless there is a note to the
contrary.

Figures to the North of the white line, and West of
the line Calf of Man-Holyhead, are Mr. Holt’s, and
refer to the period Nov. 1-6, 1909. (A few figures
referring to 1905 are also specially indicated.)

Figures to the East of the line Calf of Man-Holyhead
are our own, and refer to the period Nov. 1-4, 1909.

In all the above plates the figures to the South of the
white line have been taken from Matthews’ reports
{loc. cit.). Figures used by Matthews in drawing his
isohalines are marked by a dot and circle. Figures given
in his tables, but not, apparently, utilised for the charts,
are marked by a dot alone.

A small underlined figure indicates that the station
is one at which samples from various depths are collected ;
the number in these cases is the number of the station in
the “ Bulletins trimestriels du Conseil permanent inter-
national pour I’exploration de la Mer.”

220 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

REPORT ON TEMPERATURE OBSERVATIONS IN
THE IRISH SEA DURING THE YEAR 1909.

By Jas. Johnstone.

The main results obtained from the periodic hydro*
graphic cruises made during 1909 are tabulated and
discussed by Dr. Bassett in a preceding Paper in this
Report, but I wish to give an account of the temperature
observations in particular, including data other than
those obtained in the course of the periodic cruises.
Special attention was directed towards obtaining a series
of records which might enable us to plot, with some i
probability, the course of the isothermal lines in the
eastern part of the Irish Sea. This part of the hydro-
graphic work was regarded as of considerable importance,
apart altogether from the question of the circulation of
water in the Irish Sea and St. George’s Channel, since it
is highly probable that the distribution and migrations
of some fishes are to be associated with the annual
temperature range on the various fishing grounds.

The Data. As in 1907 and 1908, copies of the semi-
diurnal temperature observations made from the principal
West Coast Light Vessels have been supplied by the i
Meteorological Office, and these are tabulated on page 245. ;

The observations made at 4 p.m. are alone considered. ,
Those from the Cardigan Bay Light Vessel are not j
included since they were discontinued in 1909. Monthly j
averages have been calculated. The latter have not been \
graphed in this Report.

The table immediately following that just mentioned
gives the temperatures of the sea at the surface at the
Hydrographic Stations. In addition to the quarterly
cruises a series of observations were also made at inter-

SEA-FISHERIES LABORATORY.

221

mediate times, except in December, when pressure of
other work prevented us from making the cruise. The
same stations, with one or two exceptions, were visited on
all these occasions; and not only were the usual observa-
tions made, but surface temperatures were also taken at
positions nearly intermediate to those of the regular
stations. These latter data are not tabulated, but they
are plotted in the series of sketch charts showing the
surface isotherms. As a general rule, Dichter thermo-
meters were used to take surface temperatures, but a
“ Kiel ’’ thermometer was employed at stations other than
the “ hydrographic ” ones. The error of this instrument
(about 0°T5 C.) was frequently determined , and its
readings are corrected. Deep temperatures were some-
times taken by means of a Kichter Eeversing thermo-
meter of the latest pattern, used on the Kansen-Pettersson
water-bottle frame. The readings of the latter instru-
ment always agreed with those of the Kansen deep-sea
thermometer used in the water-bottle, and in the end the
latter only was used; and this procedure seems to be
preferable as there must always be some degree of
uncertainty attached to the readings of a reversing
thermometer, no matter how perfectly made, when used
alone. The water-bottle was necessarily worked from the
windward side of the ship, the latter being brought into
position. Surface water samples for the determination of
temperatures were always taken from the leeward side :
this was the practice, though I do not suppose there
would have been a perceptible difference in temperature
on the two sides of the vessel.

In addition to data obtained in this way, I have also
considered observations made on board the ''James
Fletcher ” in the course of her ordinary patrol work. The
surface temperature is taken hourly when the vessel is at

222 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

sea, and the data thus obtained have been of the greatest
value. I give these (corrected) readings for a number of
coastal stations. It is, of course, evident that these data
cannot tell us very much concerning the circulation of
water, influenced as they are by proximity to the land.
It is, however, necessary that we should know the sea
temperature at coastal stations, when we attempt to
consider physical changes in the sea in relation to the
fishery periods, for it is near to the coast that some of the
most important local fishing grounds are situated. It
will be noticed that four of these coastal stations are
situated very closely to each other ; they are : — South
Stack, Carmel Head, Middle Mouse Island, and Pt. Lynas.
There are no fishing grounds adjacent to these parts of
the coast, but they are of importance since the North-
easterly drift of water in the Irish Sea appears to be
concentrated to the North and East of the Island of
Anglesey, and it was desired to record the temperature
hereabout with as much precision as possible. The
positions of most of these stations are indicated in the
chart on p. 223.

Hourly observations are also made on traverses across
Liverpool Bay, and across the Welsh Bays, but these are
not included in our published tables.

Our own observations are necessarily restricted to the
Eastern side of the Irish Sea, to the sea round the Isle of
Man, and to the Welsh bays, with the exceptions of
occasional incursions into Scottish waters. It has been
our privilege^ to be allowed to make use of the salinity
and temperature observations made by the Irish Depart-
ment of Agriculture and Technical Instruction, on the
Western side of the Irish Sea and in St. George’s
Channel, and without these data it would have been
* For which we are indebted to Mr. E. W. L. Holt.

SEA-FISHERIES LABORATORY.

223

Light

SHiPi

5ioF&ALLO>/AY ('

V. /-'LlGHT^.
Ship/

MORLCAMBEi
Bay ^

iumooD

mor^**cambe
bay lightship

'NELSON

BUOY

HORSE ,<
CH, ^0^

.RIDDLE

^ Mnitct

COLWYN

BAY

3CARNARVO!

H.Lak&

P

Fig. 23. Hydrographic stations in 1909.

224 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

impossible to draw the isotlierms, even those strictly
relating to Liverpool Bay.

Interpolation. It is quite necessary to interpolate
values for the surface temperatures, when drawing the
isotherms over a large area, since it is not generally
practicable to make the observations during a period of
time short enough to preclude the possibility of a change
of temperature. Even in the Western side of the Irish
Sea it has not been possible to visit all the stations
considered during the same cruise ; and it was not always
practicable to arrange that the cruises of the “ Helga ”
and the “James Fletcher” should be made during the
same days. Since the stations visited by the former vessel
are much more numerous, and cover a larger area than
the Lancashire ones, they have been taken as the basis
for the construction of the isotherms, and the observations
made on the English side of the Channel have been
reduced so that they represent the temperatures which
were, probably, characteristic of the sea during those
days on which the “ Helga ” made her observations. Just
how best to reduce these observations was a matter of
some little difficulty. I tried at first to make use of the
now well-known formula for interpolation suggested by
D’Arcy Thompson,* that is
f{{) = Aq -j- Ax sin {6 A 2 (sin 2 ^ C2) -f- &c.

In this expression the time is regarded as an angle,
the year being supposed to consist of 360 days, and the
temperature at any date is then a function of the sine of
the angle. Now if we had only four observations for the
whole year, these observations being made at the times
of the maximum, minimum, and half-amplitude, this
formula would afford the only possible means of inter-

* Report {Northern Area) on Fishery and Hydrographical Conditions
in the North Sea and adjacent waters. (1904-1905); Cd. [3358],
p. 186, 1907,

SEA-FISHERIES LABORATORY.

225

polating values for intermediate times, since, obviously,
manj^ curves could be drawn tlirougb the four given
points. It has, indeed, been shown* that such interpolated
values would really be very accurate. They would not take
account of the accidental ” variations in sea temperature
resulting from unusual winds, or the operation of other
factors, but would express only the generalised annual
temperature wave, which is indeed all that one attempts
in most discussions of such variations in regard to the
sea fisheries. It is assumed that the August sea tempera-
ture is that of the maximum, the February one that of
the minimum, and the May and November ones those
representing the half-amplitudes of the annual wave.
But whenever we have more than four observations, or
when, as in the present investigation, the date of the
cruises do not coincide with those times wdien we have
reason to suppose that maxima and minima occurred,
then the sine-function must be used cautiously in inter-
polation. The first Lancashire cruise had to be made at
the end of January, and the third at the end of July, and
we know, from other observations, that the actual
minimum fell in February and March, while the
maximum was in August. If, then, the above formula
had been employed, inaccurate results would have been
obtained, since the constants would have been incorrectly
deduced.

I have, therefore, resorted to graphic interpolation.
We have daily observations for the various light vessel
stations, so that a smooth curve drawn as closely as
possible to points representing the monthly mean tem-
peratures will give a very reliable picture of the annual
variations. The observations made at the Carnarvon Bay
light vessel are regarded as indicating the variation in

* Ibid. p. 186-8

226 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

temperature of the water of the Irish Sea unaffected by
the influence of the land. It is very probable that this is
the case, and that tlie water here has much more an
‘‘ open-sea ” character than in any part of the Irish Sea
North of the latitude of Anglesey. Conversely, the
Morecambe Bay and Liverpool North-west Light Ship
sea temperatures may be regarded as affected by the
influence of the land : those taken at the Bahama Bank
vessel are intermediate between the two series mentioned.
The Lancashire observations at stations 3, 4, 5, 6, 7, 11,
12, 13, 15, have therefore been corrected by just that
difference which is shown on the curve for the Carnarvon
Bay series, between the mean dates of Lancashire and
Irish cruises. The observations made at the other stations
have been similarly corrected from the Morecambe Bay
Light Vessel series.

The temperatures taken at the coastal stations have
been reduced to monthly means, and then smooth curves
have been drawn. In the case of most of these stations
the series is fairly complete, except in one or iwo months.
Values for these dates have been obtained graphically,
since interpolation formulae, such as those employed in
the evaluation of mathematical functions, cannot easily
be applied. The method of graphing a number of such
series suggested by D’Arcy Thompson^ is of the greatest
value, and has been employed in the present investigation.
A number of stations, which we have reason to believe are
associated together, inasmuch as the variations from one
to another are in the same direction, are grouped, and
the monthly temperature means are plotted to the same
axes of co-ordinates. Fig. 24 represents such a family
of curves, that for Bed Wharf Bay being taken as the
stamlanl one. The values of the ordinates for each of the

Ibid, p. 172.

SEA-FiSHERIES LABORATORY.

227

others change regularly by 1"^ C., as indicated in the
margin. The latter values have to be added or subtracted.
One is guided, in drawing the smooth curve, by the way
in which the adjacent ones run, and by using some
judgment, and having regard to what one knows of the

Fig. 24. Surface temperatures at various inshore stations in 1909.

physical conditions obtaining at each station. We see at
once that a good deal of confidence can be placed in these
curves, and that we may interpolate from them with a
reasonable expectation of accuracy. Such curves have
been made for all the coastal stations, and in drawing the

228 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

isotherms the temperatures for the mean dates in question
have generally been obtained from them.

Temperature Stratification.

There are no reasons for modification of the statement
made in last year’s Report that the Irish Sea is a
])ractically homothermic water mass, showing no
significant variation of temperature with depth. The
data relating to the hydrographic soundings are tabulated
in Dr. Bassett’s Report, and it will be seen that the
variations of temperature with depth of water are small
and inconstant. Such as they are, they appear to me to
depend entirely on (1) convection currents set up by the
chilling of the surface w^aters, and (2) lateral shore drifts
set up by winds, and by the relative differences in
temperature near and remote from the shore. It has been
pointed out that as the coastal water heats up in summer
at a greater rate than the off-shore w^ater, it must tend to
stand at a higher level, and thus off-shore currents or
drifts must be set up at the surface, wbile deep currents
set in towards the land to restore equilibrium. Obviously
these off- and on-shore drifts will be partiallv? or perhaps
entirely masked by the influence of the tidal streams.
Further, there is the strong effect of the latter in
conveying masses of heated or chilled water to and from
the shore. The Irish Sea and St. George’s Channel are a
relatively shallow water area, and the northerly drift
through this is too weak to set up notable temperature or
salinity, stratification. We find, then, that at stations 5, 6
and 7 the differences in temperature between surface and
bottom water never amounted to more than O' 7° C., and
were usually much less. The greatest differences detected
were at stations 1 to 4 during the J une cruise, during and
after a spell of fine weather. wRen the bottom water was

SEA-FISHERlES LABORATORY. 229

in one case 2’83° C. lower than that of the surface, and in
all fonr cases over 1° in amount. But the July cruise,
some six weeks later, disclosed very different conditions,
for t]ie mean difference then was less than 0’3° C. This
cruise was made after a week of rather exceptional
weather, when the wind had been blowing at times with
the force of a gale, the result being that the water over
the whole area investigated had become mixed up,
practically obliterating the differences previously
existing. This effect of a storm in relatively shallow
water has been pointed out by Krtinirne],* in the case of
the Baltic Station “ D Ostsee 7,” where, after an interval
of two days of stormy weather, the temperature difference
between surface and bottom had practically been reversed,
the mean remaining about the same. In the Irish Sea,
then, a spell of calm, warm weather leads to the heating
of the surface layers and the establishment of a condition
of spurious stratification. Significant vertical tempera-
tures are not to be detected anywhere betw^een Britain and
Ireland, as is shown by the numerous soundings made all
down the Channel by the “ Helga ” in 1909. Only in the
stations South from the Tuskar w^ere such disclosed. At
the Irish station, 51° 55' N, 6° 49' W, there was a
difference of nearly 5° C. at a depth of 64 m. and at 51^
22' N., 7° 0' W., a difference of 8'2° C. at a depth of 119 m.
This was in August. The soundings, during the same
cruise, in the fairway of the Channel between Mull of
Galloway and the Tuskar showed dift’erences of jus! the
same order as those we found between Calf of Man and
Holyhead at about the same time.

The Surface Temperatures in 1909.

At the minimum ; mean date, February 15th, 1909.
The surface temperatures are represented by the skotcJi

* Beteilig. Devtschlands a. d. Inlernat. Meeresforsch. Ill Jahresher.

Berlin, 1906, p. 19.

280 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY .

D

chart, fig. 25, p. 230. This has been plotted from our own
observations and from data supplied by Mr. Holt. The

SEA-FISHERIES LABORATORY.

231

courses of tlie isotherms in the region North-east from
the Isle of Man are rather conjectural, for there are no
observations with the exception of those from the Solway
Light Vessels. South-west from the Isle of Man the
observations are fairly numerous, and enable us to draw
the isotherms with some degree of accuracy ; while,
because of the greater uniformity of conditions in the
Channel between Ireland and the West coast of England
and the Isle of Man, the observations there, though fewer
in number, are still sufficient to determine the main
distribution of temperature. It is questionable whether
more numerous observations would make the task of
plotting the isotherms any easier. If we had a continuous
record of surface temperatures we should probably find
that minor irregularities would lead to dovetailing of the
contour lines, and the formation of islands ” of hotter
or colder water. The isotherms are to be regarded as of
the nature of smoothed curves, and probably represent
fairly the main facts of the distribution.

The warmest part of the area in February, 1909, was
that part of the Channel in the fairway between the
Tuskar-Bishops line, and the latitude of Anglesey; and
the surface temperatures there varied from about 8'5° to
9°. The coldest region was that extending from Air
Point, in Cheshire, to the mouth of Morecambe Bay ; over
the greater part of this area the temperature was less than
4°. The central part of the Irish Sea was characterised
by great uniformity, the variation being less than 1°. It
will be seen that the isotherms bend round to the North-
east of Anglesey rather sharply, and that the temperature
gradient is steepest here. If a line be drawn passing
through the isothermal lines where the curvature is
greatest, it will be seen that this would correspond verv
approximately to the axis of the Gulf Stream Drift, as

Fig. 26. Probable isotherms in the eastern part of the Irish Sea
on 20th March, 1909.

year as practically to obliterate any indications of the
further flow of water Northwards alonj’r the West coast
of England.

SEA-FISHERIES LABORATORY.

233

Marcli IGtli, 1909.

The data on this occasion are those of an inter-
mediate cruise, and there are no observations for the
Irish Sea to the West of the Calf-Holyhead line. But it
will be seen at once from fig. 2G, which represents the
isotherms at this date, that the main factor affecting the
distribution of temperature is the flow of water to the
?^orth-east. The mean temperature of the whole area of
sea to the East and South-east of the Isle of Man is very
much the same as it was in February, and that of the sea
immediately adjacent to the coasts of North Wales,
Cheshire and Lancashire is rather less than in the former
month. But the isotherms are now curved more sharply
into Liverpool Bay, towards which their axes are directed,
and just North from Bed Wharf Bay the gradient is very
steep. It will also be seen that there are now indications
of a flow of water to the North- v/est from the coast of
Lancashire, and also along the East side of the Isle of
Man. This latter drift is, however, comparatively feeble,
and the main drift of water from St. Georne’s Channel

O

appears to be to the East, round the coast of Anglesey,
and then to the North from the estuary of the Bibble.

M ay 6th, 1 909.

Fig. 27 represents the distribution of temperature
at the beginning of this month, and is constructed from
observations made over the entire area. There is greater
uniformity of conditions in this month than at any other
period of the year, and this is due to the fact that the
influence of the land is now exerted in the opposite
direction, as compared with the conditions in February
and March. The Gulf Stream Drift appears to have
attained its maximum development at the beginning of
this month, but the flow of water round Anglesey is not

‘234 TRANSACTlOxVS LlVfiHfOOL BIOLOGICAL SOClEtV.

Fig. 27. Probable isotherms in the Irish Sea and St. George’s
Channel on 6th May, 1909.

3'

SEA-FISHERIES LABORATORY.

235

so clearly indicated by the direction of the isotherms,
because the positions of the latter are affected by heating
up of the water oscillating towards and from the banks off
the Cheshire and Lancashire coasts. It is quite clear,
however, that there is now a general translation of warm
water from Liverpool Bay along the Lancashire coast, and
then to the North-west, and there are distinct indications
of the flow of this water round Point of Ayre, in the Isle
of Man, towards the North Channel. It is also clearly
evident, from this and the previous charts, that the
northerly drift of water from St. George's Channel
slackens at about the latitude of the Calf of Man, and
that the sea West and South from this point is a relatively
stagnant area. It is also apparent that South from the
Calf of Man, towards Holyhead, the water is rather
colder than in the fairway of the Channel, to the West,
and towards the West coast of England on the East.
There is the same increase of temperature, passing down
channel from Anglesey, as is indicated in the previous
charts.

June 16th, 1909.

The observations made in this month were those of
an intermediate cruise which, was extended into the North
Channel and Eirth of Clyde. The number of stations
which were investigated North from the Isle of Man were,
however, very few, and I have made no attempt at
drawing the isotherms further No.rth than adjacent to the
Isle of Man. The temperatures have been plotted in
fig. 28, and it will be seen that a very large part of the
Eastern half of the Irish Sea is now filled with relatively
warm water which is apparently drifting to the North-
west. In the charts representing the conditions in
February, March and May the isotherms were generally

SEA-FISHERIES LABORATORY.

237

convex towards tlie English coast : they are now convex
towards the North-west, except immediately to the Nortli
of Anglesey, where the prevalent drift to the North-east
is still indicated. During this cruise there was a marked
difference between the temperatures of surface and
bottom Avater, the former being significantly Avarmer, and
this is due, of course, to the heating effect of the sand-
banks along the Cheshire and Lancashire coasts.
Nevertheless, the direction of curvature of the isotherms
indicates that this heated Avater is gradually being
displaced to the North-west, passing round Point of Ayre
into the North Channel, and the direction of cuiwature of
the isotherms in the neighbourhood of Anglesey indicates
just as clearly that the cause of this displacement is the
continual entrance of colder water from St. Gieorge’s
Channel. It will also be seen that there are no longer any
indications of a flow of Avater immediately along the East
coast of the Isle of Man, the strength of the Gulf Stream
drift being now much less than in the Spring months.

August 4, 1909.

Eig. 29, which represents the distribution of surface
temperatures during part of this month, has been con-
structed from our own and Mr. Holt’s observations, and
includes the whole area. It represents A^ery nearly the
conditions during the period of annual maximum tem-
perature. The distribution is now entirely reversed, the
colder Avaters being those of the centre of the Irish Sea,
and in the fairway of St. George’s and North Channels,
while the Avarmest waters are those off' the coasts of
England and Wales. All the coastal waters Avithin the
territorial limits from Great Orme’s Head to the Solway
Firth are over 1G° in temperature, and tliough Ave ha\’e no

238 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

SEA-FISHERIES LABORATORY.

239

actual observations for tbis period of the year, it is
probable that temperatures of 17° to 18° characterise the
water in Tremadoc Bay. Bound the North Coast of
Anglesey the temperature is very little higher than that in
the fairway of the Channel, because the water of this part
of the coast is deep, and affected to a relatively slight
extent by the land, and also because of the continuous flow
round the promontory of Anglesey. It will be seen that a
large part of the Irish Sea South and West of the Isle of
Man is now filled with water which varies in temperature
from 12 0 to about 13°, and inside this is a smaller area,
the temperature of which appears to be a little greater.'
This warm island ” of water is established, no doubt,
because of the general deficiency of circulation in this part
of our area. In all the former charts this relatively
stagnant area was situated nearer to the Isle of Man, but
in August, when the strength of the Gulf Stream Drift is
nearly at its minimum value, the part of the Channel
covered by non-circulating water has increased greatly
in area. It should also be noticed that in these months,
when the Gulf Stream flow is weakest, the curving-in of
the isotherms towards Liverpool Bay occurs closer to the
Isle of Man than the Anglesey coast. When the flow is
strongest the water tends to pass closely round Anglesey.
Then, just as at the time of minimum temperature, the
isotherms in the eastern part of the Irish Sea run
approximately parallel to the coast line.

September 15th, 1909.

The observations at this time related to an inter-
mediate cruise, and only the eastern side of the Irish Sea
was investigated. The temperatures are again very
uniform, the greatest difference being only 1*65° The
Q

Fig. 30. Probable isotherms in the eastern part of the Irish Sea
on 15th September, 1909.

November 3, 1909.

The data are those collected during a quarterly cruise
and represent both our own and Mr. Holt’s observations.
The temperatures are plotted in fig. 31, and the isotherms
are drawn. With the exception of one or two indications
of “ islands/’ and what appears to be an unusually high

iii

SEA-FISHERIES LABORATORY.

241

sea-temperature to tlie North-west of the Isle of Man, the
distribution of warm and cold water appears to be quite
normal.

General Observations.

A study of the charts showing the approximate
courses of the isothermal lines during 1909 appears to me
to afford additional arguments in favour of the view of
the circulation of water in the Irish Sea, taken up by
Dr. Bassett in the preceding paper, that the general drift
of water, both at the surface and bottom, is from North
to South through St. George’s Channei, to the East close
to the coast of Anglesey, and then to the North-west
round Point of Ajre through the North Channel. This
view is supported both by the study of isohaline and
isothermal contour lines, and it will be seen that these
mutually confirm each other when we remember that each
series may vary independently of the other.

One sees quite clearly (I) that in St. George’s
Channel the isotherms, except so far as they run parallel
to the coast lines, are convex towards the North; and,
particularly in February and May, are bent over to the
East towards the coast of Anglesey, where the tempera-
ture gradient is steeper than on the Irish side; (2) that
this convexity of the isotherms is greatest to the North
and North-east of Anglesey, a condition again best
marked in February, March and May; and (3) that the
isotherms East of a line joining Calf of Man and
Holyhead are convex towards the English coast in the
southern part of the area, and convex towards the Isle of
Man in the northern part of the area. It is only in
September, when the temperature throughout is very
uniform, that this arrangement of the isotherms is
obscured.

242 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

%MULl
GALLOVJAy

Fig. 31. Probable isotherms in the Irish Sea and St. George’s Channel
on November 3rd, 1909.

SEA-FISHERIES LABORATORY.

243

It is also clear tliat all the indications point to the
main drift of water from St. George’s Channel, between
Isle of Man and Holyhead, and not between Isle of Man
and Ireland. 'No doubt some water may traverse the
latter part of the channel, but the directions of the
isotherms appear to me to indicate that the sea
immediately to the South and West of the Isle of Man is
characterised by a less strong circulation than is the case
nearer to the coast of North Wales.

Because of the relatively strong inflow round the

Fig. 32. Temperature gradient during certain traverses across
the Irish Sea from Morecambe Bay to Pt. Lynas.

coast of Anglesey, we find that the temperature range in
the sea ofl this part of the coast is less than that further
to the North along the Cheshire and Lancashire littoral.
The water in the Red Wharf Bay region is therefore
colder in the summer, and warmer in the winter, than
that of the inshore part of Liverpool Bay. One sees this
when studying the temperature variations whicli may be
observed while making passages from Fleetwood or Piel
to Point liynas. Fig. 32 represents the gradient on

244 TRANSACTIONS LIVERPOOL BIOLOGICAI. SOCIETY.

four such passages, two of which were made about the
time of the annual minimum of temperature, and two
about the time wdien the sea temperature was rising to the
maximum. The means were: — February 15, 5‘4°;

March 16, 5*06°; May 19, 9*4°; and June 25, 12-37°. In
February and March the temperature rises on the whole
during the passage from Morecambe Bay to Anglesey,
but in June and May it falls. The points on the diagram
represent the actual deviations from the means at each
spot on the line traversed when temperature observations
were made. I have drawn the curve smoothly through
the actual points, since it is likely that the temperature
change was a gradual and continuous one, and tliat the
observations themselves had no significant error.

This difference in sea temperature between Anglesey
and Morecambe Bay is due not only to the inflow of water
round the former island, but also to the great effect of the
extensive area of sandbanks in Morecambe Bay. On the
4th May, 1909, I made a series of observations of tem-
perature in the wnter of the shallow gutters and pools
left by the ebb-tide on the sands immediately to the North
and East of Eoa Island, in the Barrow Channel. The
lowest temperature was 14*2°, and the highest wns 17*2°.
At about the same time the water in the fairwav of
Barrow Channel varied from 8*5° to 8'9°, and outside, in
a line between the South end of Walney Island and
Fleetwood similar readings were taken. At the end of
July the temperature in the same place on the sands was
as high as 20*5°, while midway across the mouth of
Morecambe Bay it did not exceed 16°. It is quite evident
that the tidal stream surging backwards and forwards
over these sands must influence the temperature of the
water out from the land to a very considerable degree.

SEA-FISHERIES LABORATORY.

245

Sea-Temperatures at the Light Vessels, 1908-1909,
monthly means.

Carnarvon

Bay.

53°6'N.

4°45'W.

Liverpool

North-West.

53°31'N.

3°3FW.

Morecambe

Bay.

53°545N.

3°31'W.

Bahama

Bank.

54°20'N.

4°13'W.

Solway.

54°48'N.

3°32'W.

1908.

January ...

8 J

5-85

4-95

6-73

4-36

February...

7-2

5-5

5-05

6-33

5-16

March

6-83

5-73

5-1

5-85

5-23

April

7-2

6-66

5-5

7-00

6-83

May

8-65

9-6

10-0

9-3

10-95

June

, 10-85

12-8

12-76

11-83

14-26

July

12-6

15-95

15-7

1 15-0

14-95

August . . .

12-75

15-4

15-76

1 15-15

15-76

September

13-25

13-45

14-05

14-05

14-00

October ...

i 13-2

12-65

1 13-76

. 13-9

13-26

November

12-36

10-16

10-56

11-45

9-2

December

^ 11-05

6-26

, 8-2

1 1

8-33

5-8

1909.

January ...;

8-76

6-55

5-6

7-05

4-7

February

7-5

5-8

! 4-36

5-73 i

4-36

March |

7-4

5-1

3-86 I

5-23 1

3-95

April

7-7

7-23

6-73 !

7-33

6-36

May

9-6

10-4

9-6

9-7

10-05

June 1

11-16

12-6

12-26

12-26

13-9

July !

12-75

14-83

14-2 1

13-83

15-2

August ...

14-1 f

15-66

15-6

15-2 1

15-95

September

14-26

14-6

14-0 !

14-45

13-9

October ...

13-01

13-15

12-3 1

12-86 i

11-55

November

11-lil

9-25

8-7 i

9-86

7-05

December |

9-43

8-9

7-45

I

7-55

1

4-86

1

240 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Sea-Temperatures at the Surface at the Hydrographic Stations

in 1909.

Station.

Position.

25-29

19-21

17-19

14-18

26-28

14-16

1-4

Jan.

Mar.

May.

June.

July.

Sept.

Nov.

1

54°N.

3°30'W.

5-2

4-95

10-35

12-4

14-73

14-55

11-00

2

54°N.

3°47'W.

5-8

5-5

1

10-05

12-5

13-87

14-45

11-7

3

54°N.

4°4'W.

G-4 1

5-85

8-9

13-33

13-65

14-0

11-6 ,

4

54°N.

4°20'W.

7-7 '

5-75

8-9

11-73

12-95

13-6

11-47 ;

5

53°53'N

4°46'W.

8-3

6-6

8-53

10-62

12-45

12-9

11-57 ^

6

53°43'N.

4°44'W.

8-4

6-7

8-5

10-1

12-80

13-08

11-8 i

7

53°33'N.

4°41'W.

8-15 1

6-3

8-70

10-42

13-3

13-4

12-1 :

8

54^42^1^.

3°28'W.

5-3 I

5-5

9-3

12-05

15-15

14-15

11-25

9

54°9'N.

3°44'W.

5-9 i

5-65

9-05

12-55

14-15

14-15

11-25

10

54°13'N.

3°59'W.

6-0 I

51

8-95

12-75

13-75

13-95

9-95

11

53°56'N.

4°3PW.

*6-8

6-1

8-80

10-7

12-5

13-1

11-7

12

53°48'N.

4‘^13'W.

*6-1 ;

6-8

8-83

11-60

12-65

13-6

11-8

13

53°41'N.

3°55'W.

*5-65 i

6-8

9-1

13-82

13-75

14-35

11-5

14

53°31'N.
3°31 'W.

—

5-2

9-5

13-3

14-0

14-4

10-9

15

53°26'N.

4"5'W.

— i

5-65

1

9-3

12-05

14-0

13-95

—

* Positions on this cruise, with respect to these three stations, were

Illation 11, 53°54'N. ; 3°59'W.
„ 12, 53°47'N. ; 3°45^W.

., 13, 53°39'N. ; 3°30'W.

Sea-Temperatures at Coastal Stations, monthly means, 1908-9.

SEA-FISHERIES LABORATORY

247

•A-eg; u'eSip.T'c^
‘puGH Aun^ AV9|i^

0 oc 0 10 10 10 10 0 00

1 , 1 iCCOOOr^OOlipr-HlOCJil 1

1 1 1 1

*AV/91o^ ‘N.9SoSe

•A'cg u^Joipj-eQ
‘Aong saqo:;'eg

icvo o»oioto»oic lOiO

1 p 00 10 V- t;- CD 1 lOp 1 1

t^icl lAioiooAj^l loculi 1

\\S.,Lfof 'N.,LfoZQ
•punog Aaspj'eg

010 10 0 OC 0 1C 1— 1 »o 10 oc

I’YT' 1 1

1 4i ^ 2 ^ ^

’A\,£fof 'N.8To8S
q^^uog

C-— 1 oicccicocoiriicocs

10 F-F p p p p p 'ji >-H p csi 1 I

Goo:oiAoi£|irb'^'*<N 1 1

•M.98ot •N.tSoSe

•puajj pUI.l'BQ

lOiCC^iCt-ClOiCOiCiC
1 1 1 ippt^-ppF^pppiO'^i

1 1 1 IcDlCl^Ci^cb^^^GCcib

*A\/9Sot

•pu'B|si Gsnoj\[ GippiH

1C 0 IC 0 (M F-< 0 GO 10 1C 1C
. . 1 |C5SpiCpOCO<M^l:^COCt

1 1 1 IiciciAosf^co-^^iciocc

•AY Hot •N/9So€2
•s-euAg ^uioj

0 1C 0 1C 1C Cl 1C 1C 1C

1 1 1 1 t;- F^ p (C (M Tji <M 0

1 1 1 I'Cici^djF^cb^i'^coot^

•AV/jot -N/SSoSe
•A-eg

CO CiCOiCOOrf^lCiCiMiCiCiC
1 1 F^ p t;- p p p p p C t;- 0 p

1 dc'Coici^dic^coic-^'cccoGO

i-H f“H r— ( 1— ^ (— H

'AV/89o€ ’Ky\Zo29
) "p-Bag sauijQ

1C(MG001C1C'^1CIC1COC^

I 1 1 p p p p V- p P P p p p p

1 1 1 CO CO CO 05 M 4* 0 cb cib lA

1— "I 1— t 1— J F— ^ r-H

•AV.H08 -M.S8o89

•dBg [OodjaAig

ICIC ICICICICICICICICICICIC
,.— 05 — OOlCpCOCOF^I^*— icco 1

1 4 cb cb 4 cb 4 4 1C 1C 4 cb 05 1

i

•M/SI08 ‘M/Stogfi
i "Aong uosjajsj;

1C ICICICICICICICICICICICIC
1 |1C ppppppF^pt-CX)iC05

1 l4 4cbcbi4ocbiccbcbc^i4ic

•AYS08 •N.OSoSS
t -punoj^ podi[o'B[g

iCiC 1C ICXIC ICICICIC

— pp pp-^'^pppppppp

cbic4 44cbi4oi:biccbcbcii4io

•AY9o8 'N.6So8e
1 ’^^g aqui'Boaiox\[

1

1C 0 1C iC 1C CJ Cl IC 1C 1C 1C

p it- pp — p'^pt;-pO5iC05 1

c 14 ic44i4d5M4^cb(:^cib 1

•A\.STo8 ‘NJotfi
1 -Aong s-BO [aig

i

1C 1C 1C 0 »c 1C >: ic ic 1C 1C

ipic ptpppppp'i<ppcc 1

1m4 ic44iAcb — 4^mm65 i

Position

of

Station.

1908.

August . . .
September
October ...

1909.

January ...
February

March

April

May

June

July

August . . .
September
October ...
November
December

'igures in italics represent interpolated values.

248 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

NOTE ON THE ELOOKBURGH COCKLE BEDS.

By Andrew Scott, A.L.S.

The Rev. J. Eowler, V icar of Cark-in-Cartmel, who
takes a very great interest in the welfare of the Elookburgh
fisherman, wrote to Mr. Mnspratt a short time ago drawing
his attention to the deplorable condition of the cockle beds
at Elookburgh, and pointed out that for the first ten months
of 1909 only 439 tons were dispatched, as against 1,647
tons in 1907 and 1,330 in 1908. On January 6th Mr.
Muspratt wrote asking me to communicate with Mr.
Eowler and arrange to inspect the beds at an early date.
Special enquiries as to the damage likely to be caused to
the beds by the black headed gulls, and whether the number
of these birds have increased materially of late were to be
made. The weather of January proved very unfavourable
for a careful inspection of the extensive area worked by
the Elookburgh men, but as this report had to be sent in
some days previous to the meeting of the Scientific Sub-
Committee on Eebruary 9th there was no time to wait for
favourable days. Two visits were made, viz., on January
17th and January 26th. On the first date a N.W. gale
accompanied by heavy rain showers had to be faced. The
second visit was made during the intense frost that followed
the snowstorm of January 22nd. Although the weather
was unfavourable and the gulls much less numerous than
they would have been under more satisfactory conditions,
there was every evidence that they are very destructive to
the growing cockles. On the first visit 1 watched a flock
of about 50 birds feeding. 1 then examined the ground
and the excreta. The freshly evacuated excreta was very
pleniiful considering the number of birds in the flock and
proved that they had been feeding actively. Practically

SEA-FISHERIES LABORATORY.

249

tlie whole of tlie exoreta of these birds was composed of
pure crushed shells of one and two year old cockles. In a
few^ cases the fragments of cockle shells were mixed with
crushed shells of “ Henpens ” {Tellina haltJiica). Excreta
consisting of pure Henpen ” shells was only observed in
two instances. In the interval between the visits, a good
deal of shooting had been done and it was impossible to
get close to the gulls which were much more numerous
than before, and were scattered in flocks all over the sands.
The excreta again consisted of little else than the crushed
shells of cockles. The gulls that I watched feeding simply
picked the cockles directly out of the sand, but the fisher-
men state that they have frequently seen them tread the
sand with their webbed feet with a similar effect to the use
of the Jumbo only on a smaller scale. The birds then
eat the cockles brought to the surface. The fishermen say
that the adoption of a close time for gulls under the Wild
Birds Protection Acts has led to a vast increase in the
number of birds produced each year, they are becoming
less afraid of man, and are the chief cause of the decreasing
yield of cockles at Elookburgh. From the observations I
made, I saw that the gulls follow the track of the “ Jumbo
pretty much as they follow the plough on land and eat the
cockles that remain at the surface. The Eev. J. Fowler,
who has lived at Cark for 13 years, says there has been an
extraordinary increase in the number of gulls in his ex-
perience. He has frequently seen many thousands of
these birds feeding on the sands, and within recent years
two gulleries have become established on Holker Mosses,
between Cark and Haverthwaite. Dr. Jenkins in his
report for the Quarter ending December, 1904, gives a
chart of Morecambe Bay showing the cockle beds and the
gulleries. He made a personal visit to the beds and agreed
with the statements made in previous Quarterly Deports

250 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

as to tlie destructive action of the g“ulls. The chart shows
three gulleries, viz., The South End of Walney Island,
Cockerham and Wyresdale. Mr. Fowler informs me that
he knows of three additional places, viz., Ravenglass, and
the two on Holker Mosses.

If the noteworthy decrease in the value of the shell-
fish industry had been limited to Flookburgh, one would
have had no difficultj^ in coming to the conclusion that
gulls were mainly responsible for it. Unfortunately,
however, on comparing the money value of the shell-fish
landed at the Lancashire ports during the last four years,
as given in the December reports drawn up for the Com-
mittee, one finds that there has been a general decrease in
the money value of the Lancashire shell-hsh industry from
1908. The value of the shell-fish landed at the Lancashire
ports in 1907 showed a net increase of £5,117, compared
with the value in 1906. This gain was made up by an
increase of £2,645 at Morecambe, and £1,558 at Cark.
Southport, Fleetwood and the Lune Estuary contributed
practically the remainder of the gain. The money value in
1908 showed a net decrease of £4,098. The loss of fully
half of this sum occurred at Southport. Lytham, Fleet-
wood, Morecambe and Cark divided the remainder of the
loss. In 1909 a further net decrease of £4,447 took place.
Morecambe suffered to the extent of £2,158. Cark and
Southport lost practically £1,382 each. Out of the nine
Lancashire ports only two showed any increase over 1908.
Fleetwood improved by £917 and Barrow District by £99.
The general decrease in the money value of the Lancashire
shell-hsh industry especially during 1909 is not due
entirely to the destruction brought about by gulls.

All shell-fish beds have many natural enemies. Plaice
and hounders feed vigorously upon small mussels and
cockles. We generally hnd when hat hsh are plentiful

SEA-FISHERIES LABORATORY.

251

near the shore during the summer and autumn, that they
have been attracted by the abundance of small shell-fish.
The common starfish or crossfish soon destroy a mussel
bed once they settle upon it. Giulls, as we know, help very
considerably to destroy young cockles. They have doubt-
less done so from very early days, and if unchecked can
cause great local destruction.

The chief cause of the fluctuation of the flsheries for
shell-fish along the Lancashire coast is due to natural
influences. vSome marine animals are more susceptible
than others to the climatic changes that are always going
on around us, and naturally suffer from a sudden rise or
fall of the temperature of the sea. The eggs produced by
a spawning cockle are fewer in number than is the case
with the mussel, and spawning takes place in the early
spring. The spat from the bed of cockles may, therefore,
be completely destroyed by the sea water becoming
suddenly cooled as it flows over the surface of very cold
sands. A whole year will elapse before another production of
spat will take place. An intense frost will kill large numbers
of cockles wherever its influence is felt. In the winter of
1894-5 the whole of the Lancashire coast line was covered
with ice-floes for a considerable time and many hundreds
of tons of dead cockles were washed up by the first gale
after the frost had disappeared. The extreme cold of that
winter had a marked effect on the fishery at Flookburgh
and the total quantity of shell-fish sent off during 1895
was only 743 tons. The beds may become sanded up by
heavy seas washing over them, or through the shifting of
the numerous channels, and the shell-fish are smothered.

Over-fishing may also occasionally take place, and it
is a well known fact that some beds take longer than others
to produce marketable shell-fish once they ' have been
depleted. The fisherman to his own advantage ought to

252 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

take great care of tlie undersized sliell-fish, because after
all these are the hope for the future. The small cockles
for instance that pass through the riddle ought not to be
left in heaps to shift for themselves. They ought tc be
spread out a little and lightly forced back into the sand.
If the heaps are simply left untouched they are exposed to
the attacks of the gulls, the frost of winter, or the warm
sun of the summer, and none of these influences are "ood
for the welfare of a cockle bed. A female cockle begins
to produce spat when it is between two and three years of
age and it is at this period that it becomes marketable. It
therefore follows that if large quantities of cockles which
just fail to pass through the legal riddle are taken away
between the autumn of one year and the spring of the next,
the repopulation of a bed by a fresh supply of young will
be greatly retarded.

The present condition of the cockle industry at Flook-
burgh is unsatisfactory and young cockles are very scarce.
One bag of marketable cockles per man each tide is all
that is being obtained. The suggestions given by Dr.
Jenkins in his Quarterly Deports ending December, 1904
and 1905, afford the best solutions to counteract the present
decrease in the population of the Flookburgh beds. They
are («) Advice to the fishermen not to sell on commission ;
(b) The exemption of gulls from the provision of ‘‘ The
Wild Birds Protection Act.” ; (c) Eestriction of the use
of the “ J umbo ” to a minimum, or even its total abolition.
A reduction in the number of gulls could easily be brought
about by destroying the eggs in the nesting season. I do
not think the total abolition of the “ Jumbo ” would be
regarded as a hardship by the fishermen as some of them
that I met at Flookburgh voluntarily suggested it, stating
that many cockles brought up to the surface by its use are
not marketable. Care should also be taken to spread the

SEA-FISHERIES LABORATORY.

253

small cockles that pass through the riddle, and press them
into the sand. If a supply of small cockles can be secured
in the spring an attempt should be made to restock parts
of the Flookburgh area.

The following table gives the amount, in tons, of shell-
fish sent off by rail from Cark Station during the last
twenty-eight years. The figures, with the exception of
those for 1908 and 1909, have been taken from the notes by
Mr. W. R. ^lash, Cartmel District Weather and Farming
Notes.” The Lancashire Sea Fisheries Committee was not
in existence during the first eight years of this period and
in the twenty years that have elapsed since its institution
the quantity of shell-fish sent away from Cark Station
each year has only once been less than the quantity dis-
patched in 1886.

Year.

Tons. .

Year.

Tons.

1882

2,827

1896

930

1883

2,665

1897

2,011

1884

1,177

1898

1,797

1885

861

1899

1,286

1886

662

1900

1,059

1887

1,040 ‘

1901

1,250

1888

1,616

1902

1,232

1889

2,488

1903

885

1890

3,161

1904

770

1891

2,749

1905

394

1892

1,684

1906

1,009

1893

1,336

1907

1,647

1894

1,218

1908

1,374

1895

743

1909

718

The majority of the cockles dispatched from Flook-
burgh find their way into the cotton districts of Lancashire,
and when any disturbance takes place in the cotton trade,
either through scarcity of work or lock-outs, it is said

254 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

that the demand for cockles falls otf. Mr. W. E. Xash in
his monthly notes for 1908 on the sand fishery at
riookbiirgh, makes the following remarks : “ Owing to
the impoverished condition of so many cotton workers and
traders, and others dependent upon them for a living, the
demand for cockles has fallen off very much, and during
several weeks double the quantity actually sent could
have been supplied had there been any demand.” The
quantity of shell-fish sent away from Cark in 1908 shows
a reduction of 273 tons when compared with 1907. Some
of this reduction at any rate was probably due to the
depression in the cotton trade in 1908.

SEA-FISHERIES LABORATORY.

255

AN INTENSIVE STUDY OF THE MARINE
PLANKTON AROUND THE SOUTH END OF
THE ISLE OF MAN.- PART III.

By W. a. Herdman, F.R.S., Andrew Scott, A.L.S., and
W. J. Dakin, M.Sc.

[Explanatory Note. — Tlie work was carried on in
1909 very miicli on the same lines as in the two previous
years. The same localities were fished, and the same nets
were used, with the addition of a few improved forms to
he discussed below. Mr. W. Riddell again gave most
efficient help in the operations at sea, and Mr. Scott and
I have divided the work of preparing this report in
exactly the manner that was stated in last year’s Intro-
ductory Note. Mr. W. J. Dakin (now Demonstrator of
Zoology in the University of Belfast), while working at
Port Erin as 1851 ” Exhibitioner in Zoology of the
I^niversity of Liverpool, in April, 1909, took entire charge
of our hydrographic observations at sea, and of the
subsequent working up of these in the laboratory. When
I had to return to Liverpool, in May, Mr. Dakin continued
both the planktonic and the hydrographic observations
with some of our nets and instruments, but according to
a modified scheme, taking samples twice a week during
the greater part of the summer. As this portion of the
work, although planned under my direction, was carried
out wholly by Mr. Dakin, Mr. Scott and I invited him to
join us as part-author of this report, and consequently the
section on hydrographic results has been drawn up by
Mr. Dakin, and he has also helped me in some of the other
sections.

R

256 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

We are indebted to Mr. Chadwick for much hel]) at
the Port Erin Biological Station; lo Mr. Riddell for his
assistance in the Liverpool Laboratory in analysing,
comparing and discussing the results of the many hauls
taken during the year; and to Miss Lewis for the
numerous statistical lists, tables of occurrence and (uirves
which she has drawn up. Mr. Riddell and Miss Lewis
have been most helpful during the writing out of this
report, and have saved me much time by preparing
the material for me to consider and discuss. —
W. A. He RDM AN.]

INTRODUCTION.

W^e shall first under this heading give an account of
how the work was carried out in 1909. Then will follow
a section on the hydrographic conditions off Port Erin.
Finally, the planktonic results will be discussed in detail.

The Material Available.

The collections made this year have been more
numerous than in either of the previous years, but for the
most part fall into the same series of samples, and are
therefore directly comparable with those of ’07 and ’08.
The total number of samples now examined in this
intensive study of a small marine area is nearly 2,000,
made up as follows : —

Year.

At Sea, from Yacht.
Spring. , Autumn.

In Bay
throughout
Year.

1 Mr. Dakin’s
hauls.

Totals.

i

1907

218

279

138

1 635

1908

156

242

157

555

1909

329

147

231

49

756

Totals

703

668

526 1

i

+ 49 !

1

1,946

SEA-FISHERIES LABORATORY.

257

It will he seen, moreover, that each of the three years,
and each of the three vertical columns, is represented hv
a suhstantial niimher of gatherings, and that these
numhers are fairly equal, lying as all six do between 520
and 756.

Of the total numher fl,946) of samples, a small pro-
portion (73) were taken with larger nets — the shear, the
Yngel and the large Nansen — which cannot he regarded
as comparable with the rest. The shear appears to catch
about 15 times as much as an ordinary small tow-net, and
the large Nansen (100 cm. in diameter of mouth) about
10 times as much. The Yngel has at least the same
catching power as the shear net. Of the remainder, 511
are hauls taken with vertical closing nets (Hensen and
Nansen), not ver}^ different in size and catching power
from the ordinary tow-nets of 14| inches diameter of ring,
with which the other 1,362 samples were obtained. Of
course individual nets differed somewhat in their catches
according to the shape and make, but when seven of them
(“ Hensen,” Nansen,” “ Weight,” “ Otter,” Coarse,”
“ New,” and “ Old ”) were used simultaneously day after
day, we believe a useful roughly approximate idea of the
proportional variations in the plankton can be obtained by
averaging the hauls so as to get a single figure per net for
each locality (see below, pp. 345-349).

Outline of the Year’s Work.

Throughout the year, from January 1st, 1909, to
December 29th, Mr. Chadwick took official ” gatherings
across Port Erin Bay, generally twice a week, and some-
times more frequently. The S.Y. Ladybird ” (fig 1) was
fitted out for the season towards the end of March, and
her first plankton trip was on March 27th. From that

258 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

time lo A[)ril 26tli she was constantly engaged in this
work, and obtained d2h colleidions on 2d working days.
During that period we have tlie yacht gatherings taken
at various stations (see fig. 2) out at sea (up to 12 miles
N.W. of Bradda Head), and also the “ official ” gatherings
taken across the Bay. After April, Mr. Dakin, from a

Fig. 1. — S.Y. “ Ladybird ” on a Plankton cruise at Easter, 1908.
From a photo by Edwin Thompson.

small sail-boat, continued the work at sea in a modified
form from May 3rd to July 1st inclusive. The
‘‘ Ladybird ’ took collections again almost daily from
August 3rd to 11th (14 1 gatherings in 8 working days).
After that date we have only the official gatherings in the
Bay up to the end of the year.

SEA-FISHERIES LABORATORY .

259

Methods and Equipment.

Tlie methods of work were practically the same as iji
the previous two years. It may be useful to repeat here
the same little map that was used last year in order to
show the localities at which the gatherings were taken.
The nets used throughout the three years have been:- -
Two closing vertical nets, the Nansen and the Petersen-

Hensen, a weighted and two surface, open, horizontal
tow-nets, all made of No. 20 bolting silk; and, in addition,
some coarser silk tow-nets (Nos. 3, 6 and 9 silk) and the
larger-meshed shear-net and Yngel trawl.

In the equipment for the present year, while keeping
the older nets for the sake of continuity and comparison,
some new ones were added, viz., a large Nansen, 100 cm.
in diameter of No. 3 silk; and a series of ‘M'unnel ” neis
ffig. 3) which will be referred to again below, one of them

260 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

being attaclied to a small otter-board worked from the
ship’s side far forward for comparison with the others ai
the stern.

The yacht was furnished with a small “Lucas”
sounding machine, having 400 faths. of steel piano wire,
wliich has been found to be of service in giving rapid and

Fig. 3.—“ Hensen,” “ Nansen,” “ Funnel ” and “ Open ” Plankton
nets on “ Ladybird.” From a photo by Edwin Thompson.

accurate soundings, and for the water-bottle and ther-
mometer in the hydrographic work, and also on occasions
for taking vertical hauls with the Xansen net (fig. 4).

We have also added to the equipment for the
hydrographic work an Ekman Water-bottle provided with
liichter's thermometers and, for occasional work, the
lighter lluchanan-liichard (or “Monaco”) Water-bottle
(hg. 5) as used on the Prince of Monaco’s scientific yacht
“ Princesse Alice.’’

SEA-FISHERIES LABORATORl*.

261

Fig. 4. — Lucas Sounding Machine, as used with Nansen
vertical closing net on “ Ladybird.”

Fig. 5. — The
“Monaco” Water-
bottle ; on the
right descending
open, on the left as-
cending closed. The
messenger (on the
line) which strikes
the lever, raises the
pin and so allows
the brass bottle to
reverse and close
itself, is seen in each
case at the top of
the figure. The two
projecting sockets
are for the reception
of a thermometer
which reverses with
the water-bottle.

262 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

IIYDROGEAPIIIC CONDITIONS OFF POUT ERIN
IN APRIL TO JUNE (Drawn up by W. J. Dakin).

This IS an account of the hydrographical observations
made in conjunction with the plankton work carried on
by Professor Ilerdman in A})iil, and of those made in
May and Juin^ whilst taking plankton samples myself.
I he former, which are in greater detail, were carried out
on the steam yacht “Ladybird,” the latter on a small
sailing boat. I have dealt chiefly with the temperature
and salinity of the water, but some oxygen determinations
were also made during April. In order to discuss
differences in catches of nets at different times and
places, it is necessary to know the prevailing conditions
of environment affecting the plankton, at those places.
The observations are confined practically to two stations
(I and III). They have, however, been very numerous
and probably such an intensive study at stations isolated
from the larger land masses is of rare occurrence.

Much of the German quantitative plankton research
has been carried out on the Baltic Sea, where the
hydrographic conditions are most varied and interesting,
but may, I think, lead to rather one-sided views. It is
quite obvious, for example, that if the surface salinity is
only 18 and that of the bottom water is 26
it will make a marked difference in the plankton. It
seems natural under such circumstances to correlate
changes in plankton with changes in the hydrographical
conditions.

ffhese gieat changes, however, may completely mask
other smaller variations which exist in places where the
salinities and temperatures are approximately alike. It
is undei these latter conditions that plankton problems
must be attacked in the Irish Sea, which is, as far as

SEA-FISHERIES LABORATORY.

263

affects the plankton, practically a lioinothermic and
homosaline water mass.

Temperatures in April.

The surface temperatures have been taken with
Kichter thermometers divided into To°C. and provided
with Charlottenberg certiffcates. The correction has been
applied in all cases. The deeper temperatures have been
taken with a Eichter reversing thermometer attached to
an Eknian Water-bottle. Tbvo thermometers should be
used, or temperatures be taken twice at the same depth
(and not in succession), in order to check the readings,
since the best reversing thermometers may at times
})rove fickle. For comparison there exist at present only
some records taken in recent years by Mr. Johnstone on
board the “ James Fletcher ” at two stations not far from
the Isle of Man, and a few taken by Mr. Drew on the
“ Ladybird ” during the summer of M8 at our two
Stats., I and III, lying 5 miles and 2 to 3 miles outside
of Bradda Head, respectivelju

Stat. I. 5 miles N.W. Bradda — Corrected temperatures.

Depth —

5

April.

6

7

8

9

13

14

0 fathoms

7-10

7*22

7-52

8-15

7-92

7-42

7-62

5 „

—

—

—

7*62

7-27

10

7*82?

7-62?

712

7-18

7-12

7-43

15 ,,

—

—

—

—

7-23

20

7-82?

7-87?

7-22

7-19

7-17

7-42

25

—

—

7-22

7-37

15

19

21

23

24

26

0 fathoms

5 „

7*77

.... 7*57

7-62

7-52

7-48

7-48

7-48

7-57'

7-64

7-72

8-12

10 „

.... 7-39

7-52

7-65

7-67

7-67

7-78

7-78

7-76

15

.... 7*35

20 „

7-30

25 „

.... 7-32

264 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Stat. III. •) miles N.N.W. Hradda— Corrected temjieratiires.

April.

Jleptli.

5 0 <) 13 14 IT)

0 fathoms 6-37 (v92 9-52 7-42 7-02 7-84

5 „ _ _ _ 7.47 7.07

10 „ 7-02? 7-47? 6-82 _ _ _

15 „ 7-10? 7*58? — 7-17 7-37 7-37

20 „ — — 7-10 _ _ _

17 19 23 24 2(>

0 fathoms 7-72 7-80 7-92 7-92 8-17

5 7-(34 7-(>9 — 7-70 S-07

10 „ — -- — 74>7 7-82

15 „ 7-52 7-47 — 7-05 7-75

It will be seen that at both stations there bas been a
steady and slow increase in the temperature tliroughout
the month, with one exception, on the 8th and 9th, when
an abnormal rise was noted, which fell during the
following days to the normal. The curves are, however,
not much broken up — that is, the minor temperature
variations referred to by Johnstone^' have not been of
great magnitude, nor of frequent occurrence. This is
probably due to the isolated position of the Isle of Man
and the freedom from such disturbances as are caused by
a rising tide passing over heated sandbanks.

It will be seen that the change noted on the 8th and
9th is of far greater magnitude at Stat. Ill, near the land,
than at the 5-mile station, and in fact the coldest and
warmest surface temperatures were observed at the
in-shore station. During January, February and,
perhaps, March the lowest temperatures will be at
Stat. Ill, wliilst in April and the following months the
temperature will be on the average slightly higher (as the
tables for April indicate), but a succession of abnormally

* Lancashire Sea-Fisheries Lai)oratory Report, p. 73, 1908.

SEA-FISIIERIES LABORATORY.

265

warm days in February or March would quickly affect
the water at Stat. Ill, and similarly a sudden fall in
April, reversing these conditions. The great rise that
has been referred to above and also its ehect on the
vertical distribution of temperatures can be traced quite
easily to the weather conditions. After a prolonged
})eriod of cold weather with a steady thermometer, there
followed three or four abnormally fine and hot days (the
temperature of the air only reached that attained at that
time on about five days between then and July 16th).
From the 6th to the 9th the sea w^as calm, there was
practically no wind, and continuous sunshine prevailed
during the day. The result was a very considerable
beating of surface water, the deeper water, however,
remaining unaffected. The minor increase on the 15th
was due to a similar though less marked cause.

Vertical Distribution of Temperature.

These records, though taken in shallow waters, with
the exception of one series made in water of over 60 faths.,
are not without interest, and seem to support the view
that the Irish Sea is practically a homothermic water
mass, though Johnstone states fhat in 60 cases the bottom
water was coldest, in three cases was warmest, and in
three cases was the same as the surface*

My records are as follows : — From April 8th onwards
10 series were taken at Stat. I, 9 series at Stat. Ill, and
1 at Stat. A in deep water. In every case the bottom water
was colder than the surface water, but by very small
amounts. In all cases but four the difference between
surface and bottom water was less than half a degree.
These four cases occurred on the 8th and 9th of April.
The differences between surface and bottom were 0*96° 0.,
0*75° C., 2A2° C., and 0*56° C. The greatest of these
differences is less than those observed by Drew on the

266 TKANSACTIONS LlVEllFOOL BIOLOGICAL SOCILTV.

Ladybird ’ in tlie summer of ’08, and all may be
explained b^' the abnormal heating of the surface water,
as can be readily seen from the curves. If the 10 fath.
temperature be compared in those four series with the
bottom (20 faths. in three cases and 60 faths. in the other)
the dilferences are only 0'01° C., 0 05° C., 0‘28° C., and
0‘d2° C. respectively. Thus, where the dift'erence was so
great as 2 42° C. between the surface and the bottom, a
ditference of 2 14° C. existed between the surface water
and that at 10 faths., plainly due to the heating effects of
the sun. I find, therefore, no great difference betw*een
surface and bottom water, always less than half a degree
except on abnormal occasions, and a difference of over
2° C. can be produced solely by the action of the sun’s
rays on the surface water. Such small differences can
scarcely be used as evidence for the inflow of colder
currents from without, and I imagine will exercise no
perceptible influence upon the vertical distribution of
planktonic organisms.

Salinities in April.

The samples of sea-water examined were taken with
the Ekman Water-bottle, at the same time as the
temperatures. The remarks made with regard to the
frequency of the determinations of temperature apply,
therefore, with equal force here, though the temperatures
will naturally vary and be affected by weather conditions
to a greater extent than the salinity. The salinities have
been determined by titrations of chlorine by Mohr’s
method, using the Knud sen apparatus and referring the
results to standard sea- water. The salinities, etc., were
then calculated by means of Knudsen’s . hydrographic
fables. T° is the femperature (Centigrade) of the water
in situ. Cl %o is the amount of chlorine per 1,000 parts of
water, and S%o is the salinity.

SEA-FISTIEEIES LAEORATORY.

267

Stat. 1. 5 miles N.W. Bradda.

Date.

Depth in
fathoms.

rpo

Cl 7oo

/oo

April 5...

0

7-10

18-98

34-29

„ 5...

10

—

18-95

34-23

„ 5...

20

—

18-97

34-27

„ 6...

0

7-22

19-00

34-33

„ 6...

10

—

18-98

34-29

„ 7...

0

7-52

18-94

34-22

„ 8...

0

8-15

18-96

34-25

„ 9...

0

7-92

18-92

34-18

„ 9...

10

7-12

18-93

34-20

„ 9...

20

7-17

18-98

34-29

„ 13...

0

7-42

18-86

34-07

„ 13...

15

7-23

18-90

34-14

„ 13...

25

7-22

18-90

34-14

„ 14...

0

7-62

18-92

34-18

„ 14...

15

7-43

18-89

34-13

„ 14...

30

7-37

18-90

34-14

„ 15...

0

7-77

18-89

34-13

,, 15...

10

7-39

18-91

34-16

„ 15...

30

7-32

18-92

34-18

„ 19...

0

7-62

18-88

34-11

„ 19...

10

7-48

18-91

34-16

„ 19...

15

7-48

18-92

34-18

„ 19...

20

7*48

18-9]

34-16

„ 21...

0

7-57

18-84

34-04

„ 21...

10

7-52

18-85

34-05

„ 21...

20

7-30

18-93

34-20

„ 23...

0

7-64

18-91

34-16

„ 23

10

—

18-91

34-16

„ 23...

15

—

18-91

34-16

„ 23...

20

—

18-90

34-14

„ 24...

0

7-72

18-91

34-16

„ 24...

10

7-65

18-91

34-16

„ 24...

15

7-67

18-92

34-18

„ 24...

20

7-67

18-91

34-16

„ 26...

0

8-12

18-91

34-16

„ 26...

10

7-78

18-92

34-18

„ 26...

15

7-78

18-93

34-20

„ 26...

20

7-76

18-92

34-18

268 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Slat. III. 2 to 2) miles oiitsirle Hrndda.

Date.

Depth in
fathoms.

TO

Cl 7oo

8 7

ICC

April

5..

0

6-37

18-99

.34-31

99

5..

10

—

18-96

34-25

„

6...

0

6*92

18-91

34-16

99

6...

10

—

18-93

34-20

”

9...

0

9-52

18-87

34-09

13...

0

7-42

18-83

,34-02

99

13...

15

7-17

18-89

34-13

,,

14...

0

7-62

18-86

34-07

14...

15

7-37

18-87

34-09

,,

15...

0

7-84

18-91

.34-16

15...

5

7-67

18-87

34-09

15...

15

7-37

18-89

34-13

,,

16...

0

7*8

18-92

34-18

_ ”

16...

20

—

18-92

.34-18

,,

19...

0

7-80

18-90

.34-14

,,

19...

5

7-69

18-86

34-07

19...

15

7-47

18-90

34-14

23...

0

7-92

18-93

34-20

„

23...

5

—

18-91

.34-16

„

23...

10

—

18-91

34-16

23...

15

—

18-92

34-18

Stat. A.

Id miles N.W. Bradda.

Date.

Depth in

Cl 7oo

S7„„

fathoms.

/ oo

April

7...

0

—

18-90

34-14

7...

20

• —

18-88

34-11

7...

30

—

18-93

34-20

7...

40

—

19-03

.34-38

7...

50

—

19-04

34-40

_ ”

7...

60

—

19-03

34-38

99

8...

0

7-85

18-85

34-05

99

8...

5

7-04

18-83

34-02

99

8...

10

7-00

18-85

34-05

„

8...

20

7*07

18-86

34-07

99

8...

30

7-17

18-91

34-16

,,

8...

40

7*20

18-98

34-29

8...

60

7-32

‘ 19-03

34-38

SEA-FTSITEKTES LABORATOEY.

269

On the whole, these results will he seen to agree with
those of Bassett,* which have been carried ont over a more
extended area. In 14 cases ont of 21 series the difference
betw^een the surface and bottom is 0*05 7oo<^i' less, and since
the experimental error may be 0'02°/oo> it will be seen that
the actual difference between surface and bottom water
is but small. In 8 cases it is only 0 02°/oo ei* less. The
greatest differences, as might be expected, are at the deep
Stat. A in mid-channel, and are 0*24 %o 7oo

respectively. In seven cases the surface is more salt than
the bottom, in eleven cases less salt, and in three cases
the same, though, as before mentioned, where the
difference is only 0*02 7oo 11^ 1® l^o small to allow any
deduction to be made. The salinities are on the whole
high, but agree with Bassett’s figures for the Gulf Stream
water at his Stats. 5, 6 and 7 (spring ’08, and for the May
observations ’09). One might infer from this that Port
Erin w^as one of the places nearing the northern limit of
this current to the West of the Isle of Man, since twm
samples of water which came from a place North of Peel
in the northern tide Avere very different from any taken
off Port Erin. The salinity was only 83*737co- I flo not
think that the small differences, either in vertical
distribution or from day to day throughout the month,
would cause any great changes in the distribution of the
plankton, but a sudden lowering of the surface salinity
by heavy rain, which would affect the plankton of the
upper layers only, might cause a descent. The influence
of light and the alternation of day and night will
probably produce far greater changes, f With regard to
temperatures, a prolonged period of cold weather will

* Lancash. Sea- Fisheries Labor. Report for 1908, p. 44.

t In a series of tow-nettings taken at intervals of three hours
during 24 hours at Port Erin a great difference is noticed between the
surface catches taken at night and those during the day.

270 TRANSACTIONS LIVERPOOL FIIOLOGICAL SOCIETY.

probably kcpp bark (’ortain forms, anrl the stoady rist-'
tliroiighoiit iVpril may infliience ffipsc organisms.

Oxygen D kt f.r mi n ation s .

In tliese first oxygen observations for the Irish Sea, the
method employed was that of von AVinkler, wliicli was
used by Natterer in his work on tlie “ Pola ” exjiedition.

A number of bottles with well fitting glass stoppers,
and holding about 275 c.c., had the volume accurately
determined by weighing bottle and stopper, at first dry
and tlien filled with distilled water, the stopper being
I)laced in so that no air bubbles were by any chance
included. The glass stoppers must have no hollows under-
neath where air bubbles might possibly collect. The water
was collected as for salinity samples by the Ekman
Reversing AA^ater-bottle, but a piece of indiarubber tubing
was fixed to the tap on the bottle and the end let down to
the bottom of the glass bottle, so that the water ran in
when the tap was opened without splashing or enclosing-
air bubbles. The procedure on the yacht was as follows :
A bottle was completely filled with the sea-water to be
examined. By means of pipettes with long narrow stems,
first 2 c.c. of concentrated solution of I^aHO (56 gr. pure
caustic soda in 100 c.c. of distilled TI.O, to which 10 gr.
of potassium iodide are added) and then 1 c.c. of
manganous chloride solution (40 gr. MnC^TH^^O in
100 c.c. dist. water) were introduced carefully, so that
they remained at the bottom of the bottle. The stopper
was then inserted, causing some sea-water to overflow,
and the bottle well shaken and brought back to shore for
further treatment in the laboratory. The precipitate was
allowed to settle and then 2 c.c. or more fuming hydro-
chloric acid were added, which dissolved it, the reaction
setting free a quantity of iodine, equivalent to the oxygen

SEA-FISHERIES LABORATORY.

271

combined in the precipitate, wbicb was the quantity
formerly in the sea-water of the sample. This solution of
iodine was now titrated against standard sodium thio-
sulphate solution, using starch solution as indicator. It
is very important to test all the reagents first; addition
of the hydrochloric acid to the caustic soda solution
containing potassium iodide must cause no liberation of
iodine.

The number of samples analysed was thirty-one. The
accuracy of the analysis, however, was not like that for
chlorine. For the surface water the results were 6‘5, 6'82,
6-68, 6-8, 6-8, 6*8, 6-6, 6*6, 6-76, 676, 6’4, 6*57, 6’8 c.c.
per litre of water, and for water from twenty fathoms
630, 6-30, 6-60, 6‘.30, 6*30, 6‘60, 673, 6'3, 6'3, 6-36 c.c.%,
in all cases less than the figures for the surface water at
the same station. No particular changes were noticed
during the month. These figures correspond with those
of Niels Bjerrum for Baltic waters in ’03-’04, which also
show a general decrease of oxygen with increase in depth.

Temperature and Salinities during May and June.

These observations are given separately from the April
results since they were made at a different station (which,
however, corresponds fairly well with Professor
Herdman’s Stat. Ill of the ‘‘Ladybird” observations),
2-3 miks out from Port Erin breakwater well outside the
“ Bowlane Tide ” running down the Manx coast North of
Port Erin. Like the April observations, they were made
in conjunction with plankton catches (quantitative), and
twice a week, on Mondays and Thursdays, if weather
permitted. A sailing boat was used, the water for
salinities was taken by means of the Monaco Water-
bottle, and the surface temperatures with the usual
Bichter thermometer.

8

272 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

The particulars of the plankton
elsewhere in this report.

catches are given

Temperatures.

May 3...

8*075°C.

„ 10...

8*95

„ 13...

8*70

,, 17...

8*87

„ 21...

9*20

„ 24...

10*05

May 28... 9-57°C.

June 1... 10*45

„ 4... 10*84

„ 7... 10*09

„ 12... 10*05

June 19... 10*15°C.

„ 22... 11*05

„ 25... 11*15

„ 28... 11*12
July 1... 12*7

On the whole, the same rise of temperature with
irregular variations, as seen in April, is continued.

Salinities.

The samples were all surface water with one or two
exceptions, since there appeared to be practically no
difference between surface and deep water at this depth
(20 faths.).

Date.

Cl

°l

/oo

s

loo

Surface.

Deep.

j Surface.

Deep.

May

13

18*886

18*886

34*11

34*11

21

18*886

18*916

34*11

34*16

24

18*886

—

34*11

—

28

18*930

—

34*20

—

June

1

18*900

—

34*14

—

4

18*905

—

34*145

. —

7

18*920

—

34*18

—

12

18*89

—

34*13

—

99

14

18.90

—

34*14

—

99

19

18*90

—

34*14

—

22

18*87

—

34*09

—

99

28

18*88

18*94

34*11

34*22

July

1

18*93

—

34*20

—

The salinities show very little fluctuation throughout
the two months. The small variations can scarcely be
correlated with weather conditions at Port Erin, except

SEA-FISHERIES LABORATORY.

273

that the lowest observation, that of June 22nd, occurred
after rain. Since, however, the water from which the
samples were taken had moved from some other district,
it is quite obvious that variations might he determined by
weather conditions elsewhere. There does not appear to
have been any particular change in either temperature or
salinity conditions accompanying the sudden disappear-
ance of the Diatoms between May 21st and 28th. The
differences between surface and bottom salinity on the
three occasions when samples were taken are 0*00, 0'05
and OTl respectively.

PLANKTONIC EESULTS.

Under this heading we shall consider the plankton of
Port Erin Bay and that of the open sea outside, the
distribution of the more important groups, such as
Diatoms and Copepoda, and of selected genera of these
and other groups, the proportions of Oceanic and Neritic
species in our fauna, the relation of the plankton to
sunlight and its distribution in depth, the plankton as the
food-supply of the sea, and finally shall discuss the
results obtained by different types of net.

Plankton of Port Erin Bay.

Our aim has been to obtain tow-net gatherings taken
across Port Erin Bay on at least two days in each week
throughout the year — both fine (No. 20 silk) and coarse
(No. 9) nets being used on each occasion, thus giving four
gatherings in each week. Mr. Chadwick (by whom most
of these “ Bay ” gatherings were taken) has carried out
our intentions so well that we have in all 231 samples,
and these represent every week in the year except the
second week in January, a time of continuously bad

274 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

weather. The lowest records for any month are
14 samples in May, in July and in October, and the
highest are 32 in February and 33 in March. The average
per month is thus nearly 20 hauls.

The coarse and the fine net obtained very different
samples, both quantitatively and qualitatively. For
example, as a rule the coarse net caught more adult
Copepods, and the fine net more of the Nauplii. Conse-
quently, by adding the two hauls together we get what
may be regarded as a representative sample of the
plankton obtainable in one traverse of the bay. In
January there were 11 hauls of the coarse net ranging
from 1 to 4 c.c. in quantity, and 11 hauls of the fine net
ranging from OT to 1*4 c.c. ; and if each pair of hauls be
treated as one, the range for the month is 1*2 to 5-4 c.c.,
and the average double-catch is 2*2 c.c. In the following
table the numbers of the Diatoms and other leading
groups of organisms have been treated in a similar
manner : —

Double

hauls.

Average

Catch.

Diatoms.

Dinoflag- Cope-
ellates. poda.

Copepod

Nauplii.

Jan.

11

2-2

12,062

486

5,608

1,766

Feb.

16

1*76

23,998

178

1,708

658

Mar.

16

2-5

77,423

273

1,168

944

Apr

8

14-08

1,961,333

8,171

1,269

4,498

May

7

24-07

1,166,537

30,95'/

7,701

18,141

June

9

22-9

2,612,156

25,343

10,644

20,867

July

7

10-05

153,616

9,393

16,624

23,969

Aug.

7

6-84

8,319

3,440

20,078

14,893

Sept.

7

12-15

574,571

814

14,442

19,786

Oct.

7

5-97

27,914

289

28,935

15,879

Nov.

8

3-73

79,244

3.099

7,190

4,778

Dec.

9

-4-0

37,626

2,133

8,258

4,153

This shows that

the maximum

catch, so far as

volume is concerned, was in May ; that the Diatoms have
an extended maximum from April to June, with its
climax at the end; that the Dinoflagellates are most

SEA-FiSHERIEvS LABORATORY.

275

abundant in May and June, and especially in May; that
the adult Copepoda go on increasing till August, and,
after a drop in September, attain their highest point in
October, while the Copepod Nauplii, as might be
expected, precede the adults with a peak in June and
July, and another in September.

If we compare this record with those of former jmars,
it will be seen that in the important period of March,
April and May the present year is closely similar to ’08,
and very different from ’07 ; in June, July and August it
is intermediate between ’07 and ’08; in September it
shows an increase over the two previous years ; and
finally, in October-December it is very similar to ’08.

The diagram (fig. 6), in addition to the columns
indicating monthly averages for the three years
separately, shows, in the outer clear areas to the left, an
average for the three years taken together in each month,
and in the black areas on the right the averages for
the two years ’08 and ’09.

The record suggests the idea that ’07 was an
abnormal year. The rises in alternate months (April,
June, August and October) seem unnatural, or at least
unusual. The two last years (’08 and ’09) agree very
closely, except in June, when ’09 showed far more
plankton than ’08. If we take a median position between
these two, and connect the tops of the ’08 columns by one
line, and of the ’09 columns by another, the resulting
curves show a spring maximum culminating in May,
sinking to its lowest in August and then rising again to
a smaller maximum in September. This, we think, so far
as our evidence goes, is probably the usual form of the
annual plankton curve for Port Erin Bay, and it may be
seen in the black columns (averages of ’08 and ’09 taken
together) of the diagram (fig. 6).

276 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Tlie spring phyto-plankton maximum in ’09 does not
show any great abundance of an unusual organism, such
as the immense swarm of T'halassiosira nordenshioldii that
invaded the Irish Sea in ’07.

Fig. 6.— Diagram of average haul of Plankton per month in the
three years, separately and combined.

There was a decided second Diatom maximum this
year between September 21st and the end of the month,
very much as in ’07. It gradually died away in September
and October, and then the usual winter species of
Biddul'phia and Coscinodiscus made their appearance in
November.

Plankton Outside the Bay.

Looking at the plankton outside the bay, as shown in
the March and April gatherings from the yacht at
Stat. Ill, with the fine surface net, and continued by
Mr. Dakin’s hauls in much the same locality, with the

SEA-FISHERIES LABORATORY.

277

same net, through May and June to July 1st, and then
by the yacht’s hauls again in August, we find the
following results : —

There is a well-marked, but possibly exceptional,
early Copepod maximum of short duration from April
1st to 5th. This reaches in a haul 3,000 nauplii, 1,600
juveniles and 955 adults, is apparently due to a swarm of
Oithona, and is actually earlier than the phyto-plankton
increase which usually starts and dominates the vernal
maximum.

The Copepoda are more abundant in the surface
nets than in the Nansen nets hauled at from 20 to 10
faths. in the earlier part of April (March 27th to
April 8th), but the reverse is the case in the later part of
the month (April 13th to 26th). This is not incompatible,
however, with a general correspondence between the
surface and the deeper hauls, the two rising or falling
more or less together.

There is a marked decrease of Copepoda (as well as
of the phyto-plankton) during the few days preceding
April 9th, a period of relatively hot and very fine weather
for the time of year. The sea-temperature falls again
between the 9th and the 13th, and at that period the
Diatom and Dinoflagellate maxima begin.

In August, when, compared with April, the total
catch is very small (Q-2c.c., say, as against 4 c.c.), and
the Diatoms are at their minimum, the Copepoda are
fairly numerous, ranging up to about a thousand adults
and five thousand nauplii in a haul.

The vertical hauls with the Nansen net show the
same Oithona increase on April 1st to 5th, and also an
even greater increase of Copepoda a few days later on
April 14th to 23rd. The latter reaches a height of 5,396,
of which 5,000 are Oithona. We are inclined, however.

278 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

to regard these two peaks as unusual, and if they be
removed the Copepod curve shows a gradual rise during
May and June.

The Diatom and Dinoflagellate maxima appear about
the same time at Stat. Ill, and are in the surface
gatherings (April 13th), before they appear (Diatoms on
April 17th, and Dinoflagellates on the 19th) in the hauls
from '20 to 10 faths. It is not possible to compare the
actual volumes in these 20-10 vertical Nansen-net hauls
with those of the horizontal, 15-minutes, tow-net. The
relative volumes and the daily and monthly variations
may, however, be compared.

The Diatom and Dinoflagellate maxima extend into
May. The Diatom maximum ends between May 24th and
May 28th. The Dinoflagellates are relatively more
abundant than the Diatoms in May and June.

Diatoms and Dinoflagellates, like the Copepoda,
decrease rapidly in numbers about April 9th, after flne
weather.

Although the Dinoflagellate rise begins only a day
or two after that of the Diatoms in the second half of
April, the numbers of the Dinoflagellates keep up better
and are relatively greater than those of the Diatoms in
June.

The end of the Diatom maximum before May 28th, as
well as the fall in the amount of plankton on April 9th
and April 23rd, is shown by the Nansen vertical hauls as
clearly as by the horizontal surface nets.

The Nansen net hauls show the Diatom maximum,
throughout the water down to 20 faths., to extend from
April 19th to May 24th. During the latter part of May
and in June the Diatoms decrease in these vertical hauls
and the Dinoflagellates increase. On June 1st there are
actually more Dinoflagellates present than Diatoms.

SEA-FISHERIES LABORATORY.

279

Before the middle of June the plankton begins to increase
in quantity again, and this is seen to be due to zoo-
plankton, which now predominates over the phyto-
plankton. In fact the Diatom maximum is followed by
the appearance of Dinoflagellates, and then of Copepoda,
Sagitta and Medusae, although the increase in one or all
of these may be due to the normal life-history of the
organisms and so, perhaps, be quite independent of the
previous Diatom maximum.

A remarkable swarm of Lamellibranch larvae (pro-
bably Pecten oj)ercularis) was encountered outside the
Bay, mainly at Stat. Ill, on April 5th. A few Lamelli-
branch larvae are always present throughout the year.
On March 3Ist they reach 1,000, and in the first days of
April the numbers increase to two or three thousand per
haul, and then on April 5th there is a sudden increase to
form the maximum of 117,000 in the fine surface net at
Stat. Ill ; but other large hauls were taken also that day,
as the following table shows : —

Surf.

Coarse.

Surf.

fine.

Surf.

Old.

Surf.

Otter.

Hensen. Nansen,

Weight.

Slat. I.
Stat. III.

10,000

30,000

111,000

117,000

19,520

24,000

58,800

86,000

5,520

1,600

1,600

2,350

59,000

110,000

The numbers remain high for the next two or three
days. On the 6th one haul gave 70,000, and on the 7th
the largest haul was 55,000. After that the numbers
rapidly fell to 1,000 in June, and with occasional rather
higher records (6,000 on October 18th), died away to end
the year as it began with a few hundreds and tens. There
was no such swarm of Molluscan larvae in either of the
previous years. In ’08 the highest number was 7,500 ;
and in ’07, 2,500.

280 TRANSACTIONS LIVERPOOL lOOJ.OGlCAL SOCIETY.

Comparison of Bay with Sea.

The question arises, to what extent do the tow-
nettings taken across Port Erin Bay give a correct
indication of the condition of the Plankton in the sea
outside ? On examining our results from Stats. I and III,
and comparing with the records from the bay, we find as
follows : —

The Total Plankton reaches a much higher level
in the sea outside about the middle of May; but in June
and in August the numbers are higher in the bay. Still,
on the whole, the two curves follow the same course.

The Diatoms show no appreciable difference when
those from outside are taken into account.

The Dinoflagellata begin their summer increase
three weeks earlier in the sea outside, and in the middle
of May stand at a much higher level, but at the end of
May and in June, and also in August, they are consider-
ably lower outside than in the bay. The numbers for
Ceratium tripos are much higher throughout April
outside, reaching 15,900 in the weekly average as against
1,800 in the bay. But, on the other hand, by the end of
May the bay numbers have reached 21,000 as against 500
only outside.

Oikopleura shows very little difference, but the vernal
maximum occurs rather earlier outside the bay.

Sagitta seems to congregate in larger numbers in the
bay. It is there that all the larger hauls were made (up
to 2,100), while outside it never reaches 75 in a haul.

Tomopteris (taking the three years into account) has
its maximum in the open sea in June and July, while
inside the bay it has a still higher maximum in October.

The Copepoda agree fairly well in dates, but the
numbers per haul run larger in the bay. The largest

SEA-FISHERIES LABORATORY.

281

hauls occur, however, in the autumn, when we have no
outside data for comparison.

The Cladocera appear first outside the bay in
T7-’08, inside in ’09; the maxima appear to correspond
fairly closely in point of time, though on the whole the
numbers run higher in the bay, and the catches remain
large for a longer time in the bay than outside.

On the whole, the bay catches are richer per haul,
but in regard to the periods of occurrence of the various
organisms there does not seem to be any notable constant
difference.

Annual Position of Chief Maxima.

We have drawn curves for the three important
groups, Diatoms, Dinoflagellates and Copepoda, for each
of the three years separately, and have also superposed
the curves for the three years on one sheet in order to
determine whether the groups appear in succession in the
same order year after year. It is evident from what we
have already stated above that the maxima of the whole
plankton, and also of the component groups, are not
necessarily in the same months each year — the Diatom
vernal maximum, for example, may be in March (’07),
April (’09), or May (’08) — but still it is possible, of course,
that the relative positions may be retained, and that an
early or late season may affect all groups equally.

Our curves show in ’07 the Diatom maximum in
March, while the Dinoflagellate line showed a consider-
able rise in April and May, and a further higher peak in
July, and the Copepoda rise keeps about a month behind
the Dinoflagellates till June, when it runs up to its early
summer maximum, followed after a depression in August
by a still greater maximum in October.

In ’08 the Diatom maximum is in May, and the

282 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Dinoflagellate curve is consistently a inonth later and
readies its climax in June, while the Copepods have two
small elevations in March and June and a much greater
peak in Septemher-October. In ’09 the Diatom record is
peculiar, since there seem to be two spring maxima, April
and June, while the Dinoflagellate maximum is in May
to June and the Copepoda, in July and August.

Consequently, in all three years the order of
succession of the vernal maxima is the same, and when the
nine curves are placed together on a sheet, although there
IS of course some overlapping, the Diatoms form an earlier
and the Copepoda a later group, while the Dinoflagellates
lie between.

The autumnal maxima are much less definite. The
Copepod rise in Septemher-October is the most marked
and most regular, the Diatom increase is much less
marked than that in spring and is less regular in its
appearance, while the Dinoflagellate increase, if there is
one, is still less marked and less constant.

Important Genera of Diatoms.

Last year we took out the five leading forms,
Biddulfhia, Chcetoceros, Coscino discus, Rhizosolenia,

T halassiosivu, for separate consideration ; this year we
add a sixth, Guinardia. The first point that one remarks
in comparing the records for the two years is the close
agreement in distribution throughout the year in some of
the cases. In both years Biddul'phia begins with 4
figures in January, works up to G figures in April, dies off
to nothing at the end of May (May 20th in ’08, May 27l;h
in ’09), reaches 4 figures again suddenly on September
14th (1,180 in ’08, 1,200 in ’09), and remains present in
thousands until the end of the year. The numbers
become greater, however, towards the end of this year

SEA-FISHERIES LABORATORY.

283

than they were in ’08, and reach to over 50,000 on
November 13th and 16th. Again, Chcetoceros reaches
7 figures for the first time on April 27th in ’08, and on
April 19th and 22nd in ’09, and next on May 20th in ’08
and on May 12th in ’09 ; after which the numbers fall
during the late summer and rise again in autumn. This
second maximum was, however, both greater and earlier
this year, reaching 875,000 on September 25th, as against

70.000 on October 16th, ’08.

Coscinodiscus runs through thousands and tens of
thousands in the first three months of both years, and
reaches 120,000 on April 13th and 14th, ’08, as against

65.000 on April 7th, ’09. The numbers then rapidly
diminish, and reach zero on June 2nd in ’08 and on
June 1st in ’09, and remain low with occasional increases
until October, when they become steadier and rise to
hundreds, bordering on 1,000, in ’08, and to a few
thousands (5,500 on December 14th) in ’09.

Rhizosolenia presents a marked contrast to the above
species in being practically absent in the first few months
of the year, and having its single maximum in June. In
’08 it suddenly shows 4,700 on April 13th, and in ’09
equally suddenly, 5,000 on April 15th; then 40,000 on
April 19th, 140,000 on May 12th, 500,000 on June 9th,

1.620.000 on June 12th, and the maximum of 2,600,000 on
June 15th; ’08 has 150,000 on May 20th, 1,137,500 on
June 4th, and the maximum of three-and-a-half millions
on June 30th.

Ihalassiosira is also absent in the early months of
the year, and begins with 2,000 on April 13th in ’08, and

4.000 on April 15th in ’09. Last year the numbers
reached 80,000 on May 20th, and ended with 7,500 on
June 4th; this year the highest point, 40,000, is on
April 19th, 10,000 on May 20th, and 1,000 on May 24th,

284 TKANSACTIONS LIVERPOOL BFOLOGICAL SOCIETY.

after which the species is unrepresented. If, as seems
possible, we had in ’07 an immigration of the northern
species TlioXcLssioszTCi novdcTisTctoldiiy the numbers seem to
be gradually diminishing.

Guinardia, unlike the last two genera, is present
throughout the year. It works up from small numbers to
1,000 in April, 20,000 in May, and to a few millions in
June— 1,500,000 on June 9th, 3,000,000 on June 12th,
4,000,000 on June 15th, and 3,500,000 on June 22nd—
after which the numbers gradually fall to thousands in
July to September, hundreds in October and November,
and tens in December. In ’08 the maximum was at the
same point, and the general course through the year was
similar ; but it did not appear in our gatherings until the
middle of April— there were usually 1,000 to 4,000 during
the rest of the month. In May it reached 50,000 on 20th,
and 100,000 on 30th. The numbers were half a million on
June 4th, and the maximum of nearly a million, twice,
towards the end of the month. Then the numbers fell
rapidly to thousands in July, hundreds in August to
October, and tens in November and December — a very
similar record to that of the present year.

According to Lohmann, at Kiel, Sceletonema, which
is one of our rarer forms, is the commonest Diatom, and
attains its maxima in May- June and September-October.

Biddulphia sinensis in Port Erin Bay, 1909.

This species of Diatom was first noticed in our bay
gatherings of November 9th, ’09, when 400 specimens
were counted in the gathering from the coarse net and
40 from that of the fine. In the following haul on
November 13th about four times the quantity was present,
1,600 in the coarse and 200 in the fine; and during the
remainder of the year to December ITth numbers varying

SEA-FISHERIES LABORATORY.

285

from 1,000 and 800 down to 100 and 50 were obtained.
Altogether it was found to be present in 16 bay gatherings
during November and December, ’09. In ’08 and ’09,
Ostenfeld published papers* showing that this Indo-
Pacific species was noticed for the first time in European
waters in ’03, in the Skagerrak. It was then found to be
present in quantity in the South-eastern part of the North
Sea round about Hamburg. From this it spread north-
wards to the coast of Jutland, and in the following year
appeared on the Belgian coast also. And so it remained
for several years. In ’07 it had penetrated to the Baltic,
to the North of Scotland, and southwards to the entrance
to the Channel. The Norwegian observations show that
B. sinensis was present also in the sea off Bergen in
the same series of years, and recent reports show that it
has continued in both these sea areas up to the present
time, in each year reaching a maximum in November and
the minimum in summer (May). The view is definitely
held by Ostenfeld that this is a case of an exotic species
which was introduced accidentally (e.g., by a ship from
the East) into European waters near the mouth of the
Elbe, probably in September, 1903; and the rate of
dispersal from that point is used as an indication of the
presence and rate of flow of currents. If Ostenfeld is
correct in his interpretation of the facts, then our record
shows that the species had extended to the centre of the
Irish SejSL in ’09, and that here, as elsewhere, it reached a
maximum in November (1,600 on November 13th, and
1,000 on November 16th, in one haul of a net for
15 minutes, inside the Bay). It is, however, possible
that we have in all these records the unusual increase of
a rare species which had previously escaped observation.
It must be remembered that during the last decade far

* Medd. Komm. Havundersog. Plankton, I, 6, 1908: and Internal.

Revue d. Hydrohiol. u. Hydrogr., August, 1909.

286 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

more plankton hauls have been taken than was ever the
case before, and that these collections have been most
carefully and critically examined by experts. For
example, in the last three years nearly 2,000 gatherings
from the sea off Port Erin have been quantitatively
reported upon, while before that time 50 in the year was
probably a fair average number, and the examination of
the material was qualitative only. So it is only what
might be expected if the minuter and rarer and more
critical species are now being found to be present where
previously unrecorded ; and we know that species which
are usually rare may, through some change in the
conditions, such as the competition with allied forms,
become temporarily or locally very abundant. We have
no proof that this is the explanation of the recent
manifestation of BidduL'pliia sinensis, and we only mention
it as being worthy of consideration before we accept as
established the view that this species is a new immigrant
from the Red Sea or more eastern waters. It must be
remembered, however, as telling against this alternative
explanation, that B. sinensis was not noticed during the
two first years of our more intensive collecting, and more
exhaustive examination of the material, and that a
re-examination now of that earlier material reveals no
trace of it. We are, therefore, inclined to consider that
when this Diatom was first noticed in our nets early in
November, ’09, it had recently entered the Irish Sea for
the first time.

CoPEPODA — Adults and Larv^.

In the examination of the catches, the adult
Copepoda, the Nauplii and the young intermediate stages
(classed together as ‘‘ juveniles ”) have been counted and
recorded separately, and if we represent these records by

SEA-FISHERIES LABORATORY.

287

curves a certain amount of similarity in the distribution
throughout the year becomes evident (see fig. 7).

In all three cases the maxima are in the summer six
months, May to October inclusive. In all three cases there
are two well-marked maxima, the apices of which (taking
monthly averages) are in July and September respectively
in the case of the Nauplii and the juveniles, and in August
and October in the case of the adults. The curve for the
juveniles is very like that of the Nauplii, but has much

less elevated peaks. The Nauplii show (on the monthly
averages) an extensive maximum from the middle of May
till the middle of July, with numbers ranging from
18,000 to 24,000 per haul. The curve for the juveniles
only reaches about 12,000, and that only for a short time
in July. Then the Nauplii curve shows the second
maximum in the middle of September, reaching close on
20,000; while the curve for the juveniles shows that at
that same time of year they scarcely reached 10,000 per
net.

The curve for the adult Copepoda differs a little in
T

288 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

form from that for the juveniles. The two maxima are
present in each, and the apices for the adults are about
one month later than those for the juveniles — which is
very much what we should expect. But the numbers for
the adults are rather greater than those of the juveniles,
such as 20,000 in July as against 12,000; and the October
elevation runs up suddenly to close on 30,000, while the
corresponding peak for juveniles in September reaches
only about 10,000. It is easy from the curves to see that
the Nauplius population, after reduction by about one-
half, becomes the juvenile population; and although it is
not quite so plain, still it looks probable that tlie juvenile
curve is related to that of the adults, the latter being
possibly reinforced in its October maximum by the
immigration of swarms from neighbouring seas or from
the North Atlantic Ocean.

If we now take the off-shore Stat. I, and examine the
Copepoda in the same three stages, as caught in the fine
surface net, we find that during the spring period
(March 27th to April 26th inclusive) 19 quarter-hour
hauls of the net in question were taken at that locality
five miles off Bradda Head. The variation in the
numbers of the different stages present from day to day is
most marked in the case of the Nauplii, is less in that of
the juveniles, and is least in that of the adults. The
Nauplii run up to about 23,000 (at the end of March), the
juveniles to 8,000 (on April 13th), and the adults to 2,000
(on April 2nd and April 21st). With a more complete
series of statistics one could, doubtless, from the pro-
portions between the totals, say w’eek by week, arrive at a
correct estimate of the death-rate at each stage, at the
different times of year. The above observations from one
net at one station are probably not numerous enough for
this purpose, but the figures given — a reduction f;*om

SEA-FISHERIES LABORATORY.

289

23,000 to 2,000 — may perhaps be some indication of the
rate of destruction.

If we look next at tlie Copepoda record for Stat.
III., outside tlie Bay and along the shore to the North,
during the period from the end of March to the beginning
of duly, we find that between March 30th and April 5th
nearly all the commoner species of Copepoda increased,
but the most marked abundance was that of Oithona
(over 8,000). During the second week in April numbers
were low, then about April 13th to 25th a more general
increase set in : first Acartia became more abundant
(1,000), then P seudocolanus (2,600), and then Oithona
(over 5,000) again. Numbers were low during the greater
part of May, till the 21st, when Oithona again rose (2,750),
and again (3,800) on June 7th and June 25th (3,530).
Finally in August this species reached its maximum of
over 20,000. Acartia is most abundant at beginning of
June (9,880), and again on June 19th (7,980) and on
August 3rd (3,900). From this it is seen that the increase
of Copepoda in spring outside the Bay is mainly due to
Oithona, in June to Acartia, and in August to Oithona
again. P seudocolanus does not rise to any great maxima,
but relatively to the other Copepoda is more generally in
evidence in April than in summer.

It would be more satisfactory if we could be certain
in every case as to which adult species the Nauplii and
juveniles became. In some of tiie more important cases
they have been determined. The Nauplii at Stat. I. on
April Gth, 7th, and March 31st, and at Stat. III. on April
2nd, loth, and 17th, are mainly P seudocolanus, witii
smaller numbers of Temora, Acartia and Oithona', these
three latter were not very plentiful, and the names are
placed in the order of their relative abundance. Most of
the 8,000 “ juvenile ” Copepoda on April 13th appear to be
early stages of Acartia,

290 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Off Kiel, Lohmann finds Oithona to be the commonest
Copepod, as we do at Port Erin. At Kiel it is five times
more abundant than Paracalanus and nine times more
than Acartia. Lohmann found that at Kiel Pseudocalanus
had only a si)ring maximum (March). In Port Erin Pav
the spring maximum is in May, and a still greater
increase is found in late autumn (October).

May is the month for the chief maxima at Kiel
according to Lohmann, but at Port Erin the monthly
averages increase from May to August, there being well-
marked peaks at the end of May and beginning of June,
the end of July and the middle of August. The end of
August and the first half of September shows a depres-
sion, and then comes the greatest elevation in the year
about the middle of October. Lohmann states that at
Kiel there are few Copepoda in July and August. At
Port Erin they are quite abundant then. In the Bay on
August 2nd, ’09, there were close on 20,000 of Pseudo-
calanus alone in one net. It looks as if our maxima were
rather later than those at Kiel, Lohmann’s May maximum
being represented here in J une, and his August depression
corresponding to the September condition here.

Selected Copepoda.

In our last report we gave the full particulars of the
distribution in the Bay, throughout the year, of six
important Copepoda. This year we have taken out the
same series, along with a few additional forms, as follows :
Calanus helgolandicus, P seudocalanus elongatus, Anomalo-
cera pattersonii, Acartia dausi, Centro'pages hamatus,
Oithona similis, Temora longicornis, Paracalanus parvus,
and Microcalanus pusillus, which for the sake of brevity

SEA-FlSIlERiES LAB0RAT0R1^

291

we sliall allude to in tlie rest of this discussion by their
generic names. We have again made out detailed lists
of the occurrences on every occasion in ’09, but we do
not think it necessary to publish these : a comparison
with last year’s results will probably suffice.

PSEUDOCALANUS is again one of the most abundant
forms. It is present throughout the year, and is repre-
sented in nearly every gathering, and in many months by
high numbers, for a Copepod. The greatest numbers
caught in single hauls reached over 3,000 on occasions in
January, February and March, 7,000 in May, 5,000 in
June, 9,200 in July, 19,250 in August, 14,000 in Septem-
ber, and 23,200 and 16,900 in October, 8,100 in November
and 4,000 in December. These numbers are rather higher
tlian those of last year and not quite so high as those of
’07. Many of the monthly averages, per net, run into
thousands, and for October the number is 8,990. In the
earlier part of April it seems to be more abundant in the
deeper nets, and later in the month is more on the surface.

Calanus (see PI. D, tig. 4) is present throughout
the year, although in some months only a few individuals
V ere caught at a time. The numbers remain low, for the
most part units and tens, during the first four months,
and then on May 27th run up suddenly to 1,500. This
was probably an exceptional swarm that entered the Bay,
as next day the same net caught 95 only. In June the
numbers were generally in the hundreds, and twice (18th
and 19th) exceeded a thousand. July was much the same,
with 1,500 on the 6th and 2,000 on the 21st ; August and
September shelved units and tens and occasional hundreds,
while October had 1,800 on the 16th and 4,200 on the
18th. The end of the year like the beginning gave low
numbers only. This agrees fairly well with previous
years, but the increase in early summer is here later than

292 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

in ’08, tlioiigli almost identical in position with ’07
(fig. 8). There has been in ’09 no evidence of a really
great swarm in J nly or August such as we have
occasionally seen in former years ; but a chance observa-
tion made in duly shows how easy it is to miss such an
occurrence. The official gatherings taken on July 15th
and 21st give no evidence of any unusual numbers, but

ordinary tow-net gatherings, taken by Mr. Gravely and
Mr. Dakin for class purposes on July 17th and 19th,
yielded enormous hauls of Calanus, only portions of which
were preserved, but which it is estimated must have
reached at least 20,000 per net.

We show here (fig. 9) what we take to be the ovum,
or rather the unhatched nauplius (measuring 0*68 mm. in
diameter) of Calanus helgolandicus. That species has

SEA-FISIIERIES LABORATORY.

293

never been taken with extruded eggs attacked to the
genital segment, and it is therefore highly probable that
the fertilised ova are set free directly into the sea. We
have observed this pelagic egg from time to time for some
years, but as the embryo was too immature we were
unable to assign it to any animal. A few w^ere taken in
the ’09 collections which clearly show the Nanplins inside.

We add here a sentence published^ more than twenty
years ago by our friend the late Mr. Isaac C. Thompson,
in regard to the ova of Calaniis found in gatherings from
the Aorth of Jlorway, which he was examining at that

Fig. 9. Pelagic egg of Calanus, x23-5.

time: — ‘b . . in some of the localities about the North
Cape . . . this species \_Calanus finmarchicus, Gunner]
forms almost the entire mass in the tow-net. Its profusion
here enables us to clear up a most interesting question. It
has been often remarked that in this, as in some other
species of Copepoda, the precise manner of ovi-position is
mysterious inasmuch as females with ovisacs have never
been noticed, though carefully looked for .... It has
often struck me as probable that C at anus finmarchicus
casts its ova directly into the sea just as fishes do, and its
profusion in these northern localities has furnished the
opportunity of establishing what seems to be a clear proof

* Trans, TAverpool Biol. 8oc., Vol. Ill, pp. 80, 81, 1889.

294 TRANSACTIONS LIVERPOOL RIOLOGICAL SOCIETY.

of the truth of this tlieoiy. For on examining many
hundreds of them together, especially in the collection
No. 4, made at Hammerfest, I find small quantities of
specially granular ova scattered about, and in two
instances as if just ejected from the animal, but entangled
by the swimming feet as the animal met its doom. It is
confirmatory of these being the ova of Calanus that they
appear only in such other gatherings as contain in great
abundance this species and it almost exclusively.”

Acartia (PL B, fig. 3) is present throughout the
year, but is usually not very abundant. In January,
February and March the numbers are mostly units and
tens, rarely reaching hundreds, the highest being 450 on
February 25th. In April there is an increase to 1,000, on
the I9th; May is lower, reaching only 800; June and
July show several hauls of over 2,000 ; August has 1,400
and 1,100; September reaches 2,350 on the 29th ; October
the same number on the 2Tth ; November shows hundreds
only, and December the same, with 1,100 on the 17th.
This agrees fairly well with last year’s record, the highest
numbers are again in September and October, but last
year’s maximum, 11,000 on October 8th, was much higher
than anything attained this year.

OiTHON.A is the most generally abundant species
throughout the year. The numbers run into thousands in
every month except April, and the maxima are 15,800 in
January; 10,000 in May; 20,000 in July, and again in
August; and 50,000 on October 18th. On the whole
these numbers are greater than those of last year, when
the maximum was reached with 40,000 on September
14th; the previous year showed 30,000 on September
20th. But the general curve of the species throughout
the year is the same, and the climax is reached in late
autumn in eacli case.

SEA-riSIIERlES laboratory.

295

Temora forms a contrast to Oithona inasmucli as it
is less generally distributed throughout the year, and in
’09, for example, was not represented in any of our nets
during six out of the fifty-two weeks. In fact, Temora is
practically absent from the middle of October until the
end of March, reaches 100 late in April and 1,000 on May
8th, 5,000 on May 27th, over 3,000 several times in June
and J uly, and 9,000 on August 2nd ; after which the
numbers fall off to hundreds and tens until October 9th,
and then fall further to tens and units with occasional
periods when the species is absent. Temora, as we have
pointed out before, is distributed irregularly in swarms.

Paracalanus is again, as it was in ’08, absent during
a considerable part of spring and summer. It is unrepre-
sented in our nets during seven entire weeks. It is
present in fair quantity early in January (2,000 in one
haul on January 4th), diminishes during February and
March, is frequently absent in March, April and May,
reaches a few hundreds occasionally in June and July, a
thousand a couple of times in August and again in
September (1,900 on September 14th), and has its
maximum about the middle of October with 4,000 on the
9th, 8,700 on the 18th, and 2,800 on the 23rd. After
that the numbers remain in the hundreds, ending with
420 and 170 on December 29th.

The totals of the above six important species of Cope-
poda for the year, in the order of their abundance, are : —

Oithona similis

465,066

Temora longicornis

. 62,659

Pseudocalanus dongatus

309,973

Paracalanus 'parvus

. 54,120

Acariia dausi

63,373

Calanus helgolandicus ..

. 21,412

The actual numbers are of no importance except as
an indication of the relative abundance. It is clear that
* Oithona and P seudocalanus far outnumber the others.

296 TllAXSACTlONS LIVERl'OOL BIOLOGICAL SOCIETY.

On plotting tlie weekly averages of these six species
and drawing curves through them the fact comes out that
taking them all together the great elevations are found in
the six months May to October and the minima are in the
six winter and spring months, November to April inclu-
sive. Although the maximum for Acartia is in June,
for lemora in August, for Pseudocalanus, Faracalanua
and Oithona in October, and for Calanus in July and
October, when all are put together it is evident that the
Copepoda are a summer and autumn group, and in that
respect contrast strongly with the Diatoms, for example.

few other less important species which have been
mentioned in the previous reports will now be dealt with.

Anomalocera is practically absent, except for an
occasional straggler, up to the end of March; 25 young
specimens on the dOth and 10 on the 31st; 45 and 15 on
April 7th in mid-channel ; 25 to 30 on the 13th, 14th,
loth, 19th, and 45 on the 24th ; otherwise the numbers
are units and tens. May shows a sudden increase to 300
on the 28th, and after 40 on the 1st and 60 on the 4th of
June Anomalocera is practically absent during the
remainder of the year. In ’08 it occurred from the middle
of April to the middle of September; in ’07 it was present
in the Bay until November.

Centropages IIAMATUS is never an abundant form.
It is practically absent until May, when it appears in
units and tens, reaching 160 at the end of the month,
/^OO several times in June, 300 in July and again on
August 2nd, after which the numbers rapidly fall to tens
and units again and so remain until the end of the year.
This is one of the forms that seem to be commoner in
the Bay than in the sea outside.

Microcalanus pusillus, Sars. It will be remem-
bered that in this Eeport, Part I, p. 165, it was

\ sea-fisheries laboratory. 297

^ sliown that Microcalanus imdllus appeared in the

^ deep water, in mid-channel, to the South-west of

\ the Isle of Man in large numbers in the late summer of

! ’07, and spread late in August and early in September

up to the surface (September 11th) and into the shallow
t waters, until by September 21st it had entered Port Erin

; Bay and seemed to be generally distributed. It remained

i in evidence until the end of the year. This was inter-

; preted in the Report as being possibly ,an instance of the

! invasion of the district by a non-indigenous species.

Microcalanus does not appear in the ’06 or earlier records.
It was only described by Sars in ’03, and its distribution
was then limited to a few deep-water localities in Norway.
It has since been found ot! the N.W. coast of Scotland,
and (doubtfully) from the West of Ireland. It does not
appear to be recorded from the English Channel. If the
species was a new immigrant in the autumn of ’07, it
apparently neither left again nor died out, as we find it
persisting throughout the winter in Port Erin Bay.
Altogether it appeared in 59 gatherings between August
24th and December 23rd, ’07. In the ’08 series of
gatherings, Microcalanus appears first on January 8th in
the Bay. In April it usually occurs only in the Hensen
and Nansen closing nets fishing in the zone from 20 up to
10 faths. In autumn likewise (August 5th to September
14th) it occurs only in the Hensen and Nansen closing
nets and in the weighted open tow^-net which worked in
from 10 to 5 faths. The species was present in 49
gatherings during ’08, extending from January 8th to
September 14th.

In ’09, Microcalanus is present 123 times in all, and
occurs in the records for every month except J uly, October
and November. Outside the Bay it is usually confined to
the Hensen, Nansen and weighted nets. It occurs, how-

298 THANSACTIONS LIVEKPOOL BIOLOGICAL SOClEfY.

ever, six times in the surface net worked witk an otter-
board, four of these being at Stat. I. and two at Stat. III.
In the other surface nets it occurs on three days at Stat. I.
and on three days at vStat. III. The greatest number is
500 in the Nansen net hauled from GO faths. to the surface
on April 8th, in mid-channel ; but fairly large numbers
were also obtained sometimes on the surface in the bay,
e.y., 200 on February 24th, 300 on April 27th, 200 on
August 23rd, and 400 on December 21st.

Consequently, having once appeared in the district
in '07, this species seems to have remained during the last
two years, and, with the exception of the great haul
obtained on its first appearance (September 12th, 1907,
2,000 in net at 10 faths. and 2,500 in net at 20 faths.), the
numbers during '09 seem to be on the whole larger than
they were in '07 and 08.

The alternative to this being a case of an invasion
by a more northern species is that it is merely one of the
smaller and rarer forms which had hitherto escaped
notice. It is only 0'7 mm. in length, and was only made
known to science in '03; and since then it has been
found, by careful and critical investigation, in several
distant localities. Previous to our recent “ intensive
study," it may have passed through the meshes of the
coarser nets generally used, or may have remained
uncaptured through its rarity, or if captured may not
have been distinguished from other small forms. There
are various others of the smaller and rarer forms that we
now get more frequently, first because of the more perfect
collecting, and secondly because of the more exhaustive
examination of the material collected.

We put this forward, then, as a possible alternative
explanation, not merely in this case, but in that also of
other rarer species which seem to make their appearance

SEA-FISHERIES LABORATORY.

299

suddenly in an area where previously unknown. It is
possible that the “ sudden appearance ” which leads to
the identification is due to a local increase in numbers
permitted by some change in the environment.

Outside the hay, Microcolanus behaves pretty well
in agreement with Sars’ description of it as a mid-water
form. It appears in the open-sea nets 68 times in the
three years. In 40 of these, or almost 60 per cent., it
was present only in the vertical nets ; in only 15, or
22 per cent., does it appear in the surface nets ; and in
about 25 per cent, in the “ w^eight ” net. Thus it is
evident that Microcolanus, is at least not a surface form.
Paulsen finds it in quantity in deep hauls to the North of
Iceland.

ClRRIPEDIA.

The Balanus larvse are rather interesting. The Nauplii
(fig. 10, p. 319) begin on February 6th, reach 3,000 on
the 24th, 12,000 on March 31st and 10,000 on April 13th ;
decline to 1,100 on April 22nd, to 150 on May 12th, and
disappear at the end of May. Those of the Cypris stage
(fig. 11) appear first on April 13th, reach 900 on
May 12th, and disappear at the end of June. The
Nauplii are at their climax in early April, the Cypris in
the middle of May.

In times of first appearance (e.g., Nauplii on
February 22nd in ’07, February 13th in ’08, February 6th
in ’09) and of maxima these figures agree substantially
with those of the two previous years.

Cladocera.

The constancy of this group is remarkable — Evadne
ranging from March or April to the end of August or
September in each of the three years, and Podon from the

300 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

latter part of March or May to October. The present year
seems to have been earlier than its two predecessors in
respe(d of this ^roiip, as the following- table shows : —

Evadne nordmanni ...
Podon intermedium ...

1907.

...March 29 to September 20
...March 26 to October 9

Evadne nordmanni ...
Podon intermedium ...

1908.

...April 11 to August 27
...May 26 to October 24

Evadne nordmanni ...
Podon intermedium . . .

1909.

...March 6 to September 21
...March 15 to October 2

As to the details of the preseiit year, Kvadne appears
first in the Bay on March Gth, and the numbers remain
small in March and April, but rise rapidly into the
thousands in Msij, reaching 12,000, in the Bay, on
May 24th, and 13,000 on the 27th, and 12,000 in the coarse
surface net outside the Bay on May 24th — another case
like those quoted in our previous reports of the marked
equality in hauls indicating an even distribution. Evadne
remains fairly abundant in June and Juh^ After the
first week in August it only occurs on three occasions, the
last haul being 25 in the Bay on September 21st. The
maximum in ’08 was 12,500, on June 10th. In ’07 the
numbers were much lower throughout.

Podon occurs first in the Bay on March 15th, and the
numbers remain small until May. The maximum in the
Bay is G50, on May 8th. In the sea outside it reaches
1,000, on May 24th. It is much more constant in the
later months than Evadne, being present mostly in
hundreds and tens, and witli but few breaksj until
October 2nd, when 80 were taken by the coarse net in tlie

SEA-FISHERIES LABORATORY.

301

Tomopteris.

The species of Tomoj)tefis which occurs in our
district is the species which Daniele Eosa^ names
Tomopteris (J olinstonella) catharina (Gosse), and which
has commonly been called T. onisciformis by Carpenter
and others in this country, and T. helgolandica by Greetf,
Apstein and others on the Continent.

Tomopteris is rather irregularly distributed over the
months, is rarely very abundant, and has rather a
ditferent record in the three years. In all, we have
captured 1,083 specimens in 255 hauls of the nets, and in
1,080 hauls no specimens were obtained. The distribu-
tion is sporadic, and no localities or zones seem to be
more frequented than others. Bay and sea outside, deep
and surface nets, seem to be about equally represented in
the record. In most of the hauls a few specimens only
were obtained; many show one Tomopteris only, and in
a large number of hauls in each of the years none were
captured.

In ’07 no specimens were obtained in January,
February, March, May, June and July; in ’08 none in
January, March, May and July; in ’09, which has the
most complete record. May is the only month not
represented. There are, then, no May specimens in any
of the three years. In most of the remaining months
throughout the three years the average numbers obtained
in a haul are low units, such as 1, 2, 3 and 4; but in
March ’09, the number was I2'5, in August ’08 it was 9,
in September ’07, 11*7, and in September ’08, 14. The
greatest numbers obtained in single hauls were : —
March 31, ’09 = G8; April 15, ’09 = 28; April 17, ’09 =
34; August 4, ’08 = 23 and 20; August 7, ’08 = 200;

♦ Ttaccolte PlancAqnkh’, rf-r,, V. Anellidi, p. 247, Firenze, 1008, ■

302 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

August 15, ’07 = 25 ; August 19, ’08 = 50 ; August 20,
’08 = 35 ; August 26, ’08 = 34 ; September 12, ’08 =
38 and 37; September 15, ’08 = 120; September 19, ’07
= 85 ; September 20, ’07 = 95 and 65 ; October 7, ’08
= 65. Most, but not all, of these large hauls were taken
with the shear net or the large Nansen. If we take the
shear net as equivalent to 15, and the large Nansen
(100 cm. diam.) as equivalent to 10 of the small ordinary
nets, and make out monthly averages per unit net, it is
clear that the maximum occurs in October in the three
years taken together, and the same result is obtained
if we eliminate all the catches with larger nets and with
deep nets in the open sea, and take into consideration only
the hauls with the small open tow-net across Port Erin
Bay. There were 515 of these, representing every month
m each of the three years, and when combined they give
the following averages per net : —

Jan.

.. 0-6

April . .

,. 0-1

July .

.. 0-5

Oct.

Feb. .

.. 0-1

May

. 0

Aug. .

.. 0-7

Nov.

Mar

.. 0

June ..

. 0-1

Sept. .

.. 0-8

Dec.

Although in ’09 TomojHeris is more full}^ repre-
sented throughout the year, still nearly twice as many
specimens per haul were obtained in ’07, and nearly thrice
as many in ’08. The figures for the three years separately
are as follows : —

Total hauls Average No.

Total hauls. m which Total No. of Average No. in hauls
Tomopteris Tomopteris. in all hauls. where
occurs. represented.

1907 610 63 399 0 65 6-3

1908 571 103 945 1-65 9-17

1909 754 89 339 0-45 3-8

3 years 1,935 255 1,683 0-87 6-6

SEA-FISHERIES LABORATORY.

303

Sag ITT A.

Sagitta is represented in all months. The numbers
keep low (under 50) from J anuary to April inclusive, and
then advance to over 200 late in May, over 500 on
June 4th, 1,975 and 1,344 on June 9th, 1,012 on June 18th,
over 400 late in July and early in August, after which the
numbers run rapidly down to under 30, and then remain
for the most part at units during September and October.
In ISTovember the highest number is 115, and in December
104. The smoothed curve representing monthly averages
shows, then, one great peak in June and slighter eleva-
tions late in July and early in August, and again in
November and December. The minima are in the first
four months of the year and in September and October.
The addition of the catches made in the sea outside the
bay during April and in summer does not materially
affect the general shape of the curve.

When we compare these results with those of the two
previous years, we find that although each year has some
peculiarities, there is a general similarity. In ’07 there
was a maximum in July- August and a second lower peak
in October-November. In ’08, when the numbers as a
whole were lower, there was a maximum in the open sea
on August 7th, and again early in November. Combining
the three years, we find two distinct maxima in the year,
the first, greater one, in June- August, and the second,
much smaller, in October-November. Looking at the
largest hauls in each year, in the ordinary tow-nets we
find : —

In ’07 : On August 12th, 1,000 ; on August 15th, 1,800 ;
and on November 4th, 324.

In ’08: On June 30th, 750; on August 7th, 250; on
September 14th, 220; and on November 0th, 108.

u

304 TRANSACTIONS LIVERrOOL

BIOI.OGICAL SOCIETY.

In '09: On -hino 9tlj, 1,97.9; „n August, 2iir], 198; on
November l,st, 1.15; und on December ITtli, 164.

In the larger nets, on occasions, some even greater
numbers were obtained, such as 2,-SOO in tlie shear-net, on
March olst, 09, 2,050 in the large Nansen net on
August 4th, ’09, and 3,408 in the Yngel net on
August 8th, 08. If we omit these larger nets, the
monthly averages for the three years in the open sea are
in all cases smaller than the corresponding figures for bay
hauls.

The following table gives the totals for the three
years, and shows a remarkable constancy in the total
number of Sagitta captured, and in the numbers per haul.
When 44 is the average number caught, it is remarkable
that the poorest year does not fall below 42, and the
richest does not rise above 48 : —

Year.

Total

equivalent

hauls.

Total hauls
in which
Sagitta is
represented.

Total No.
of Sagitta.

Average No.
Average No. in hauls
in all hauls. where

represented.

1907

610

370

17,658

29

48

1908

571

353

14,675

26

42

1909

754

453

19,280

26

1907-8-9

1,935

1,176

51.613

27

44

In ’07 the average number per haul at the maxima is
126 in July and 127 in November, and in ’09 the greatest
average is 209 per haul in June. The numbers are not so
great in ’08. The minima in ’07 and ’08 are 2 per haul,
in February. Sagitta seems to breed twice in the yenr
(spring and autumn), although some reproducing
individuals may apparently be found in any month. The
summer maximum is probably the result of the spring
brood, and it is noteworthy that this climax in the Sagitta
population curve occurs distinctly later than the great

SEA-FlSIiERlES LABORATORY

305

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806 TRANSACTIONS LIVERROOL BIOJ.OGICAL SOCIETY.

vernal maxima, and at a. lime of year when several of the
most important groups of organisms in the sea are on the
wane.

We can obtain some information in regard to the
distribution of Sagitta throughout the year in otlier parts
of the British seas from the records of E. T. Browne* in
the Clyde, Gamblef at Valencia, and GoughJ at
Plymouth. If we arrange the essential facts in columns
opposite the months we get the table shown on page 305.

The Plymouth record seems to show that large
quantities are seldom obtained except in October, and that
the minimum is in March. At Valencia there are shoals
in October-November, and a scarcity in spring. In the
Clyde there is an increase in October-November, and
again a scarcity in spring, in August and in December,
and the organism is fairly common in July.

Peturning now to the Port Erin column, we find it
agrees with all the others in showing a scarcity in early
spring; has a marked maximum in June-July which has
not been noticed elsewhere ; and has a second but smaller
increase in October-Vovember which seems indicated at
the other localities also.

In the Baltic, according to Lohmann, Sagitta is
most abundant in September and onwards through the
winter— under possibly rather different conditions of
temperature and salinity from those of the Irish Sea.

OlKO PLEURA.

The common Oiko pleura dtoica is present in our
collections throughout the year, and is well represented in
every month. There is a marked winter minimum in

* Proc. Roy. Soc. Edin., Vol. XXV, p. 779, 1995.

1 Royal frisk Acad. Proc., Series III, Vol. V, p. 745, 1900.

190" ' lnvestigatiov.% Blue-books Cd. 2070, 1905, and Cd. .^837,

SEA-FISHEKIES LABORATOET.

307

December, January, February and March, when there
were never more. than a few hundred in a liaul. It is well
represented from April to November inclusive, and gets
above 3,000 in a haul in April, May, June, July, August
and September. The greatest hauls were : — April 13th,
4,600; April 19th, 5,600; May 27th, 3,600; June 22nd,
3,600; July 3rd, 3,350; July 31st, 3,000; August 2nd,
3,000; xlugust 23rd, 3,350; September 11th, 5,300;
September 18th, 7,600 ; September 25th, 3,500.

The smoothed curve representing monthly averages
shows a rounded elevation extending from April to July,
and reaching its highest point, a little over 3,000, in
June; a slight fall in August and a higher and much
sharper peak in September, reaching a maximum of
nearly 5,000. Comparing this with the two previous
years, we find that there is very close agreement with ’07,
even to such details as the amount of the greatest catch
obtained in April, 5,500 per net in ’07 and 5,600 in ’09.
There is, however, the great rise to 7,600 in September
this year, which agrees with the September maximum of
7,000 in ’08. So that, finally, this year combines the
maxima of ’07 and ’08. The winter minimum remains
constant for the three years.

Oceanic and Neritic Species.

In the tables below the attempt is made to determine
whether the plankton in Port Erin Bay during the last
three years has been more Neritic or more Oceanic in
character. We regard as Oceanic species those that
typically inhabit the open ocean, although they may also
be found in coastal waters, and which have no fixed or
resting bottom stages in their life-history, and are, in
short, boloplanktonic (Haecke]) Neritic species are those
typically found in coastal and comparatively shallow

308 TEANSACTIONS LIVERPOOL J3IOLOCaCAL SOCIETY.

waters. Most of them have fixed or resting bottom stages
in their life-history, and so fall into Haeckel’s mero-
plankton, but some Neritic forms are holoplanktonic,
being permanently free.

Table I gives a list of the species found during ’09,
with the number of days in each month on which they
occur. It also shows the number of species present each
month, and the proportion of Oceanic species. It will be
seen that only in two months (January and December) do
the Oceanic forms outnumber the Neritic, while in July
the two are equal. For the other months the percentage
of Oceanic species ranges from 40 to 48'5. This would
tend to show^ that Port Erin Bay is rather more Neritic
than Oceanic in character; that is, that in most months
more Neritic than Oceanic species occur. But that,
although true, is not the whole truth, since it recognises
in each month only the number of species that have
occurred, and not the total number of their occurrences,
nor the average number of times that Oceanic or Neritic
species occurred in each month.

Consequently, it is interesting to consider Table II
(p. 312), which gives the mean occurrence or average
number of days per month on which Oceanic and Neritic
forms, respectively, occurred, obtained by dividing the
sum of the number of days on which the various forms
(Oceanic or Neritic) occurred (= total occurrences) by the
number of species. The factor thus obtained shows the
relative constancy of the two groups of species, and the
table shows that the average for the Oceanic forms is
much higher than for the Neritic, that is, that the
Oceanic forms are a much more constant feature of the
plankton. Further, we show the percentage that each
average number of occurrence-days is of the total possible
number of plankton-days in that month, and we are

SEA-FISHERIES LABORATORY

309

^jotj I I |^jCSC<J|Tt<OOl-Oi(Mj j050i<?5i?SCC|-H(M
M 1 1

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<

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June.

Oi

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t-'

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|0: jco^r-H j 1^ 1

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Total days worked

Aclinanthes taeniata

Asterionella bleakeleyl

„ japonica

Bacillaria paradoxa

Bacteriastrum sp.

Biddiilphia mobiliensis

„ sinensis

CliKtoceros boreale

contortum

,, criophilnm

„ debile

„ decipiens

' „ densum

„ diadem a

sociale

„ teres

Coscinodiscus concinnus

,, grani

„ radiatus

Ditylium briglitwellii

Eucampia zodiacus

Guinardia flaccida

Lauderia borealis

310 TRANSACTIONS LIVERPOOL BIOLOGICAL S0CIP:TY

Dec.

1 Oi

1 1 1 1 1 I jocoor>co| I 1 jOi.ioojjoo

Nov.

1

1 ^

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1

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1

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1 jt-|t-co| 1 1 jcot-t-cocoj jtor-iot-jt--

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1 1 1 1 1 I'^i 1

Table I. — 1909 — Continued.

Total days worked

Melosira borreri

Nitzschia seriata

Rhizosolenia semispina

„ setigera

„ shrubsolei

,, stolterfothi

Streptotheca thamensis

Thalassiosira gravida

„ nordenskioldii

Tintinnopsis sp

Ceratium furca

,, fusus

,, tripos

Peridinium sp

Trochiscia sp

Noctiluca miliaris

Pleurobracbia pileus

Autolytus prolifer

Sagitta bipunctata

Tomopteris catharina

Acartia clausi

Anomalocera pattersoni

Calanus helgolandicus

SEA-FISHERIES LABORATORY

311

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312 TKAiNSACTIONS LIVERPOOL BIOLOGICAL SOCIETY

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SEA-FISIIERIES LABORATORY.

313

inclined to regard tliese percentages as the most valuable
indications of the relative occurrences. For example, in
July, Oceanic species occur on the average six days and
Neritic a little over four days; but the six represents
nearly 86 per cent, of the possible occurrences in that
month, and the four is 58 per cent. It must not be
supposed that June, with 16 species showing 115 occur-
rences, is necessarily more constant than July with 16
species making 96 occurrences, since samples were taken
on nine occasions in June but only on seven in July. Ihe
numbers for mean occurrence, seven and six, are there-
fore in this case not instructive, and the percentages 79
and 85 are, we consider, more correct. But as we give in
the tables all the figures bearing on the problem, any
possible false impression can be easily rectified.

If we enquire further into the apparently marked
Oceanic character of December, with 56 per cent, of
Oceanic species in the table, we find that Metridia lucens
is present (only in December, November and January),
while the common Neritic forms Temora, Eucam'pia,
Asterionella, Chcetoceros sociale, Rhizosolenia, NoctiLuca,
Fleurohrachia and Autolytus are all absent, and also the
less prevalent Podon and Evadne. The same explanation
can be given in the case of January, the month with the
next highest percentage of Oceanic species, and this
supports Grough’s remark that Oceanic character is
largely due to absence of Neritic forms, not to any
unusual abundance of Oceanic species. One of the most
notable points brought out by this enquiry is the fairly
even numbers of Oceanic anc^ Neritic species occurring
in each month, since the percentages in Table I range
only from 40 to about 56.

Treating the records for ’08 in the same way, we
find that the totals of Table I (the details of which need
not be printed in full) are, as shown on p. 314: —

814 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY

Dec.

28

16

57-1

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54-3

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33

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1

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1 ^

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2

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50-0

Table I. — 1907.

Total days worked

Total 0 + X

Total 0

Percentage 0

SEA-FISTTERTES LABOEATOEY

315

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316 TRANSACTIONS LIVERPOOL RTOLOOrCAL S0('1ETY.

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SEA-FISIIERIES LABORATORY.

317

The toial niimher of working days is lower, and the
total number of species obtained is, in most months,
lower. The percentages of Oceanic species (38 to 60*7)
show a wider range than in ’09, and more of the months
show an Oceanic character (5 in ’08, 2 in ’09).

The second table for that year for comparison with
that of ’09 is on p. 315, and shows that: —

The preponderance of Neritic species in April is
chiefly due to Diatoms. For example, Biddul'phia aurita
and Thalassiosira gravida occur only in this month.
Asterionella hleaheleyi, Coscinosira, 'polychorda, Nitzschia
seriata and Rhizosolenia setigera occur only in one other
month; Thalassiosira nordensldoldii and Achnanthes
tceniata in two others ; and IHtylium hrightwellii and
ChcBtoceros sociale in three others.

Our third available year, ’07, treated in the same
way, on p. 314, shows the following record: —

The percentages of Oceanic species range from 40
to 57 (being thus* intermediate between ’08 and ’09), and
four of the months show an Oceanic character.

The most noteworthy points in this record are : —
(1) the unusual variation in the number of Oceanic
species — 10 to 21 ; and (2) the very low percentage of
possible occurrences in both Oceanic and Neritic species
in September, and of Neritic in August — as shown in
Table II for that same year, on p. 316.

The more Oceanic or more Neritic character of the
month in the three years (as determined by the percentage
of Oceanic species at the foot of Table I in each case) is
seen at a glance in the following table (50 per cent, is
represented by a dash) : —

Jan.

Feb.

Mar.

Apr.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

07...

N

N

N

N

N

Oj

0

N

0

0

08...

0

0

0

N

N

—

0

N

N

N

N

0

09...

0

N

N

N

N

N

—

N

N

N

N

0

—

0

2

2

3

3

2

0

2

2

3

2

0

818 TKANSACTIONS LIVF>lU*OOL IJiOI.OG ICA 1. SOCJETV.

If the numbers of Neritic oecurrences be added up
lor each month, they show tbat mid-winter (December and
January) and mid -summer (July) are more Oceanic in
cliaracter tlian tlie intervening months, April, May and
October being the most Neritic.

“ Monotonic Plankton.

Although many naturalists in the past have recorded
the occurrence of dense crowds, “ banks ” or “ swarms ”
of some one surface animal, or the members of one group,
not merely round coasts but even in the open sea, Haeckel
was the first, in 1890, to draw attention prominently to
this important point in the distribution of the plankton,
and to give it a distinctive name. In “ Plankton-Studien,”
p. 57, he says: — “Die Zusammensetzung des Plankton
aus verscliiedenen Organismen ist sowohl in qualitativer
als in quantitativer Beziehung sehr ungleichmassig, und
ebenso ist die Yertlieilung desselben im Ocean nacli Ort
und Zeit sebr ungleicli ; diese beiden Grundsatze gelten
ebenso fiir das oceanisclie wie fiir das neritisclie
Plankton. And further on, at p, 60, be distinguishes
between “ polymiktes ’’ and “ monotones ” plankton, and
says of the latter that this monotonic plankton shows a
very homogeneous composition ; ^ and when a single pre-
vail ing species, genus or family forms more than three-
fourths of the whole mass of the plankton, he regards it
as a case of “ uniform monotonic plankton.”

Monotonic planktons are found frequently around the
British Islands, and we have described some examples
from the Irish Sea in the past. We desire to place on
record a few additional cases, and to illustrate some of
them by photo-micrographs* kindly prepared for us by
our friend Mr. Edwin Thompson of Liverpool.

* These were originally made by Mr. Thompson in the Spring of 1909,
and were shown as lantern ilhistrations to Professor Herdman’s Evening
Discourse before the British Association at Winnipeg in Angnst. Thev
have since been shown at the Royal Institution lectures (London), oh
“The Cultivation of the Sea,” in January,<^1910.

SEA-FISHERIES LABORATORY.

319

The Naiiplius and Cypris stages (tigs. 10 and 11) of
Balanus halanoides, the common rock-harnacle at Port
Erin, are sometimes found in dense swarms — the former
in March and the latter about May.

Fig. 10. Nauplius stage of Balamis. Fig. 11. — Cypris stage of Bolanvs.

We have recently tried to determine the approxi-
mate number of nauplii set free in spring by the common
Balanus living between tide-marks. This can be done
by simply collecting barnacle-covered stones in March,
laying them exposed to air in the laboratory, and after the
lapse of a few hours separating the barnacles from the
stones with the point of a knife and placing them in a
vessel containing sea-water which has been kept in the
workroom for a day. Very soon after the detached
barnacles are placed in the sea-water it will be found that
the nauplii are hatching out and swimming towards the
w

820 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

lighted side of the vessel. The water should be poured off
at intervals through a fine silk sieve, which retains the
nauplii and is afterwards washed into formalin. Fresh
sea-water is added to the vessel and the process repeated
from time to time. After twenty-four hours practically
all the nauplii will have hatched. To get at the
approximate number of nauplii produced by a single
individual, take a definite number of barnacles, say ten,
and collect all the nauplii till hatching ceases, then dilute
the collection with water to a working volume and count
the number of larvse in several separate cubic centi-
metres drawn off from the well-shaken mixture with a
wide pipette. The average of these samples is multiplied
by the number of cubic centimetres representing the
working volume, \Yhich gives the total nauplii present.
The figures obtained are then divided by ten to give the
approximate number of nauplii produced by each
barnacle. This number varies with the size and age of
the adult. We found from experiments that the large
and probably full-grown adults yielded 9,000 nauplii,
whereas half-grown ones produced only 3,600. If we
take the average as 6,000, which is probably a low amount,
and let this represent the number of nauplii produced by
every barnacle along the coasts of Lancashire, Wales and
the Isle of Man, it is clear that the zoo-plankton in a
barnacle region must be subject to enormous but* very
temporary increases in the early spring by the advent of
these larval forms.

The local abundance of adults on rocky coasts, such
as Wales and the Isle of Man, must give rise to enormous
swarms which have a very great influence on the volume
of zoo-plankton in the neighbourhood. There can be no
chance of a uniform distribution taking place over such
an area as the Irish Sea, because, apart from the natural

SEA-FISHERIES LABORATORY.

321

mortality, there is the process of metamorphosis going on
whereby the nauplius changes into the “ cypris ” stage,
which settles down after a few weeks on the sea bottom as
a young barnacle. The hatching period is probably a
very short one and the nauplii are liberated from many
barnacles at the same time. Unless the plankton is
collected at the critical moment the swarming may there-
fore escape notice. A sample of plankton collected eight
years ago in Barrow Channel consisted almost wholly of
barnacle nauplii, and supplied us with enough material
for use in the fishermen’s classes until the spring of 1910.
Although we have collected plankton every spring in the
same locality and during the same period as in 1902, we
have, so far, not again met with another swarm.

In the first part of this lleport (’08, p. 186) we
recorded a definitely localised swarm of Crab Zoeas.
These are cases of mero-planktonic organisms where the
swarm is determined no doubt by the position and time
of reproduction of the Neritic adult; but holoplanktonic
and oceanic forms give equally good examples.

On Plate A, figs. 1 and 2 show “ uniform monotonic ”
gatherings of the Dinoflagellate Ceratium trifos and of
Noctiluca miliaris — the two most abundant causes of
luminosity in the Irish Sea. Ceratium more usually
occurs in quantity in the open sea round the Isle of Man,
and Noctiluca along the coasts of Lancashire and North
Wales. Both occur in greatest abundance in late summer
or autumn. In September, ’08, one of us found Noctiluca
so plentiful at Piel, in the Barrow Channel, that estima-
tions made by collecting bottles of the water and counting
the Noctiluca showed that there were about 2,000,000 per
gallon present.

The remaining two figures on Plate A show a mono-
tonic Diatom plankton (fig. 3), consisting, however, of a

322 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

number of different genera and species, and for com-
parison with it a polymiktic plankton formed largely of
Diatoms, but containing also Polychast larvse, Cirripede
nauplii, and other animals. On Plate li all the figures
show examples of uniform monotonic planktons, both
plant and animal, the two upper being characteristic
Diatom gatherings and the two lower being from hauls
through swarms of Copepoda. Such Diatom gatherings
are commonly found in April off Port Erin, and the
Copepod swarms later in the summer.

We have several times found enormous but quite
localised swarms of Calanus helgolandicus (Plate B, fig. 4)
inside Port Erin Bay in July or August, and have filled
jars with pure gatherings of this one species which have
served to supply the University students with specimens
of this typical large Copepod for several years. Large
Acartia swarms like that from which fig. 3 was photo-
graphed have occurred late in April, in August and in
September, and other common species of Copepoda have
also occurred on occasions in large swarms, both in Port
Erin Bay and in the open sea outside.

When we obtained 2,300 Sagitta in one haul of the
shear net on March 31st, ’09, that was undoubtedly an
unusual swarm. The animal was not generally distributed
through the neighbouring parts of the sea in that density,
since a similar haul of the same net on the following day
gave 245 specimens. We might quote many similar cases,
but it seems unnecessary to multiply instances further.
^Ue may take as a final example pelagic fish eggs, in
regard to which the statement has sometimes been made
that they are uniformly distributed over very wide areas.
Our experience certainly does not support such a view.
The numbers obtained per haul are most irregular. Over
large areas very few floating eggs may be obtained, even at

SEA-FISHEEIES LABOKATORY.

323

the spawning season, and then on occasions great numbers
are found in the nets.

We have a record of a haul from the Lancashire Sea
Fisheries steamer, at 18 miles N'.W. by W. of Piel Gas
Buoy, on 6. iii. 05, in which the plankton consisted of
little else than fish eggs in quite unusual quantity. The
net was taken in at intervals of ten minutes for an hour,
but only the first sample was preserved, the other five
gatherings being returned to the sea alive. The eggs,
when examined, were found to be in all stages of develop-
ment from the beginning of segmentation to the hatching
point ; and they included eggs of plaice, haddock, whiting,
dab and fiounder. Without doubt the majority of them
would have hatched out in that immediate area.

Fig. 12.— Monotonic Phytoplankton hauls, from April.

The four jars photographed in fig. 12 show hauls of
very different volumes (13 to 100 c.c.) obtained with the
same net at the same spot within 10 days in April, ’07.

324 TRANSACTIONS LIVERROOT. BIOLOGICAL SOCIETY.

Tliey are monotonic plankton hauls, such as are
characteristic of the vernal phytoplankton, maximum in
the Irish Sea, and illustrate well the wide range in
quantity obtained on neighbouring days at that season.

Fig. 13. Monotonic Zooplankton hauls, from August.

The five jars in fig. 13 show zoo-plankton hauls taken
later in the summer with coarser nets, which had allowed
the more minute organisms to escape. These, although
not complete samples, are all notable cases of animals
that were not generally distributed, but occurred in
swarms so as to constitute a monotonic plankton.

The Food Surely of Marine Animals.

Most writers who have discussed the conditions of
life in the sea have regarded marine animals as dependent
directly or indirectly upon other animals and plants as
organised food, and have considered them all as dependent

SEA-FISHERIES LABORATORY.

325

indirectly upon tlie plants, wbicli would constitute,
therefore, the ultimate source of organised foodstuff in
the sea. In the long chain of dependent plants and
animals the plankton has been looked upon as providing
the first store of food, and, in fact, the phyto-plankton
may be regarded as the primary transformer of the
inorganic raw materials into the organic foodstuffs of the
animals.

In ’07, Putter^ claimed that the principal source of
food was not to be found in the bodies of plants and
animals, but in organic compounds dissolved in the
water. The sea was to be regarded as a nutrient fluid in
which, for example, organic carbon compounds were
present in considerable quantity. This theory, if
accepted, must be of great importance in any treatment
of the metabolism of the ocean, and hence it must be
considered here. Pabent and HenzeJ have shown quite
recently that Putter’s estimate of the organic carbon
compounds dissolved in sea-water was incorrect. Putter,
however, has lately (’09) § published another work in
which these corrections are accepted, without altering the
essential points in his theory. It is unnecessary to review
the whole work in detail here; but the subject may be
considered under three heads : —

1. Do marine animals feed on solid food?

2. Is tliis food sufficient for their needs ?

3. Is there more organic matter in solution in sea-

water than is present in solid form (as plankton) ?

There is no objection whatever, in the first place, to
be brought against the view that marine animals may

* Zeitschrift /. allgem. Physiologie. Band VII, 2 and 3 Heft. 1907.

t Wise. Meeresunt. d. deut. Meere. Ahteil. Kiel. Neue Folge, Band II,
1909.

I Henze. Pflugers ArcJiiv. d. gesamte Physiologie, etc. Bd. 123, 1908.

§ Die Erndhrung der Wassertiere. Jena, 1909.

326 TRANSACTIONS LIVERPOOL UIOLOGICAL SOCIETA\

make use of nourishment in solution. The question is not,
however, on what substances marine animals can feed,
but on what they do feed under natural conditions. With
regard to this first head, which is a biological question,
most marine animals are known to take in some solid food,
and the presence of an alimentary canal with digestive
glands, the structure of appendages or other apparatus
for catching food, and the habits of the animals, can only
be satisfactorily explained on the assumption that solid
food is necessary. Putter, however, points out that it has
often been very difficult, or even impossible, to trace any
food matter in the alimentary canal or other internal
cavities of aquatic animals,- and finds it difficult to under-
stand how Crustacea living inside sponges can obtain solid
food in the filtered water which reaches them. He also
states (this will be referred to below) that the amount of
solid food necessary for many marine animals is quite
beyond their powers of catching. It must be remembered,
however, that the absence of food in the alimentary canal
is only negative evidence, and we know too little about
the bionomics of many of these forms to draw far-reaching
conclusions. It is possible, however, that the solid food
may be insufficient in quantity to meet the demands of
the animal. Putter has calculated the amount of food
required daily for several kinds of marine animals by
measuring the quantity of oxygen used in 24 hours, and
then knowing the composition of the plankton, the
number of planktonic forms necessary for food can be
calculated.

One of us* has shown that the alimentary canal of
Copepoda contains diatoms, peridinians and flagellates.
In fact, the chief food appears to be flagellates and small

* Dakin, “Notes on the Alimentary Canal and Food of the Copepoda,”
Internationale Revue der gesamten Hydrohiologie und Hudroaraohie i
No. 6, 1. pp. 772-782.

SEA-FISHERIES LABORATORY.

327

diatoms. PtitTer, however, states that the amount found
in the alimentary canal is far too small, and that a
Calanus (sp. not given) would require 9,750,000 Thalas-
siosira nana per day, if it depended on the plankton. The
alimentary canal is, however, often found full of algal
cells and debris, and we do not know how many times it
can be filled and emptied in 24 hours. Allowing for this,
however, it may still be impossible for a Copepod to obtain
sufficient food in solid form if Putter’s estimations of the
total amount required are correct. There are many other
examples cited by Putter representing the following
groups : Protozoa, Porifera, Echinodermata, Coelen-

terata, Mollusca, Crustacea, Tunicata and Fishes; and if
the figures given are correct, it is evident that food must
be absorbed from the solution in sea-water. The balance
of biological evidence is in favour of solid food being
necessary, and hence it is only a question of an additional
method of obtaining food, and not of a substitution of
liquid for solid food. The amount of organic carbon
dissolved in the sea- water was stated by Putter in ’07 to
he 65 mg. per litre. Henze and Rahen have brought this
figure down to about 3-6 mg. per litre only. Allowing,
however, for this great change, there still appears to he
more carbon present in solution (in organic compounds)
than in the plankton. It will be seen that the amount of
organic carbon was considerably over-estimated, and it
remains therefore for the figures showing daily food
requirements to he carefully checked.

The plankton still remains as the primary food
supply, for even if it is shown that the planktonic
organisms are insufficient as food, the organic carbon
compounds present in solution can be traced, as the
products of metabolism, to the phyto-plankton which is
their ultimate source.

328 TRANSACTIONS LIVP:RrOOL BIOLOGICAL SOCIETY.

Sunshine and Plankton.

As tlie view lias frequently been expressed* that the
great vernal maximum in phyto-plankton is due to the
increase in sunlight at that time of year, it may he of
interest to give the results of the daily record of the hours
of sunshine made at the Port Erin Biological Station for
the last three years. We have them recorded in tabular
form for each day, but it will probably suffice to give here
the totals for the months : —

1907.

1908.

1909.

Average

of

3 years.

Average

•of

’08 and ’09.

January

24f

35

27

29

31

February

58

284

574

48

43

March

113

834

774

914

804

April

094

128|-

1321

1104

1304

May

. 103"

179

1984

1604

188|

June

81

1544

160"

1311

1574

July

. 143

111"

1224

1254

1164

August

. 1034

118

1304

1174

1244

September

. 12U

60

122"

1014

91

October

46|-

81

61

62f

71

November

44

554

584

524

57

December

134

21

394

244

304

As ’07 may have been to some extent an abnormal
year — the sunshine in April is less than in March, and in
June is less than in any of the three following months —
we have added in the right hand column of the table the
monthly averages of the two years ’08 and ’09; and the
curves in fig. 14 show these averages and those of the
Bay plankton for the two years in question. The
similarity in these two curves is considerable — both show
the maximum in May, and a smaller but distinct elevation
in August-September, the plankton curve appearing to
follow that of the sunshine.

* E.g., by Sir John Murray, and possibly by others before him.

SEA-FISHERIES LABORATORY.

329

If, now, we take tlie very different and possibly
exceptional montbly distribution of sunshine in ’07, and
represent it as a curve (fig. 15) along with the curve of
the monthly plankton of that year, we get the curious
result of four sunshine elevations in March, May, July
and September, and four plankton elevations in April,
June, August and October. It is true that the highest
sunshine peak is in July, and the highest plankton peak
in April, but that difference in degree may be due to the

action of other factors, such as periodicity in life-histories
and succession of species throughout the year; and after
noting all difierences, the curious correspondence between
these two curves for ’07 is remarkable, and it is the more
striking when we remember that in the two years since
(’08 and ’09, fig. 14), when the distribution of sunshine
showed a marked maximum in May, the plankton

330 TRANSACTIONS LIVERPOOl^ BIOLOGICAL SOCIETY.

maximum was also in that month ; so that, in fact, as the
figures show, each of the two very different sunshine
curves is followed by a closely similar plankton curve.

With the view of testing whether there seemed to be
any correspondence between the sunshine day by day and
the plankton, especially the surface phyto-plankton,
exposures were made with Wynne’s “ Actinometer ”

on every possible occasion in the Easter vacation, ’09.
Between March 29th and April 26th the actinometer
readings varied from two seconds on April 9th (bright
sunshine and a clear sky) to 13-5 seconds on March 31st
(sky overcast, no sun visible). The actinometer reading
was generally taken on the way out to sea, half-an-hour
or so before the plankton nets were hauled. Frequently
a second reading was taken on the return journey, and

SEA-FISHERIES LABORATORY.

331

the two generally agreed closely. Although there does
not seem to he any connection between the plankton
catches and the daily variations in the actinometer, still
there does seem to be a relation between the marked rise
in all the plankton nets on April 13th and the permanent
increase in the amount of sunlight which set in a week
before. On April 5th the actinometer reading was 12’5
seconds, on April 6th it was 3‘5, and from that time till
the end of the month it ranged only between 2 and 6
seconds, and the average for the week preceding the great
increase in plankton was 3*3 seconds, while for the week
previous to that (March 30th to April 5th) the average of
the actinometer readings was 9*9 seconds. The threefold
increase in the sunlight from 9*9 to 3‘3 seconds was
followed after a week by an eight-fold increase of the
surface phyto-plankton (from about 100,000 to about
800,000 Diatoms per haul). This actinometer series of
observations tends to confirm the correspondence between
total hours of sunshine and the volume of the plankton
noted above.

During this period the sea-temperature (surface) did
not vary much, the curve being a great contrast to that
of the sunshine. In the month from March 27th to
April 26th the temperature of the water rose only 1 degree
Centigrade, from 7T° C. to 8T° C. ; and during the four
days from April 5th to 9th, when the sunshine record
increased from 12‘5 seconds to 2 seconds (by the actino-
meter), the sea-temperature increased only from 7'075° to
7*9° C., and the average of the five observations on these
days is 7*555° C. It is clear, then, that change in tempera-
ture will not account for the sudden increase in the
plankton which seems to have begun on April 9th or lOth
—after five days of increased sunshine.

The present year seems to have shown an unusual

832 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

amount of sunshine in April and May, and possibly the
increase of plankton in June over ’08 may be due to that
cause.

This is probably tlie best place to show (%. 16) the
weekly variations in the temperature of sea and air in
Port Erin Bay, as recorded at the Biological Station. For
comparison we give also the diagram (fig. IT) printed in
last Keport, showing the temperature variations in ’08.
We have not a diagram for ’07, but we have the series of
weekly records corresponding to those of ’08 and ’09. It
will be seen that this year (’09) the air-temperature whole
line, in place of crossing the dotted line representing the
sea- temperatures at one point (the first week in May in
both ’07 and ’08), nearly reaches it at the end of March,
crosses it early in April and back again at the end of the
month, gets above it again in the beginning of May, and
dips under and up again for the last time in the middle
of that month. After that there is less difference between
the temperature of sea and air during the summer than
in the previous year, and the air-temperature reaches
58° F. only, in place of 61°, but remains above the sea
longer in autumn, to August 21st in place of August 5th
in ’08.

Vertical Hauls.

The two vertical closing nets we have had in most
frequent use during the three years are called briefly the
‘^Hensen” and the “Nansen.” The “ Hensen ” was
obtained from Kiel, and is a quantitative net of the same
size as the “ Medium Apstein,” but provided with two
brass semi-circular flaps at the mouth, so that it can be
closed at any depth by the action of a “ messenger ” sent
down the line. Strictly speaking, it is the “ Petersen-
Hensen net, but that name is too long for every-day use

SEA-FISHERIES LABORATORY

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Fig. 17,

334 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

on board ship. The Nansen ’’ net is the smallest of the
three sizes made at the Central Laboratory in
Christiania, and has a mouth of 35 cm. in diameter. We
also have on the yacht the largest size, measuring 100 cm.
across, but it is the smaller size that is meant when the
word “ Nansen ” alone is used in this Eeport. This net
is also closed by the action of a brass messenger running
down the line.

Our Hensen and Nansen nets are both made of No. 20
silk, but are not strictly comparable, because of differences
in shape and size. As a rule the Nansen catches more
than the Hensen does. The two sets of catches are there-
fore treated separately in what follows: —

Hensen Net Hauls in 20 to 10 fathoms.

In the three years (T7-’09) our closing modification
of the Hensen quantitative net has been used in all 231
times, and of these 141 represent gatherings made
vertically in the zone of 20-10 faths.

Stat. I, 5 miles off Bradda Head, is the locality where
the greatest number of hauls was taken in each of the
years (18 in ’07, 28 in ’08, and 26 in ’09 , and where,
therefore, a comparison may most naturally be made.

Station I.

Easter.

No. of Hauls.

Range in c.c.

Average

Catch.

1907

12

0-5 to 9-5

3*2

1908

11

0-1 •„ 1-3

0*5

1909

19

0-15 „ 3-5

M

Station T.

Summer.

Average

No. of Hauls.

Range in c.c.

Catch.

1907

6

0*05 to 0-75

0*4

1908

17

0-1 „ 1-5

0*7

1909

7

0-3 „ 0*8

0*5

Plate A

Fig. 1. Peridinian Plankton, consisting
mainly of Ceratium tripos.

Fig. "1. Plankton, consisting almost
wholly of Noctiluca iniliaris.

Fig. 3. Diatom Plankton, consisting
mainly of Coscinodisciis and Biddulphia.

Fig. 4. IMixed Plankton, consisting of
Diatoms, Nauplii, Polychaet larvae, &c.

Plate B

Fig. 1. Diatom Plankton, consisting
mainly of Bhizosolenia semis'pina.

Fig. 8. Copepod Plankton, consisting mainly
of Acartia discaudata. One Temora is seen.

Fig. 4. Copepod Plankton, consisting
wholly of Calanus hdqolandicus.

Fig. 2 Diatom Plankton, consisting
mainly of Thalassiosirn nordenskinldu .

SEA-FISHERIES LABORATORY.

335

We have already shown that some unusually large
catches were made in the spring of ’07, and if we omit
that period then the remaining averages range from 0'4 to
I'l c.c. In fact, if three exceptional hauls at the
beginning of April, ’07, be left out of account, that year
would come into range with the others, and the normal
catch for this net, pulled through these 10 faths. of
water, in April and August together, would then appear
to be about three-quarters of a cubic centimetre. The
average for April is rather higher than that for August.

In looking at the details of the numbers of Diatoms,
Dinoflagellates and Copepoda (to take only the main
groups) for all the Ilensen net hauls (all stations) in the
three years, one notices far larger quantities of Diatoms
(amounting to millions on several occasions) and Dino-
flagellates (a few thousands) in the earlier part of April
in ’07 than 'in the corresponding period of the other two
years ; while again, in ’09, the phytoplankton was more
abundant in the latter part of April than at that time in
the previous two years ; but apart from this, there is
considerable similarity in the three series. The Copepoda
(adults, juveniles and nauplii) especially show substantial
agreement. In August the Dinoflagellates are distinctly
more abundant in the ’08 hauls than in the other two
years.

Nansen Net Hauls in 20 to 10 fathoms.

In the three years (’07-’09) the Nansen closing net,
of 35 cm. diameter at mouth, and made of No. 20 silk, has
been used in all 266 times, and of these 141 represent
gatherings made vertically in the zone of 20-10 faths., the
same number as in the case of the Hensen net.

At Stat. I, in all, 73 hauls were taken (20 in ’07,
28 in ’08, and 25 in ’09) with the results given here ; —

X

336 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Easter.

Station I.

Average

No. of Hauls. Range in c.c. Catch.

1907

13

20

to 77-0

23-2

1908

11

0-1

„ 8-0

2-0

1909

19

0-4

„ 18-7

2-9

Station I.

Summer.

No. of Hauls.

Range in c.c.

Average

Catch.

1907

7

0-5 to 4-0

1-7

1908

17

0-1 „ 1-0

0-5

1909

6

0-3 „ 1-0

0-6

Nearly all these results are larger than those obtained
with the Hensen net, and the amount credited to Easter,
’07, is surprisingly greater than all the others. That
figure depends, however, upon a few quite exceptional
hauls obtained at the time of the Diatom maximum. If
we omit that period the remaining averages range from
0’5 to 2'9. The average of this net for April is about 2*5,
and for August about 0 9. Eor April and summer together
the average is about 1*7, as against about 0‘7 for the
Hensen net.

.The remarks made as to the distribution of the
Diatoms, Dinofiagellates and Copepoda throughout the
years under the Hensen net apply here also. The Diatoms
rise to 17 millions twice, as against 2} millions in the
Hensen net, and the Dinofiagellates to 37 thousand
against 2 thousand in the Hensen. In ’09 the Dino-
flagellates reach 20 thousand in April, while in ’08 the
highest point is 3,600. The Copepoda, like most other
groups, are fewer per haul in ’08 than in ’07 and ’09.

If it is questionable whether the results of the
Hensen and Nansen nets are strictly comparable, it is

SEA-FISHERIES LABORATORY. 337

Fig. 18. — Nansen Net: at left
hand when fishing ; at right hand
being hauled up, closed. B, brass
bucket ; G, canvas front to net ;
L, releasing apparatus actuated
by M, messenger running on line ;
T, throttling noose constricting
net; W, weight.

still more doubtful wbetber
these vertical hauls can be
brought into relation with
those of the horizontal surface
tow-nets. However, we add here
(p. 338) another table of Easter
and Summer results at Stat.
I, in the three years, taken
from the records of the ‘‘ tine
surface ” net. This net has
nearly the same diameter of
opening as the vertical nets,
and is made of the same No.
20 silk. It is towed for
15 minutes while the vessel is
going dead slow,” and
probably passes through about
a quarter of a mile of sea.
Whether a column of water a
quarter of a mile in length
is strained through the net is
quite another matter, and
it is practically certain to be
less, but how much less is very
doubtful.

Looking at these figures
along with those of the
Nansen net, and omitting
Easter, '07, we find that the
two series are not very different,
and that the surface net,
as might be expected, gives,
on the whole, larger catches.
It certainly strains a larger
volume of water, and that it

888 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

does not show a proportionately still larger catch than it
does must be due to the fact that a large proportion of the
organisms in the sea are not at the surface, but some way
below. We have given elsewhere evidence that the most
populous zone is really above the part strained by these
vertical nets (20 to 10 faths.), but the water just below
and about 10 faths., sampled by the ISTansen net, is
probably on many occasions richer in organisms than the
top few feet through which the surface net is hauled.

Station I.

Easter.

Average

No. of Hauls. Range in c.c. Catch.

1907...

24 2-5 to 20-5 11-8

23 0*5 „ 6-0 2-2

19 0-5 „ 10-7 3-9

1908

1909

Station I.

Summer.

Average

No. of Hauls Range in c.c. Catch.

1907

21 1-0 to 7-5 2-7

30 0-2 „ 7-5 1-0

7 0-1 „ 2-0 0*6

1908

1909

Some T ertical Hauls in Deeper W^ater.

IVe have a series of five dates, two on adjoining days
in April and three early in August, when series of
vertical hauls were taken at a station in mid-channel with
closing nets, at specified zones of depth between 60 faths.
and the surface.

The more important results are shown in the
following table : —

SEA-FISIIERIES LABORATORY.

339

1909.

Zone.

Diatoms.

Dino-

flagellates.

Copepoda.
Adults. Nauplii.

April 7 ...

60-40

10,525

100

10

300

40-20

14,521

130

20

320

Hensen ,

20-10

14,235

380

26

560

60-0

19,260

365

141

720

April 8 ...

60-40

12,475

300

35

750

40-20

62,120

1,500

142

3,600

Hensen

20-10

20,420

640

91

2,000

60-0

86,250

1,600

115

4,900

Aug. 6 ...

60-40

180

230

254

410

40-20

100

60

195

390

Nansen

20-10

110

10

270

1,140

10-0

80

—

291

1,190

Aug. 7 ...

60-40

35

10

116

235

40-20

40

5

85

50

Nansen

20-10

50

25

32

190

10-0

180

30

1,900

480

Aug. 10 ...

60-40

440

30

230

440

40-20

545

40

282

165

Nansen

20-10

735

40

267

570

10-0

120

60

1,928

2,510

On April 7tli, in addition to a vertical lianl from
bottom (60 fatlis.) to surface, hauls with the Petersen-
Hensen closing net were taken through the zones 60-40,
40-20 and 20-10, but no vertical haul was taken in
10-0 faths. The figures show in every case some increase
in numbers in passing upwards towards the surface, and
the zone 20-10 contains the largest population. It will
be noticed that this zone is only 10 faths., half the extent
of haul in the two deeper zones.

On April 8th the hauls were the same, but the
liighest numbers are now in the middle zone, 40-20 faths ,
and next comes the upper zone. The lowest zone, as oxi
the previous day^ contains least life. In August an
additional vertical haul through the most superficial
zone, 10-0 faths., was always taken. On August 6th the
plankton is fairly well distributed through the layers.

340 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

On August 7tli there is a well-marked increase upwards,
so that most of the plankton comes to be in the zone
10-0 faths. Finally, on August 10th, with the exception
of the Diatoms, there is again an increase upwards, and
most of the organisms are, as in most other cases, in the
top 10 fatlis. This supports the conclusion we arrived at
in the first part of this Deport (’08, p. 130), that the most
populous zone in the Irish Sea is below the surface but
above 10 faths., and is in some cases between 5 and 10
fatlis.

Limitations of A^ertical Hauls.

Beyond the above general conclusions as to the
average catch, and as to the proportionate representation
of the chief groups in the different seasons and zones of
depth, we do not consider it possible to go. For the
purpose of testing the reliability of the evidence given by
the vertical closing nets in regard to further details, viz.,
the numbers and distribution of species, we have, in the
first instance, made a careful examination of certain pairs
of hauls made through the same distance, in exactly the
same way, at the same spot and within a few minutes of
each other. During the three years 14 such double hauls
have been made. In no case did the two nets contain
exactly the same species, in one case as many as ten
species present in one haul being unrepresented in the
other. This was on August 7th, ’09, in mid-channel,
about 13 miles from land, the net being the Aansen
hauled from 20 to 10 faths. The species were : —
Chcetoceros teres, C. criophilum, Coscinodiscus radiatus,
Rhizosolenia shruhsolei, Ceratium fusu's, C. tripos, Peri-
dinium sp., larval Polychteta, Acartia dausi, and Micro-
calanus pusillus.

SEA-FISHERIES LABORATORY.

341

Again, tlie species represented in botli hauls of a pair
are often present in very different numbers. For example,
on August 6tli, ’09, at the mid-channel station, when the
Nansen net was hauled twice from 60 faths. to the surface,
one haul had 6,420 Copepod nauplii, the other only 300.
On August 7th, ’09, at the same place, with the Nansen
net hauled through 60-40 faths., one haul had 15 Oithona
and 17 Microcalanus, while the other had 2 and 1 respec-
tively. On August 17th, ’08, in mid-channel, when the
Nansen net was hauled from 60 faths. to the surface, one
net had 6,250 Ceratium furca, the other only 750. It is
thus evident that, even leaving out of the question
organisms too small to be retained by the net, a given
vertical haul cannot be regarded as necessarily offering a
true picture either of the number of species present or of
their relative amounts.

Further evidence of this may be got from considering
the following series of hauls through different depths,
using the same net : —

On April 24th, ’08, at Stat. I, the Nansen net hauled
from 20 to 10 faths. contained 11 species not present in
the same net hauled from 20 faths. to the surface (e.g., 500
Ceratium trvpos), and of the 19 species common to both,
the net hauled through 20-10 faths. had the larger
numbers in 15 cases, e.g., 30,000 Clicetoceros socials to 250,
and 20,000 Chcetoceros teres to 1,200.

On September 14th, ’08, at Stat. IV, the Nansen net
was hauled from 10 to 5 faths., and from 10 faths. to the
surface. The 10-5 faths. catch had 9 species not present
in the other, and had more of all the species common to
the two except in the case of Oihopleura.

On August 7th, ’09, in mid-channel, the following
hauls were made with the Nansen net: — 10-0 faths.
(twice), 20-10 faths. (twice), 40-20 faths. (twice), 60-40

342 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

faths. (twice), 69-0 faths., and 73-0 fatlis. Coseinodiscus
concinnus occurred only in the 69-0 faths. haul;
Guinardia flaccida only in one 60-40 faths. haul;
Gauderia hoTealis only in the 73-0 faths. ; Ceratium furcd
in one 60-40 faths., and one 40-20 faths. ; Trochiscia sj).
only in one 20-10 faths. haul.

On another occasion, when hauls were made at
varying depths from 60 to 10 faths., and one from 60 faths.
to the surface, Oihojdeura was present in all the hauls up
to 10 faths., but absent from the haul from 60 faths. to
the surface.

AVe have also observed how frequently the pictures
presented by the Hensen and Nansen nets differ, Avith
regard both to the number of species present and to their
vertical distribution. Thus, on April 8th, ’09, at the mid-
channel station, the Hensen and the Nansen nets were
hauled as follows 60-40 faths., 40-20 faths., 20-10
faths., and 60-0 faths. C oscinodiscus grani was present in
the Hensen net in the 60-0 faths. haul only, and with this
evidence alone one Avould say it was present only in the
upper layers. But in the Nansen net it occurred in the
60-40 faths. haul only, thus giving grounds for supposing
that it was fairly uniformly distributed, but had escaped
the other hauls. On several occasions, Avhen the Hensen
and Nansen nets have been worked together, one of them
has had species not represented in the other.

Further, when the vertical nets are hauled to the
surface, it is often advisable to check their results by
comparing with the surface nets. Thus, on September
14th, 08, at Stat. I\, both Hensen and Nansen nets
hauled to the surface had missed the following species: —
Chaitoceros contortum, Rhizosolenia shruhsolei, R. stolter-
fotlii, Mitraria,” Podon intermedium, Anomalocera
2^eittei soni and Microcedanus ggu^illus. This was observed

SEA-FISHERIES LABORATORY.

343

on several otlier occasions, and shows that the vertical
closing nets, even when more than one hanl is made, may
miss many of the species present. These various examples
will suffice to show that vertical hauls do not give such
truly representative samples as has sometimes been
supposed, that results taken from a few hauls only may
be deceptive, and that it is advisable to check the
accuracy by taking duplicate observations whenever
possible.

Necessity for Frequent Vertical Hauls.

It has sometimes been said that if vertical hauls be
taken from the bottom to the surface, they are bound to
show everything that is present in the area, and to
represent each constituent of the plankton in its true
proportion. It has been argued that while the surface
plankton may vary greatly, and therefore the surface nets
may give partial or deceptive samples, the various groups
of the plankton, however much they may rise or fall or
segregate into zones, must always be somewhere between
the bottom and the surface, and therefore must all be
sampled by a vertical haul. That may be the case in many
localities, but it is not necessarily the case always. It
must be remembered that some groups of organisms move
not merely up and down, but also laterally, so as to reach
and occupy some narrow gulley or some deeper hole, and
in that case a vertical haul might capture that particular
group of organisms or might escape doing so, and even a
small series of vertical hauls might, through this segrega-
tion, which is horizontal as well as vertical, give quite a
deceptive impression of the constitution of the plankton.
This possibility is exemplified in the accompanying
diagram, which represents a section across a fjord or sea-
loch with an irregular bottom having a ridge at E, a

344 TRANSACTIONS LIVERPOOL lilOLOGICAL SOCIETY.

deeper gulley at D, which descends to over 50 faths., and a
shallower area at S. If we suppose that, as is actually the
case in many localities, such Copepoda as Calanus helgo-
landiciis or Euchceta norvegica are at certain times of the
year confined to the deep water below 50 faths., then they
would occupy the shaded area at D which is below about
two-fifths of the surface of the water, and in volume is
about one-fifth of the whole. If four equidistant vertical
hauls (1, 2, 3 and 4) are taken across the loch, these
Copepoda (say, Calanus) will appear in one quarter of the
samples, and if vertical hauls 1 and 2 only are taken
Calanus will appear in one half of the material, while if
hauls 2, 3 and 4 are taken no samples of Calanus will be

obtained. In every one of these cases, if the haul or hauls
were taken as representative of the whole area, the result
obtained would he erroneous. The real distribution in
this case is that Calanus occupies one-fifth of the whole
mass of the water ; but if one considered only the number
of square metres underneath which vertical hauls showed
Calanus, the conclusion arrived at would be two-fifths,
twice too much. If haul 1 only were examined, it might
be thought that Calanus was universally present, if haul 3
that it was absent, and if hauls 1 and 2 that it was present
in half the water, much too large a result— the conclusion
being that results obtained from few and distant hauls
are liable to be deceptive.

SEA-FISHERIES LABORATORY.
COMPARISOIN OF NeTS.

345

It may be worth while to attempt to arrive at some
estimate of the catching power of each net by considering
all the evidence obtained in three years as to the
performances of the different nets at the different stations.
We shall not take the time of year into account, bnt as
we have some evidence that the years differed in
character, we shall in the first instance keep these
distinct ; it is easy to combine them afterwards if wished.
We shall give, then, one figure per net at each locality in
each year. For example, we find that the Nansen net was
used in 20-10 faths., at Stat. I, 25 times in ’09, and the
average catch was 2‘3 c.c., and the average for all stations
(49 hauls) in that year was 2*4 c.c. — a fairly close
agreement.

It is doubtful whether these figures will help us
much in forming a true picture of the performances of
the nets, except possibly in the totals based on a
considerable number of hauls. Looking at the averages
for all stations in each year, as shown in the right hand
column, it is clear that, as we have pointed out before,
the exceptionally large hauls in April, ’07, have raised
the figures for that year unduly. On the other hand, the
catches in ’08 were possibly abnormally small. Those for
’09 or an intermediate series between those for ’08 and
’09, would probably be the best approximation to the
usual catching power of the net in these seas, and under
the conditions employed. Thus the figure for the Hensen
net would be about I c.c., for the Nansen nearly 2, for
the weight net and the fine surface net nearly 3, and for
the corresponding net with ? coarser mesh about 5. We
have placed the number for the larger nets in a table by
themselves, as they are clearly not comparable with the

1007.

34() TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIE

TY.

1 _

2 S ^ d

00

lO

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47

99

255

415

I’S s = S

lO

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1

1

1

pH

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l> o — P

1

1

1

ds

05

<

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d '+H r-

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O eg

1

1

1

111

o

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•verag
catch
per
haul
in c.c.

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10-9

6-03

5-2

H

03

CQ

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58

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bc.n , ^ d

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SEA-FlSHERIES LABORATORY.

34

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> o

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CD —
CO (M
(N

BP'S

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0=^0

S *=0

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348 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

4)

verag
catch
per
haul
in c.e.

JO

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(7)

1-4

2-4

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verage
catch
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Ci

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1

SEA-FISHERIES LABORATORY,

349

tr I

1

Average
catch
per
haul
in c.c.

34-07

25-8

CO

63-1

19-6

^ 1
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1

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in c.c.

30-5

36-0

1

1

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No. of
hauls.

-

-

1

>

1-H

Average
catch
per
haul
in c.c.

CO

38-0

1

1

50-0

Stat

No. of
hauls.

lO

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1

1

-

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i

Average
catch
per
haul
in c.c.

1

37-5

00

rH

Tji

CM

CD

lO

1

H

H

m

1

No. of
hauls.

00

CO

CO

1

HH

Average
catch
per
haul
in c.c.

13-2

13-0

1

o

00

1

<1

H

m

No. of
hauls.

CO

-

1

-

1

\

Average
catch
per
haul
in c.c.

31-5

35-3

23-5

13-6

I s
1 ^

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No. of
hauls.

CO

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Net.

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Shear, ’0
’0

> c

, la §>
tS 3

350 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

others. It is seen that the shear net is fairly constant
throughout the three years, with a value of about 26 to
37. The number for the Yngel trawl is about twice that ;
but the hauls of the Yngel and the large Nansen have
been as yet too few to lead to any sure conclusions.

Effect of the Propeller on Nets at Stern.

In Part II of this Peport, last year, we alluded to
the criticism that had been made by Professor Kofoid
(and possibly by others since) that the effect of the
steamer’s propeller in mixing up water of different levels
might account for the differences that we sometimes
found between the catches of twm similar surface nets
towed over the stern. After stating the conditions of the
case last year, we continued: ‘'these are all points that
ought to be cleared up by experiment, and we propose to
deal wdth them in the coming season, and to compare, for
example, the catches in nets towed some little way off
the side of the ship with similar nets towed behind.”

During the past year we have carried out this
intention; and we have now a long series of observations
made under similar conditions at two different times of
year, April and August. AYe attached one of the two
exactly similar surface nets to an otter-board which was
towed from a position forward of the foremast on the
starboard side, so as to carry it out about 20 feet from the
side of the boat amidships. The other net was in the
usual position over the stern. If there were any force in
the criticism, the “ otter-net,” which was certainly
sampling surface water quite undisturbed by the pro-
peller, or any other part of the ship, ought to give results
differing from those obtained from the net at the stern in
water w^hich might be supposed to be affected by the
action of the propeller; but no such difference is to be
seen. In 44 hauls of each net, taken in April, ’09, the

SEA-FISHERIES LABORATORY.

351

average catch for the otter net is 3‘53 c.c., and for the
stern net 4*30 c.c. Out of the 44 double hauls, the amount
of the catch in the two nets does not differ by more than
0*0 c.c. in 19 cases, in 8 of which it differs by not more
than 0*2 c.c. In 16 cases the catches differ by 1 c.c. or
over. The average difference is 0*76 c.c.

In 27 cases out of the 44 the stern net caught more
than the otter net, in 13 the reverse was the case, and in
4 pairs of hauls the catches made by the two nets were
equal. As examples of cases where two very different hauls
were made (just as was sometimes the case with two nets
at the stern), the stern net caught 8*5 c.c. and the otter
only 2*2 c.c. ; and again, the stern net caught 9*4 c.c. and
the otter 4*5 c.c. In fact, it is obvious that the otter net
gave the same kind of catch as it would have done if it
bad been placed beside its fellow at the stern.

As a further test, however, we propose this coming
season to use two otter-nets, one on each side of the ship,
for comparison both with the stern nets and with one
another. If any difference shown between the two otter-
nets is as great as the difference between the stern nets^ it
is clear that the variations are real and not due to an}^
supposed action of the propeller or other influence of the
ship.

As to the organisms present, in five cases the catches
are remarkably similar. As an example, take April 22nd,
Stat. III:--

Total Catch. Diatoms. Dinofl. Copepoda.

Otter , 7-2 c.c. 513,650 9,500 61

8tern 6-8 515,050 3,400 70

Weight 7 568,200 1,500 105

Echin. Copep.

larvae. Naupl. Oikopleura.

Otter 100 900 400

Stem 100 800 400

Weight 100 500 010

Y

85‘2 TllANSACTrONS LIVERPOOL BIOLOGICAL SOCIETY.

Here 111 contrcist is an exmiip]© of two verv dissimilar
hauls taken on April 9tli at Slat. Ill: —

Polychaet

Catcli. Dititonis, })inofl. Copepocla. larvae.

Otter 0-8 c.c. 21,425 600 4 0

Stern 1-2 43,800 250 15 100

^Veight 1-0 20,000 3,800 218 800

Echin. Copep. Oiko-. Fish

larvsp, Naupl. pleura. Eggs.

Otter 20 200 1 54

Stern 1,000 500 50 19

^Veight 2,000 7,800 800 2

\V e g’ive also an example of a case where, altliougdi
the two nets caught the same quantity, the catch was
made up of very different organisms, viz., April 2nd,
Stat. Ill: —

Total Diatoms. Dinofl. Gopepoda. Polycliset
Catch.

Otter 4 c.c. 139,000 2,750 1,316 750

^tern 4 116,750 4,000 2,511 1,000

4-7 147,750 2,550 2,790 l,7oO

Echin. Copep. Oiko- Fish

larvae. Naupl. pleura. Eggs.

^^tter 750 9,000 530 4~

^tern 500 14,000 1,000 3

eight 250 5,000 1,100 5~

In most cases the similar net, used at the same time,
w’itli a weight attached so as to keep it a few fathoms
below the surface, gave rather a larger haul. We have

SEA-FISHERIES LABORATORY.

353 ■

added the figures for the “ weight ” net in each of the
three examples above for comparison with the two surface
nets.

The August hauls give us practically the same
results. There were 16 double hauls, and if we omit one
that seems very exceptional in character, in 5 of these
the otter net had the largest catch, in 5 the stern net
caught more, and in the remaining 5 cases the catches
were equal. The average catch for the otter net is 0*27 c.c.,
and for the stern net 0*30 c.c., while for the weight net,
worked at the same time in a deeper zone, the average is
0*35 c.c.

Comparison of ‘‘ Funnel ” with Wide-mouthed Net.

As a further development of the experiments with
the “ Pulley-net ” described in last year’s Report, we
added, in ’09, canvas inverted funnels in front of most of
our nets in order to limit the intake of water, and
consequently the pressure on the net. The inverted
funnel, suspended by its narrower end and joining the
ring of the tow-net by its wider, reduced the opening of
the net from 14 to 5 inches. As various opinions had been
expressed as to what the result of thus reducing the
mouth of the net would be, one of the older type of simple
open-mouthed tow-nets was used constantly as a surface
net alongside the funnel net, with the result that the
latter invariably caught more, and frequently a great deal
more up to 12 times as much. The average of 30 double
hauls gives 1*52 c.c. for the open net, and 4’36 c.c. for the
funnel net — one to three nearly. Having satisfied
ourselves that restricting the opening by means of the
canvas funnel leads to a greater, that is a more representa-
tive, catch, we shall in future use funnels with all our
surface tow-nets.

354 TRANSACTIONS LIVERPOOI. BIOLOGICAL SOCIETY.

The criticism has also been made at the International
Council, we are told, that our two exactly similar surface
nets fishing at the same time and catching somewhat
different gatherings were probably one on the windward
and the other on the leeward side of the ship working
under very different conditions, and so could not be
expected to yield comparable results. We can at once
remove that objection by stating that that is not the case.
When working the surface nets the ship is put head to
wind and steams very slowly against any wind there may
be ; so there is no windward side, and the two nets in
question are worked from the stern, side-by-side, and are,
so far as can be ascertained, under similar conditions.

Old and New Nets.

In the last part of this Report we showed how
rapidly the meshes of the fine No. 20 silk became clogged,

Fig. 20. Mesh of No. 20 silk
when new, x 23.

Fig. 21. Mesh of same silk after use
in Nansen net for some months, x 23,

SEA-FISHERTES LABORATORY.

355

and liow the catching power of a new net diminished from
day to day. We figure here photographs, which have been
kindly taken for us through the microscope by
Mr. Edwin Thompson, of (fig. 20) the silk of a new net
before being used, and (fig. 21) with the same magnifica-
tion a piece of silk from an old net that had been used for
some months. The flattened and swollen condition of the
fibres, the distortion and reduction in size of the meshes,
and the absolute closing up of some of them is obvious,
and accounts clearly for the reduced straining power of
the net.

CONCLUSIONS.

In the two preceding parts of this Eeport we have
drawn certain conclusions, some of which may now be
re-stated, and revised where necessary, in the light of the
third year’s work.

Total Plankton. — The most remarkable feature of
the distribution of the total plankton throughout the year
is the great increase in spring, due mainly to the sudden
appearance of enormous quantities of Diatoms. This year
the vernal maximum was later than in the two previous
years. It extended from April far into May, and died olf
suddenly between the 24th and the 28th of May.

There is usually a second less marked and less
constant increase in the plankton in September-October.
It is largely composed of Copepoda, although some
Diatoms, and on occasions Dinoflagellates in quantity,
may also be present. There may be lesser elevations in
June and August, due sometimes to one organism or to a
small group; but as a rule there is a period when the
plankton is reduced to a minimum in mid-summer and
another in mid-winter.

356 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

Phyto-plankton. — If, as is customary, we group the
Dinoflagellata (with, on the whole, a holophytio method of
nutrition) along with the Diatoms, the phyto-plankton so
constituted may he contrasted with the zoo-plankton in
several respects. The Dinoflagellata have usually one
well-marked peak or maximum in the year, and that lies
somewhere between the extremes of April and August.
Consequently the Dinoflagellates may be regarded as the
characteristically summer phyto-plankton. The Diatoms,
on the other hand, show two distinct maxima in the year
— in spring and in late autumn, with usually a summer
depression between. It thus seems that the conditions
prevailing in summer (Tune, July and August) are
unfavourable to a profuse development of Diatoms.

Winter is also unfavourable, and as a rule the period
November to March shows the greatest reduction in
phyto-plankton.

These results agree, on the whole, with those
obtained by Lohmann in the Baltic, but his autumnal
maximum of phyto-plankton seems to be greater than
ours. The Dinoflagellate Ceratium tripos, according to
Lohmann, begins in J une, reaches its maximum in
August and remains until October or November. With
us this species is usually present all the year round,
reaches a maximum in April to June and, with a few
depressions, remains fairly high until August.

The spring Diatom rise began later and ended later
this year than in the previous two years, and it is
interesting to notice that our hydrographic observations
in the Irish Sea show that both the temperatures and
salinities were lower than usual this spring.

Zoo-plankton. — Changes in the volume of our zoo-
plaiikton are almost entirely due to Copepoda, of which
fhe most abundant forms in our district are Oithona,

SEA-FISHERIES LABORATORY.

357

Pseudocalanus and Acartia. The occurrence of these at
Port Erin does not quite agree with that recorded by
Lohmann for the Baltic. For example, Oithona is
essentially an autumn form in the Baltic, and its
maximum is in October and November. With us it is
more constantly present, and may appear in quantity in
various months ; large numbers have been taken in
January, July and August, as well as in October. Acartia
also seems more widely spread with us, but our maximum
in June to July probably corresponds to Lohmann’s
maximum in May. Pseudocalanus with us appears in
quantity in October, and also in May- June, but is
apparently not a conspicuous form in the Baltic.

On the whole, the Copepoda have their greatest
abundance with us in early summer (May and June), and
again in autumn (September). They were most depressed
in ’07 and M9 during February and March, and in ’08
during January, February, July and August. There is
usually a marked drop in the Copepoda about mid-
summer, and this is sometimes followed (in July or early
August) by a vast swarm of one species, such as Calanus
lielgolandicus.

As a rule the Dinodagellate maximum in early
summer is later than that of the Diatoms, but precedes
that of the Copepoda. In the case of the less-marked
autumnal maxima there is less constancy and less regu-
larity in the order of succession.

Some organisms show a remarkable regularity in
their time of appearance. For example, the nauplii of
Balanus began to appear on February 22nd in ’07, on
February 13th in ’08, and on February 6th in ’09. This
is one of the cases where it is clear that the normal
sequence of events in the life-history of the organism is
the dominant factor in determining the constitution of

358 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY.

the plankton at a definite time and place — the periodic
reproduction of the Balanus causes the nauplii to appear
in the plankton at a certain time.

Many other swarms of neritic, and especially mero-
planktonic, forms (such as crab zoeas and fish eggs) are
similarly due to the succession of stages in the life-
history ; but oh the other hand, swarms of oceanic forms
may be due to immigrations caused by unusual hydro-
graphic or “ weather ” conditions. It does not seem
possible, as yet, to determine the effect of the various
factors — e.g., life-history and environmental conditions —
in producing and terminating the great maxima, such as
that of the Diatoms in spring. But we have given some
evidence in favour of the view that increase in sunlight
rather than any rise in sea-temperature precedes the vernal
maximum of phyto-plankton.

The most populous zone in the sea is below the
surface, but above 10 faths. The weighted net, ranging
down to about 10 faths., usually gives larger hauls than
the surface ones used at the same time. The organisms
in this zone no doubt rise and fall to some extent as a
result of weather conditions. Copepoda swarm on
occasions at the surface, and on other occasions are more
abundant a few fathoms below the surface. Diatoms,
when present in abundance in spring, are sometimes
found in increasing ratio from the surface down to
20 faths.

Certain organisms seem to be frequently distributed
in shoals. This is, of course, normally the case with
many larval forms, but is also common with, for example,
Calanus, Anomalocera, Temora, and probably Micro-
calanus. We have referred above to certain large shoals
of Calanus^ and to an occasion when an unusual quantity
of fish eggs was obtained from one spot.

SEA-FISHERIES LABORATORY.

359

In Port Erin Bay the organisms are on the whole
chiefly neritic, the percentage of oceanic forms ranging,
during the three years, from 30% to 60%. Mid-winter
(December and January) and mid-summer (July) are
markedly oceanic in character. The oceanic forms,
although not always the most abundant, constitute the
more permanent element of the plankton.

Fish eggs are commonest in the bay in March and
April, the maximum occurring in April. They occur
before that, rarely, in January and February, are present
afterwards in fair numbers in May and June, decrease in
July and August, and finally disappear in the beginning
of September. The greatest haul was 258 in the coarse
net on April 13th.

The catches inside Port Erin Bay give usually a very
correct indication of the plankton in the open sea. Our
numerous catches taken outside in spring and autumn do
not differ much from those taken in the bay at the same
fime.

For conclusions as to the work of the different nets,
and other details, reference must be made to the pages of
the report above.

C. Tinling & Co., Ltd., Printers, 53 Victoria Street, Liverpool.

m

/ •
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