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Report

of

The Danish Biological Station

1902 ana 1903.

By

C.. G. Joh. Petersen,

En D:

Translated from Fiskeri-Beretningen for 1903— 04.

Kjøbenhavn.
Centraltrykkeriet.

1905.

CACA
SÆT DY

g LØR oOo

23 P

LÅ LIBRARY 43

From

The Danish Biological Station

DET

1902 and 1903.

Kjøbenhavn.
Centraltrykkeriet

1905.

Cromtemnies

Page
I. Where, and under what Conditions, can the Eggs of Plaice be developed into Young

Fishswithinsthe "Skaw?" "By CGETTOREBeter sen Er Er — 3
II. On the Young Stages of the genus Zeugopterus. (With one Plate). By C. G. Joh.

Petersen SEE EEN EEN er eN N 25
III.

Can we enter into Competition with the Foreign Steam-trawlers in our Seas outside
the Danish Territorial Limit? By C. G. Joh. Petersen

E

Where, ånd under what Conditions, can the Eggs of
Plaice be developed into Young Fish within theSkaw?
By C. G.. Joh. Petersen.

Contents. El

1 18 ROY RELELA KO) Da SEN EOS EG AESER EET TEE ER ERE RER 3—4
On the Stock of Plaice in the Cattegat, the Belt-Sea, and the Baltic Sea

ERNST SEE ES DE LEES SES EEN SEES SEE ETS REE erne rENEE LE 4—6
he Dis butiongor ther Erysaloneither shore Er 6—16
What are the Causes of the peculiar Distribution of the Fry? ..........….. 16—19
What may be concluded from the Distribution of the Fry with respect to

tlesRenewvaloksthes SboCER ENES SREEN E eres srere aser ere SrETE 19—20
Some General Remarks on the Distribution of Various Species of Fish, as

Buy ssndsast Grow pE Bis Da ERE rare re (el aled serie tere sensorer SEERNE 21—23

What ought to be the Particular Object of Future International Investigations? 23—24

Introduction.

Twenty years have passed now since VW. Hensen published his original
and beautiful studies on zhe eggs of the plaice in the western part of the
Baltic Sea, and it is some ten years since I started the question of the oc-
currence of the fry of plaice on the Baltic shores. But not till these last
years have any new data been published, which throw light on the question
whether the plaice is able to live through its whole development, from egg to
grown-up fish, im the various parts of the Baltic Sea. Not till now, therefore,
we can begin to form an opinion on such questions as: In which regions
is it possible? Is it possible every year? To which extent may it be sup-
posed to contribute towards the preservation of the whole stock in the
various places? These questions are not by far solved as yet; they have
been set forth only with greater precision. 'The whole matter still deserves
renewed investigation, if it is to be of that use to practical fishery which a
close understanding of it seems to promise. Therefore it has been taken
up also for international investigation in "Commission CU” for the investigation
of the Baltic Sea.

4

1 "Abhandlungen des deutschen Seefischerei-Vereius”, vol. VII, 1902,
Schiemenz writes about the fishes from the Holsatia's cruise in the Baltic
Sea. In "Wissenschaftliche Meeresuntersuchungen, Neue Folge”, vol. VIIE,
Kiel 1904, C. Apstein writes in "Junge Butt (Schollen, Pleuroneectes platessa)
in der Ostsee” about the young plaice which of late years have been gathered
on the shores near Kiel. In '"Wiss. Meeresunt., Neue Folge”, vol. VI, Heft I,
1904, Ehrenbaum and Strodtmann write about "Eier und Jugendformen der
Ostseefische””, gathered as pelagic eggs and young fish on the Poseidon's ter-
minal cruises in the Baltic, and A. Kriger, ultimately, writes sTiber die Ver-
breitung junger Schollen an der deutsche Ostseekuste 1903”, "Mitt. des deut-
schen Seefischerei-Vereins”, No. 12, 1903.

These four publications, which are all closely connected with "The Inter-
national Exploration of the Sea”, give a report also of what has formerly been
published about these matters, more particularly the works of Elrenbaum
and Strodtmann. I shall refer to these publications, therefore, and here only
try to give a brief summary of the main points of the whole matter, and
to state what is known already, basing my statement partly on these pub-
lished papers, partly on unpublished investigations of the Danish Biological
Station. Finally, I shall mention certain facts to which we ought to pay
particular attention in future, if we want to gain a clearer insight into the
matter.

To avoid misunderstanding, I shall premise the observation that the
«Baltic Sea”, here, stands for the waters south of the Danish islands and
eastward; the "western part of the Baltic Sea” for the waters south of the
Danish islands as far as the line Gedser-Darserort; the "Baltic Sea proper”
is the sea east of this line and south of the isle of Saltholmen, near Copen-
hagen; while the "Belt-Sea” stands for the waters around Samsø, the Great
and the Little Belt, and the western part of the Baltic (Cmp. the map, p. 8).
These limitations I have already used for many years, for hydrographic-
biologic reasons, and I consider them, in this respect, suitable and Teton;
sible. (Cmp. ""Kanonbaaden »Hauchs« Togter”.)

On the Stock of Plaice in the Cattegat, the Belt-Sea,
and the Baltic Sea proper.

If we will take some pains to catch plaice of different sizes in the
Cattegat, as a rule also in the Belts, partly by employing fishing-apparatus
with small meshes, partly by fishing on deep as well as on low water, it
will be proportionally easy to get them in great numbers and of sizes like
those represented in table I, columns I & II. We see here, among others,
the smaller ones, the fry of the year (the 0-group), 1—c.4 inches (2"/,—eC.
10 ctm.) in length, in great numbers. These little fish are caught on low

Tabel I.

Colonne I Kattegat (Djursland). Colonne II. Store Bælt. Colonne III. The Baltic.
8.—10. Septbr. 1902. 0—10 Fathoms. k: End of August and in Septbr. 1901 and 1902. 2.—5. Septbr. 1902. S. E. of Møen. O—ca. 14 Fathoms.
Boned AU told: 874 Plaice. SÅR: Al told; 1748 Plaice. All told: 2384 Plaice.
16 É
== (9) All told: 865 Plaice. ad All told: 1519 Plaice.
Dan. Inches, Dan: Inches,
14 14 14
13 s 18 18
12 12 12
1 Å 1 1
10 10 10
9 9 . 9
8 s 8
É 7 7

75

DO Group d

The horizontal lines indicate the number of measured Plaice. 1 Millimeter indicates 1 Plaice.

To be bound between pg. 4 and 5. Report XII, Dan. Biol. Station 1 Dan, inch + 26 Millimeter.

- vre
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(ub 1

water, on the shores, where the latter are sandy and have not too much
vegetation, and are not too exposed to the direct dashing of the waves.
Where the dashing of the waves is too heavy, the sand is often coarse and
barren; but where there is some shelter, and the particles can remain among
the grains of sand, there the small plaice of the 0-group prefer to live. The
growth of the preceding year, however, the I-group, which in the autumn
is c. 4—7 inches (c. 10—18 ctm.) long, is also frequent. It is partly found
together with the 0-group on the sand, though as a rule on deeper water.
Where there are stones and a rich vegetation, as, for instance, 7» the Belts
on 2—7 fathoms, it may often be troublesome enough to catch this group,
because the fishing-apparatus (Petersen's trawl or English trawl with small-
meshed codend) is apt to take hold of stones or be filled with plants. That
it can be done, however, is shown by table I, column II. In the Cattegat
it is, as a rule, owing to the conditions of the bottom, easy enough to catch
the group in great numbers. In the following groups, II & IN, which I
shall not here make the subject of any closer examination, several of the
largest specimens, from c. 10 inches (c. 25 ctm.) and upwards, åre grown-up
fish. But as a whole the group between 7—14 inches (18—37 ctm ) cannot
be looked upon as the grownup group properly so called. This is missing
in the tables as a particularly pronounced group, and probably also in
nature. If, on the other hand, we go down into the Baltwe Sea proper, for
instance into the sea outside the isles of Falster and Møen, and try to make
a similar arrangement of all the groups there, by fishing from the shore
where there are splendid sands, seemingly well suited to be the dwelling-
place of the O-group, and out on the deep sea, then we get quite another
picture (Cmp. table I, column Ili). Here the stock consists, almost exclu-
sively, of a group of really grown-up fish, the males from c. 5 inches (c. 13
ctm.) and upwards, and the females from c. 5!/, inches (c. 14 ctm.) and
upwards. In spite of all seeking for small fish, both on the deep and on
the shallows, we have succeeded in getting only very few specimens which
may be supposed to represent a 0 and a I-group. The females of the
grown-up group have here very large ovaries and are furnished with white
rings around the red spots (Pl. borealis). See "Publications de circonstance
Nr. 1. Conseil permanent international pour 1'exploration de la mer”. It
was impossible, in the month of September, to determine the maturity of
the males, but this has been done on other occasions; these also have
white rings.

That the smaller plaice could not have escaped us if they had been
living in this part of the Baltic, is proved by the fact that we caught many
other small fishes, both flounders (P/. flesus) and common dabs (Pl. limanda);
the small flounders on the shores in shrimp-nets and ammodytes-seines, the
small dabs on the deep sea. There is no doubt that the small plaice of the
O-group and the I-group were rare in these seas, not only compared to the
large number of grown-up fish, for these are here more numerous than any

where else on the shores of Denmark, and only near Iceland have I seen
them in such numbers; but also absolutely considered the 0-group was
rare, as the time spent on these investigations has often shown me.

Something similar to this has been the case also in other years, as may
be proved by a reference to the "Report of the Danish Biol. Station, IV,
1893”, tables VII & VIII (from the the same seas and from the isle of
Bornholm), which show that only 3 plaice under 13 ctm. were caught at
Bornholm, but a great many over; and at the isle of Møen none at all
under 8 ctm. Table X, loc. cit., on the other hand, shows many flounders
as small as 1!/,—2 ctm. at Bornholm.

These remarkable differences in the occurrence of the fry (the groups
0 & I), its frequent occurrence in the Cattegat and, partly, in the Belt-Sea,
and its rarity in the Baltic Sea proper, have from the beginning seemed to
me to be of the greatest importance with respect to the renewal of the
stock. The scarcity of the fry on all the Danish shores of the Baltic Sea
during the years in which I investigated the matter, also on the shores of
the western Baltic Sea, made me suppose that the fry was scarce, also on
the corresponding German and Swedish shores from which we had no infor:
mation. I had so much the more reason for this supposition, as it was
directly supported by the investigations of Apstein in August 1893 (loc. cit.
p. 3), who found, near Eckernfårde, only one young plaice, but 153 flounders.
Later investigations on the German shores have proved, however, that a
great number of small young plaice, in certain years at any rate, are found
on the shores from Eckernfårde to Warnemtinde; hut very few have been
Jound east of the Line Gedser—Darserort. On the shores of Bornholm I
myself and my co-workers have in certain years taken some specimens;
also, but very few only, on the shores of Falster and on deeper water S. E.
of the isle of Møen (See p. 4, table I, column III, 1902). The Holsatia
found one specimen, 2 ctm. long, on deep water; but Schzemenz himself
writes after his expedition in the Baltic: "Auffallend ist, das der erste Jahr-
gang (mit einer Ausnahme) vollkommen und auch der Anfang des 2. Jahr-
gangs fehlt. Dies stimmt also gut mit Petersens Anschauung tberein'.
IR pæls0:

The Distribution of the Fry along the Shores.

In 1902 Johs. Schmidt, on board the Biological Station's steamship
Sallingsund made a very close investigation of the Danish shores for the
purpose of studying the distribution and numerousness of the fry of plaice.
His results are given below.

«The distribution of the fry of the year (the 0-group)" was investigated,
particularly in the months of June and July, 1902, on the shores, on low

water, with shrimp-nets (one of bobbinet, with very fine meshes, another
with more open meshes, 9mm from knot to knot), and nearly always by
wading with the nets, i. e. when the water was sufficiently low; which was
generally the case in all places where the fry of the year occurs in this
season. The places which are specially suited for the occurrence of the fry
of plaice are flat sand-banks with shallow water (2—3 feet), which can be
heated through by the sunbeams, and with a clean, sandy bottom without
any vegetation and without any great interspersion of organic substance. In
places where the shore was so steep that it was impossible to wade, we
made use of a shrimp-net from the jolly-boat, kept in place by a man in
the stem, while another man was rowing. In this way we sometimes
caught pretty much, though never so much as when we were wading, when
it was much easier to give the apparatus the suitable speed, so that none
of the larger and quicker young plaice could escape. Later in the year, in
the end of August and in September, we also employed, now a hait-seine
with very small meshes, now a small-meshed ammodytes-seine ("inch-seine””) for
the catching of young plaice. From these investigations, the results ol
which are partially to be seen on the map, p. 8 and table II, we learn
more particularly the following.

On the Occurrence of the Fry on the Sea-shore on Low Water.

On the Shores of the Cattegat we found the fry of plaice everywhere
where we were looking for it, except where too much fresh water from
rivulets is intermixed. In such cases it is replaced by the fry of flounders,
for instance at the mouth of Mariagerfjord where, otherwise, the bottom
is excellent for the fry.

In the Little and the Great Belt together with the adjoining seas (the
archipelago south of Funen and the Langelandsbelt) the fry is found every-
where in suitable places, with the sole exception of Marstal Sande where,
moreover, the fry of the year of flounders is not found either. If we now
go eastward to Smaalandshavet, the number of the fry decreases. At Fejø
… we found c. 25, at Glænø some few, at Knudshoved 1, and farther eastward
none at all, neither in Grønsund nor Ulfsund. At Rødsand and S$S. of the
isle of Møen") at Klintholm harbour there were excellent sand-banks, but
not one young plaice was found here, nor did we find any on the northern
shore of Møen, in Faxebugt, Køgebugt, or on the shore of Amager. We may
say, therefore, that the fry of plaice was missing im the Baltic Sea proper
and in the southern part of the Sound. We meet it again in he northern
part of the Sound, from Strandmøllen, but here as well as more northward
in the Sound in small numbers only.

The Isefjord.. The fry is found here only just at the mouth of the
fjord; higher up in the fjord it is quite missing. This is the case perhaps

1) Off Bøtøgaard, in South-Falster, on the 4. Septbr., we caught a young plaice,
38 inches long, on 1Y, fathom of water.

in all the fjords, corresponding to the state of things in the Great Belt —
Smaalandshavet — Eastward, where the salinity is decreasing just as in the
Isefjord.

The size of the fry of plaice may be very different in the various
localities at the same time of the year (Cmp. table II). This is particularly
striking at two places situated so near to one another as Fænø in the Little
Belt and Baaringvig. At the former place the fry is grouped round 15 mm,
at the latter round 35, though the gatherings have been made on the same
day. The said example is the most striking, but several others show some-
thing like it, as may be seen from table IL.

In some localities the seize of the fry has been investigated on the same
spot, at various times of the year, in order thus to get an idea of the average
size of the growth. I shall here give two examples.

Hevringholm (N. of Djursland. — Stations 3 & 37, table IM). The 19.
of June the average size of 124 young plaice was 25 mm (i. e. the largest
group were 25 mm). The 8. Septbr. we caught on the same spot 335
young plaice, the largest group of which were 60 mm. The young plaice
had then grown, on an average, 35 millimeter, from June 19.-—September 8.,
i. e. in 80 days, or, if we suppose the growth to be uniform in these sum-
mer months, ”'/, mm a day, consequently a little less than half a milli-
meter a day.

Holckenhavn (Nyborg Fjord). (Stations 10 & 14, table IN). Here we
find from July 7.—Aug. 21. a growth from 25 mm—50 mm, or 25 mm in
45 days, i. e. a little more than half a millimeter a day.

While all the hitherto mentioned young plaice of the 0-group have been
taken on the shores, on low water with sandy bottom, we succeeded, in the
beginning of September 1902, to prove beyond doubt the occurrence of
specimens of the 0-group on deep water, 10!/, fathoms, in the Baltie Sea,
viz. S. of the isle of Møen with Hestehoved N.”/, W., on hard, sandy bot-
tom witb Mytilus, where they were caught with Danish trawl in a number
of 16, together with specimens of the 1-group and older plaice, as also one
young flounder of 24 mm and one young common dab of 30 mm. In this
connection I shall mention that I, on the 23. of July 1902, caught a young
plaice of scarcely 2 inches, on Kriegers Flak (9—10 fathoms, Møens light-
house in W."/, S., Mytilus bottom).”

Johs. Schmidt gives here a good picture of the occurrence of the fry
of plaice in 1902 — a year which seems to have been favourable to the
growth of this fry — and the picture becomes clearer when we look at the
map, p. 3, where all the numbers of the stations at which this fry was
found are marked with figures, while the places where the fry was not
found in the time from June—Septbr. are marked with a 0. In 1902 we
found no 0-group before June. In 1893 it was found already on the 30.

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April near the mouth of the Limfjord in the Cattegat, but in small num-
bers only, and in the middle of May at Frederikshavn. In. 1903 it was
found at Esbjerg, by 4. C. Johansen, already in the month of April; all
these 4 places as very small fish, 1—2 ctm. in length, and it seems, con-
sequently, that it appears on the shore a little earlier in the northern Catte-
gat and in the North-Sea than in the Belt-Sea. The small specimens
at Schmidt's stations 4 & 7 show that we have here to do with quite re-
cently transformed fish.

In order to give as much information as possible, also about the guan-
tity or frequency of this fry at the stations that were investigated in 1902,
I shall here give a copy of the journal kept by Johs. Schmidt on board the
Sallingsund. The reader will then be able to judge for himself 1) of the
time and labour bestowed on the investigation at the various places, also
where no fry was found, and 2) through this, about the frequency of
the fry.

«The Cattegat.

Saturday, June 14., 1902. (At Frederikshavn, at 2,45 0'clock). Out with
the jolly-boat on the sand N. of the harbour to catch young plaice. With a
shrimp-net with fine meshes several hundred were taken in the course of about
half an hour. One haul of c 30 m. in length gave 63 specimens.

Wednesday, June 18., 1902. Caught fry of plaice on the sand S. of Asaa
pier, in the morning, with a shrimp-net with fine meshes. There were not by
far so many as at Frederikshavn; the greatest number we ever got in one haul
was only 8.

Thursday, June 19., 1902. Tried to catch fry of plaice on the large plains
of sand at the mouth of Mariager Fjord, but there was none at all.

At 11,15, at anchor off Hevringholm. From 11,30—12,30 we caught fry
of plaice on the sand-banks along the shore; fine, clean, sandy bottom with
fucus bushes. There were many plaice (as many as 12 in hauls of 30 meters),
though not so many as at Frederikshavn. Besides the fry of the year we got
here in the shrimp-net about 20 specimens of the I-group.

The Little Belt.
Tuesday, June 24., 1902. Fænø in Lillesund, at 5 p. m. With shrimp-net
c. 100 were caught at Fænø N. of Espenhoved, mostly very small plaice.
Wednesday, June 25., 1902. Left Fænø at 6 a. m. Caught fry of plaice
with shrimp-net on the sand-banks in Baaringvig. Found both plaice and
flounders. There were here many plaice (c. 10 in one haul).

The Great Belt.

Kerteminde, at 5,30 p. m. Caught fry of plaice with shrimp-net on the
sand, straight N. of the harbour. There were many plaice; 6 score in 20 min-
utes with a common shrimp-net.

Thursday, June 26., 1902. The little bay at Slipshavn (Nyborg) was searched
with shrimp-net for fry of plaice. Only one plaice was found.

To Nyborg — — Under Holckenhavn. Investigated the fry of plaice with
shrimp-net under Kajbjerg Skov, on the sand-banks. There were rather many
young plaice (7 score in scarcely 1 hour, with 1 shrimp-net); but nearly all
of them were smaller than at the other places where we have been this year.

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The Baltic Sea.
Thursday, July 3., 1902. Left Gedsergaard at 8 a. m. Searched Rødsand
E. of Vesterholm) with shrimp-net and hait-seine for fry of plaice; there were
no young plaice.
The Great Belt.
Friday, July 4., 1902. We investigated the fry of plaice with shrimp-net
on the sand-banks on the N. shore of Fejø. Found c. 30 plaice of the 0-group.
Searched the sand-banks on the east-side of Omø, S. of the telegraph mark,
with shrimp-net for fry of plaice. There were a few plaice of the 0-group.
Monday, July 7., 1902. Searched the sands at the bhath-house of Holcken-
havn with shrimp-net for fry of plaice. In the course of 1 hour c. 30 plaice
were caught.
Tuesday, July 15., 1902. Out at 8,35 a. m. Searched for fry of plaice
with shrimp-net on low water:
1) S. of Lundeborg. We found here c. 5 specimens in each haul, both
flounders and plaice of the 0-group.

The Southern Part of the Little Belt and the Western Part of the Baltic Sea.

2) Thurø Rev. Exceedingly many plaice of the 0O-group (large, 1—2”).

3) Iholm, Svendborg Sund. No sandy bottom.

4) Within Lensskov. Very poor result. 5 plaice of the 0-group. In Faa-
borg at 4 0'clock p. m.

Wednesday, July 16., 1902. Left Faaborg at 6 a. m. Investigated the fry
of plaice with shrimp-net on low water:

1) Drejø. In the course of 1!/, hour we caught with 2 shrimp-nets c.
20 plaice (c. 1”). Moreover a few plaice of the I-group were caught.

2) Urehoved (Ærø), on the N. E. side. In a little more than half an hour
we caught with 2 shrimp-nets only 6 plaice of the fry of the year.

3) Sæby Bugt (Ærø). Good sand-banks. Not many plaice of the 0-group,
though more than at Urehoved. C. 12 specimens in 20 minutes.

4) Vorbjerg (W. shore of Ærø). The shore too steep for wading. Tried
to row with the shrimp-net on one fathom of water and got in the course of
about a quarter of an hour two plaice of the O-group.

Friday, July 18., 1902. Yesterday evening, wading with shrimp-net, we
investigated the fry of plaice on the large flat sand-banks W. of Dyreborg.
With 1 net we caught c. 30 plaice in 20 minutes.

Fry of plaice with shrimp-net: off St. Albani Churchyard, on the W. shore
of Ærø. The shore was too steep for wading. A very small area was flat,
and here we made a few hauls, but found no plaice.

Marstal Sande at Langholm. There were here large flat sand-banks with
clean sand and fresh water, consequently seemingly good conditions for the fry of
plaice. Nevertheless not one young plaice of the O-group was found, though
we fished for about one hour.

At Bagenkop, 1 0'clock p. m. Searched some sand-banks N. of Bagenkop
harbour with shrimp-net. Found, in 20 minutes, only 2 young plaice (0-group).

Off Holmegaard (Langelandsbæltet). Looked for fry of plaice with shrimp-
net. The shore too steep for wading, Fine sandy bottom. Fished with
shrimp-net from the jolly-boat. In the course of half an hour we got 4 plaice
of the 0-group.

Gottesgabe (S. Laaland). Looked for fry of plaice. The shore was also
here too steep for wading. With shrimp-net from the jolly-boat we found in
half an hour 2 plaice of the O-group.

Albuens Havn. Investigated the fry of plaice with shrimp-net. There were

no real sand-banks, but just on the edge of the sea-shore there was a narrow
belt of gravelly sand where we could wade. In the course of about 1 hour
we found c. 6 plaice of the 0-group.

The Great Belt.

Saturday, July 19., 1902. Imvestigated the fry of plaice with shrimp-nets:

1) On the sands south of Spodsbjerg... Good sand-banks. There were here
exceedingly many plaice; in 10 minutes we got c. 50 with 1 shrimp-net (c. 20
in one haul of 15 meter).

2) At Hov Sand. Less good bottom; nevertheless c. 5—6 in short hauls.
In the course of half an hour c. 30 plaice of the 0-group.

Monday, July 21., 1902. Investigated the fry of plaice on the east-side of
Agersø. Good sand-banks. In the course of 20 min., 13 plaice with one net,
all of the 0-group.

Tuesday, July 22., 1902. Investigated the fry of plaice with shrimp-net off:

1) Glænø Vesterfed.… Good. sand-banks. In the course of about half an
hour we caught, with one net, only 1 plaice of the 0-group.

2) Gumperup Klint. Wading impossible. No plaice; but the investigation
was difficult on account of the steep shore.

S. of Zealand.

3) The south-side of Draget Knudshoved. Owing to high water only a very
small area with good sand-banks could be investigated. In a good half-hour,
with 1 net, 1 plaice (2”) of the 0-group.

4) E. of Orehoved ferry-harbour there were no sand-banks.

5) Masnedø Kalv. No sand-banks.

6) Lilleø (between this and Tærø). Flat areas with sand-mixed gravel and
spots of characeæ. No fry of plaice.

7) Koster, E. of the ferry-harbour. Gravelly sand. No plaice.

8) Off Farnæs forest. Gravelly sand with characeæ. No plaice.

The Baltic Sea proper.

Wednesday, July 23., 1902. Left Stubbekjøbing at 7 o0'cl. a. m. Looked
for fry of plaice with shrimp-net:

1) Just W. of Stubbekjøbing harbour-mole, on pretty good sandy bottom.
No fry of plaice.

2) At Grønsunds Hage. No sand-banks.

3) Off Næsgaard. There were here several good sand-banks. We fished
for half an hour, but found no plaice.

4) W. of Kyintholm harbour (Møen). Splendid large sand-banks in fresh
water. Investigated the inmost bank for half an hour with shrimp-net, but
found no plaice.

Thursday, July 24., 1902. Investigated the fry of plaice with shrimp-net:

1) On the east-side of U/fshage (Søhunde harbour). There were splendid
large sand-banks. In 15 min., with 1 net, we found no plaice.

2) South of the leading lights on Præstø Fed. Splendid sand-banks. In
20 min. we caught no plaice.

3) N. of Faxe harbour (the northmost). Good sand-banks. In 15 min.,
with 1 net, we caught no plaice.

4) At Kjøge Sønakke. On most sand-banks the water was too deep for wading.
With shrimp-net from jolly-boat, and wading with shrimp-net on a little sand-
bank, we caught 1 turbot and 1 flounder.

We also tried at Stevns, N. of the lighthouse, but the water was here too

deep for wading; we then tried a haul with hait-seine, but got only some
gobies.

Friday, July 25., 1902. Left Kjøge at 6 a. m. Investigated the fry of
plaice with shrimp-net:

1) On the east-side of Aflandshage (Amager). No proper sand-banks with
low water suitable for wading. With shrimp-net we caught from the jolly-boat,
on somewhat deeper water, a couple of flounders.

The Sound.

2) North of Kastrup harbour (Amager). Nothing was found.

3) Just N. of Strandmøllen (in the Sound). The water was here too deep
for wading on the banks, but with the shrimp-net from the jolly-boat we
caught in 20 min. 5 plaice of the O-group.

4) Off Sophiehøj (N. of Vedbæk). There were here pretty good sand-banks
on which we could wade. With 1 net we caught in 25 min. 7 plaice of the
0-group.

Saturday, July 26., 1902. From Elsinore at 8 a. m. Investigated the fry
of plaice with shrimp-net:

1) N. of Nivaa brick-works. Good sand-banks. With 1 net in 20 min.
23 plaice of the O-group.

2) Off Julebæk forest. Good sand-banks. With 1 net in 15 min. 3 plaice
of the 0O-group.

The Isefjord.

Wednesday, July 30., 1902, From Elsinore at 6 a. m. Investigated the
Fry of plaice in Roskildefjord with shrimp-net:

1) At Øæneholm. No fry of plaice was found.

2) Dyrenæs Hage. Good sand-banks. No fry of plaice.

3) N. and S. of Frederiksværk. Good sand-banks No fry of plaice.

Thursday, July 31, 1902. Left Frederiksværk at 7,30. Investigated:

1) Hønsehalsen. Good sand-banks. No fry of plaice.

2) Hølkerup. Good sand-banks. No fry of plaice.

3) Skansehage (off the hospital). Good sand-banks. In 20 min. we caught
c. 40 plaice of the 0-group

The Great Belt.

Friday, August 1., 1902. Left Nykjøbing at 515 a. m. Investigated the
fry of plaice with shrimp-nets on the north-side of Sejrø off Kongshøj. The
breakers on the lowest sand-banks made wading impossible. We worked for
half an hour with the net from the jolly-boat and caught 5 plaice of the
O-group.

Tuesday, August 26., 1902.

The 0O-group of the plaice is found on the sand-banks on low water 5. of
Lundeborg.

A number of plaice, which must be supposed to be one year old, were
found off Lundeborg, most of them on deep water (9 fathoms), on the oozy
bottom, together with common dabs; a few also on the sand-banks on low
water. Such plaice, then, seem here (and in Nyborg Fjord) to live under very
different conditions.

Thursdag, August 28., 1902. North of Kjerteminde harbour on 2 fathoms
of water: I. A number of plaice of the O-group were taken on the sandy bot-
tom with shrimp-net. — II. With bait-seines we made some hauls towards
land. Of flat-fishes (plaice and flounders) we took -altogether 8 score (2 score
in the haul).

14

The Baltic Sea proper.

Thursday, Septbr. 4., 1902. Left Gedser at 5 a. m. Investigated the sea-
shore off Bøtø-Gaard for fry of plaice, wading with shrimp-nets. 2 hauls with
inch-seine); one of them gave — 1 plaice, 3 inches long.

The Isefjord.

Saturday, Septbr. 6., 1902. At anchor off Skansehage, at 8,30: Fished with
shrimp-net on the shore, and with inch-seine. A few plaice were found on the
sands on the shore.

The Cattegat.

Monday, Septbr. 8., 1902. Off Rygaarde and Hevringholm. Investigated the
sand, from 1—6 feet, with inch-seine, bait-seine, and shrimp-net. Got many
plaice of the O-group and not a few of the I-group.

Wednesday, Septbr. 10., 1902. Fished north of Grenaa harbour from 6 till
7,15 a. m. with shrimp-net and inch-seine. 4 hauls with inch-seine from c. 1
to cc. 8 feet: 4 plaice.

Off Gaasehage (Helgenæs). Tried with a shrimp-net to find plaice on the
sand-banks. There was none.

The Belt-Sea.
Off Løghøj, Mols. Looked for plaice on the sand, with shrimp-net. Caught
in a short time 4 plaice.
Thursday, Septbr. 11., 1902. Off Maarup in Samsø. Only very small spots
of sand free from stone (on the sea-shore). 2 hauls with inch-seine from c. 2
to, 8 feet… 6 plaice.”

For 1903 we have, from Denmark, no such detailed investigations into
the distrihution of the fry of plaice as we have from 1902; but the fry
has been seen as far down as the southern end of the Great Belt, and when
we compare this with the results of the German investigations, the limits
for the occurrence of the fry must be supposed to have been about the
same as in 1902. At Bornholm I found no O-group at all, in spite of
thorough investigation. Elwrenbaum, in 1903, found the 0-group at Eckern-
førde, and Kriiger in Kielerfjord (Labåe), Traweminde, Warnemiinde, bud
mot at Riigen (Barhøft).

In 1893, as will be seen from "Report of the Danish Biological Station,
IV”, page 10, the occurrence of thé fry in the Cattegat and along the
shores of Funen and Zealand as far as Bornholm was investigated at some
50—60 stations. If we draw a line from Vejle in Jutland to the north-
most point of Langeland and from this place to Copenhagen (cmp. the map,
p. 8), all the stations where the fry occurred in large numbers are situated
north of this line. On the western shores of Funen it was very scarce,
and was found at one station only, although there are 3 stations here. At
Fænø in the Little Belt there was none; on the eastern shore of Falster we
found one, 2 inches long; and at Kjøge, in East Zealand, on the 16. of
August, we found two, 3//,—3"/, inches. At Bornholm we caught three, in
September, 2—23/, inches long (1. c. 105—108); Apstein, however, did not

]) i, e, a seine the meshes of which are 1 inch from knot to knot.

15

find any at Eckernfårde in August; on the other hand he caught 153
flounders. In 18953, the southern limit of the distribution of the fry, im June—
September, seems consequently to have been more to the north than im 1902.
The shores of Laaland, Falster, and Møen were investigated with particular
care in 1893, but we took here altogether only one specimen. In spite of
eager investigation at Kerteminde, where the "Biol. Station” was situated,
the fry of plaice was not found here on the sands till 1. June 1893, and
then already mixed with flounders as small as 3 mm in length.

These two years, 1903 & 1893, are those in which we made the most
detailed investigations. Of other years I shall give the following information.

In 1901 Dr. Th. Mortensen investigated Bornholm from June 26.—July
6., without finding any specimen of the 0-group.

In 1900, in June & July, the fry was found in the northern part of
the Cattegat and in the mouth of the Isefjord; at the latter place only in
small numbers. At Samsø only a few were found, and at Reersø in the
northern part of the Great Belt, in spite of eager investigation, only 2 spe-
cimens. At Laaland, in spite of eager investigation, we found none. I
still remember, distinctly, my astonishment at finding so few young fish
that year, as I had formerly caught many more in the Belt-Sea. I was
particularly desirous that year of pointing out where to look for the Aead-
quarters of the southern race with the smaller mumber of rays in the fins, but
wrote in my journal on board S. S. Sallingsund, the 21. of June, 1900:
«The result of our search for the 0-group this year seems then to be that
such fry is very scarce this year in the Great Belt and around Sejrø, though
there is a little everywhere, where there are the necessary natural conditions.
The head-quarters of the fry of the southern race must therefore, for the
present, be supposed to be on the eastern shores of North-Zealand and
Middle-Jutland.”

This year, therefore, seems to have resembled 1893 in this respect that
the fry only proceeded a short distance towards the south im the Belt-Sea.

Il have through these investigations got the decided impression that the
fry in the Belt-Sea is never so numerous as in the northern Cattegat, and
that its geographical distribution down there varies very much from year
to year.

We may be quite sure, however, that the fry of plaice of the 0-group
is found every year on the western shore of Jutland (in large numbers at
Esbjerg and Thyborøn); on the shores of the Cattegat towards west and
south (of Sweden nothing is known); and a longer or shorter distance down
into the Belt-Sea, sometimes as far down as the western part of the Baltic
Sea, west of Laaland and Femern, but only on the more open shores and
at the mouths of the fjords, never deep into the Limfjord or the Isefjord.

It is also most likely that the fry is not found in larger numbers, but
only singly, and especially towards autumn when it has grown a little larger,
in the seas east of Gedser—Darserort; but, certainly, from Germany we

16

have here only very few direct investigations, and from Sweden none at
all. It would be of great importance to get such in 1904 and the follow-
ing years.

I presume, however, that such investigations from other countries will
give results similar to the above mentioned, and several German investiga-
tors, Schiemenz, Ehrenbaum, and Strodtmann seem to have the same opinion.
But this must be confirmed by direct investigations carried on through
several years; and we must not be content with looking for the fry along
the shores in localities similar to those where it usually occurs. It is pos-
sible that the fry can live and develop itself on deeper water, as, for in-
stance, the fry of the common dab usually does. Certainly, I do not be-
lieve this to be the case; but we must be able to say that this possibility is
excluded by our direct investigations, as it is now, in my opinion, in the
Danish seas proper.

What are the Causes of the peculiar Distribution
of the Fry?

We all know that the plaice have pelagic eggs, and that the young
fish go through their transformation from young ones, c. 6—7 mm long,
just out of the eggs, till they become unsymmetrical when they are about
11—14 mm, and then go to live on the flat, sandy, sunny shores. As above
mentioned this takes place within the Skaw, in the months of May and
June. The eggs, on. the other hand, are shed from November (October,
Trybom) till some time in April; but most of them, certainly, in the depth
of winter ("Report of the Biol. Station, IV”). We know now, from earlier
times (Hensen, Petersen), these eggs with embryos from all open seas within
the Skaw as far down as into the western part of the Baltic Sea; and
Petersen has them from the Baltic Sea in large numbers, south of Møen, in
March 1902 and Februar 27.—28., 1903, on 12 fathoms' depth, with a sali-
nity of 17,4 %,, and 2,5? C. March 21., 1903, we searched for eggs again
in the same place, but now the salinity was only 10,6 "/,,, temp. 3,8? C.,
and no eggs were found. In February we had had violent western storms,
therefore, probably, the salt water; the latter together with the eggs dis-
appeared, however, in the course of March. On the expedition of the
Poseidon, in February 1903, eggs were also taken in large numbers in the
western part of the Baltic Sea, decreasing, considerably, in number towards
Bornholm; one is even stated to have been taken east of Bornholm, where
the salinity was only 13,73 %/,, on the bottom.

In all these seas we may also take plaice with ripe spawn and milt;
south of Møen I have caught them many times in huge multitudes, and
Trybom ("Svenska hydrogr. biol. Kommissionens Skrifter I", p. 10) found

17

them near Bornholm. There is no reason to doubt then that the plaice
produce fecundated eggs as far east as Bornholm, and perhaps still farther;
nor did anybody ever doubt it. But the question is: What becomes of these
eggs? Do they die away? Do they drift away? For of the huge multi-
tudes no corresponding quantities of fry remain in the Baltie Sea proper; at
any rate not of fry that has passed through all the pelagie stages, and stay
near the bottom.

OF pelagic young plaice only very few have hitherto been found east
of Gedser. The Poseidon's three expeditions in 1903 gave only 18 in the
Baltic Sea, against more than 200 flounders and common dabs together,
and personally I have, in 1903, found only very few pelagic plaice, but as
well east as west of Gedser. To throw more light on the quantity of these
larvæ, these investigations, therefore, must be continued in March—May
with suitable apparatus; the common pelagic nets are not well adapted for
the purpose. ÅA youngfish-trawl which I have constructed and employed already
for several years from the Sallingsund, has a far greater fishing-capacity.
Dr. Johs. Schmidt, who employed it with great profit in Iceland, 1903, will
in another work give a description and a picture of it. I shall here mention
only, that it is a sort of small otter-trawl made of cheese-cloth or ""stramin”,
whatever you will call it, and may be employed on somewhat deeper water,
in the very mass of water as well as near the bottom, to catch the fry be-
longing to the bottom-stage. !)

On the whole, there seems to be, in the pelagic life of the plaice, some-
thing which has hitherto remained unexplained. Its larger pelagic fry has
been found nowhere in very great numbers, not even near Iceland where
young gadoids and other pleuronectids have been taken in multitudes. Yet
we should suppose it must have a long pelagic existence, since the eggs
occur in the Baltic Sea already before the beginning of winter, while the
little young ones belonging to the bottom-stages are not to be found till
the end of spring.

Owing to this cirecumstance we cannot very well, at the present stage
of our knowledge, use the few finds of the pelagic fry of the plaice in the
Baltic Sea for quantitative determinations; for this purpose we had better use
the bottom-stages (the O-group), as they are found in great numbers in many
places, and as it is easy to catch them and determine them.

We do not know at all, for instance, if the 0-group which occurs in
the Baltic Sea in June, comes from eggs that are shed in the Baltic Sea.

7) As to the fishing-capacity of this youngfish-trawl I shall say only that, west of Ærø, in
the western part of the Baltic Sea, on 20 fathoms of water, May 15., 1902, on soft clay
bottom, I caught in one haul which lasted 10 minutes, more than 1000 young ones of
Lumpenus lampetriformis, between "/,—2 inches long, as also several hundred of two
larger groups, respectively 3—5/,, inches and 5'/,—8 inches long, besides some still larger
specimens. I had not known before that this fish is one of the commonest on deeper water
in the western part of the Baltic Sea.

3

18

There are people, perhaps, who have no doubt about it; but I cannot help
doubting, and I regret that I have not formerly been as consistent in my
doubt also with respect to the Cattegat, a fact to which Ehrenbaum and
Strodtmann, 1. c. page 123, justly call attention. For it is quite possible,
indeed, that the Cattegat does not get its main supply of young plaice
through fry of its own eggs, but that the greater part of the fry, perhaps,
comes from eggs shed in the North-Sea, the Baltic, or the Belt-Sea.

For one thing is certain, that the eggs in the long period before the
hatching, and the fry in the still longer pelagic period (from October till
May—June, as we may suppose for many of them), must be carried along
with the current — in most cases we scarcely know where. According to
my earlier investigations the eggs have such a specific gravity that they
can only float m water which at 10" C. has.a salinity of 14,4 %/,, or higher.
Hensen has found that somewhat higher salinities are necessary. But in
open nature I have often found eggs of plaice in water of c. 15%, and
Ælwrenbaum, 1. c€., thinks he has found such an egg at a salinity of 13,73 "7,
and a temperature of 4,57?; I do not, however, attach great importance to
this one egg. By my experiments I have shown ("Report of the Biol.
Station, IV”) that there is a considerable variation in the floating-power of
the eggs; but as a rule they will scarcely be found, I think, in water of a
salinity lower than c. 145%. They are able to float, consequently, only
where there is such water, and if they cannot float, I must suppose that
they die; for it is not very likely that they can be developed in the oozy
particles of the bottom, and if they only touch the latter, they will probably
be devoured in the course of a very short time by the animals that live there.

The existence and. development of the eggs is, consequently, only pos-
sible, where there is for some length of time water of a salinity of e.
14,5 /,, or higher. We do not know more exactly what salinity the pelagic
young fish require, what temperature, light etc.; but the very necessity of
a salinity of a least 145 /,,, through rather a long time, reduces the distri-
bution of the eggs considerably.

Il have before me a map of the Danish seas on which a number of
places have been marked down where pelagic eggs were not found at all
in the surface in March & April 1902, and other places where they were
found. These places, altogether c. 20, have been stated by Lieutenant C. J.
Hansen, R. N., a gentleman whose name is often mentioned, e. g. in "Report
of the Biol. Station, IVY. While in command of the schooner Argus, he
fished for pelagic eggs with a silk net of the usual form and size, in the
Belt-Sea, in the above mentioned months. If we draw on this map a line
from Cape Kullen to the southern point of Langeland, all the stations where
eggs have been caught fall north and west of this line; no eggs have been
caught south and east of the same. All these eggs were taken in the sur-
face. The said line is very nearly identical with the boundary line between
water of 10—14 %,, salinity and water of 14—21?/,, or higher salimity,

19

measured by aræometer on board the Argus; in fresher water no eggs are
to be found, in the more saline water they are found as it were always.
Doubtless, these eggs are not all eggs of plaice, but at several stations they
certainly are, according to my later determinations, and at any rate all the
negative results give certain information. Another map which lies before
me, based on our own investigations, in March 1902, into the occurrence
of eggs in the lower strata of water, shows, on the other hand, that eggs
of plaice are found in the deep water everywhere in the Belts as well as
in the eastern part of the Baltic Sea, as far as S. E. of Møen, under the
overlying fresher strata. But these deeper masses of water do not, as a rule,
reach the shores, and they do so more and more rarely the farther south
and east we go through the Belts into the Baltic Sea.

It is not my opinion that the line Cape Kullen—the Southern Point of
Langeland is constantly the boundary between the salinities of c. 14,5 9/9
and the lower ones. The line may go up or down, particularly the south-
western part of it (cmp. the fine maps of salinities in the publications of
«Kom. til vidensk. Undersøgelse af de danske Farvande”); but it marks
the territory near which we must look for this boundary line, and indicates
roughly the southern boundary of the territory where the fry of plaice be-
longing to the bottom-stage is generally found in large numbers on the
shores (cmp. map. I, page 8).

In the present state of things we must suppose, therefore, that the eggs
of plaice, which are found in the sea, presumedly, from the Skaw down into
the Baltic as far as Bornholm, as a rule, can go through all pelagic stages
to the bottom-stage, only where the water at certain times can lift them up in the
vicinity of the shores and thus carry the young fish to the low, light, sunshiny,
and warm eoasts which seem to be necessary for their development, wlale those
which remain in the dark, cold, low strata of the water im the Baltic Sea
proper, evidently, as a rule, are destroyed.

A close study, through several years, of the occurrence of the tender
fry on the shores, compared with the changing hydrographie conditions, will
therefore, no doubt, give very interesting information with respect to the
growth of the stock in the various years.

What may be concluded from the Distribution of the Fry with
respect to the Renewal of the Stock?

In the Cattegat, from the Skaw to a little south of Anholt, about 10—15
million plaice are caught yearly. In the sea north of Zealand and around
Samsø as far down as north of Funen only a comparatively small number
of plaice is caught; for some reason or other the plaice is less common in
these parts. In the sea around Funen down to Femern, on the other hand,
some more are caught, presumedly a few million plaice yearly, of more or less

20

good quality and size. In the Baltic Sea proper, between Møen and Riigen,
a few millions have been caught of late years, of a peculiarly small, but nume-
rous form, so small that its market-value is but very little. From these
parts eastwards the plaice evidently decreases very much in number; but
Schiemenz has found it east of Gothland at the eastmost of the stations
investigated, and it is found, although sparsely, as far up as Stockholm,
mostly, I presume, on the deep. The places within the Skaw where I have
caught most plaice in the shortest time, are the seas between Riigen,
Schonen, and Møen. Their numerousness here can be compared only to
that of the young plaice (the II and IIl-group) at Thyborøn in the western
part of the Limfjord or at Horns Rev near Esbjerg. At Møen, on the
other hand, we catch, as I have said, almost exclusively grown-up fish. I
shall not here enter into the particulars as to the age, growth, and "races”
of the plaice; they will be given, most likely, in a later publication by one
of my co-workers. One thing only I shall mention: that a numerous and
widely distributed stock of grown-up fish is living east of Gedser (cmp.
table I, column IM), and this though the 0O-group is so rare in these very
seas, that, in spite of all our searching, only c. 50 specimens that may he
assigned to this group, were taken through many years together, against
thousands in our other seas. The following group (I) is also scarce (cmp.
table I, column IM), though perhaps not equally scarce every year (See
«Report of the Biol. Station, IV”, table VII, column 10).

We can imagine this large stock in the Baltic Sea to be renewed in
3 ways only: either 1) exceedingly slowly, by a very slight, annual pro-
pagation, or 2) by a large propagation in certain years, in which the
hydrographic conditions then must be very different from the usual, and
the fry occur in large multitudes, or 3) by immigration. In the first
case the plaice must be very old in the Baltic Sea, of which their otoliths
perhaps might give us information. The researches have as yet never indi-
cated anythiug about a numerous fry in certain years, and this possibility
is most probably excluded, already from a hydrographical point of view.
The only hypothesis remaining is then that of immigration, which Schiemenz
as well as Flwrenbaum and Strodtmann seem inclined also to adopt. It must
then especially be the I-group that immigrated from the Belt-Sea to the
western part of the Baltic. The bodily differences between the plaice in
these seas may very well agree with such a hypothesis. But this immigra-
tion must be elucidated by renewed investigations into the occurrence of
the fry, particularly in the southern part of the Great Belt and along the
German shores of the western part of the Baltic Sea; for in this I fully
agree with Ehrenbaum that the fry must come either from the Belt-Sea or

from the western part of the Baltic, scarcely from the Cattegat properly so
called.

21

på

Some General Remarks on the Distribution of Various Species
of Fish, as Fry and as Grown-up Fish.

That the eel passes certain periods of its life in fresh water, or in shel-
tered seas in salt water, without breeding there, for instance, in the whole
of the Baltic Sea, and therefore must undertake long migrations to go
through the remaining part of its life; that it has, in short, a quite differ-
ent geographical distribution in the different periods of its life, is now
granted, I think, by most people. That something like this holds good
also of many other fishes, has long been known; the salmon breeds in
fresh water, and lives at other times in the sea far from its native place.
These migrations have been termed breeding-migrations, and they have been
compared to those of the migratory birds which we all know. By little
and little the fact of these migrations has become generally accepted. But
we have had great difficulty in reconciling ourseives to the thought that a
fish like the plaice should not go through its whole development everywhere,
where the grown-up plaice are found. And yet we know that the /lounder
often lives in fresh water and gets ripe eggs, although it cannot breed there
so that any fry will come out of the eggs. Now, it is no doubt the rule that
the flounder tries to emigrate to the sea in order to shed; but it is often
prevented from so doing by natural hindrances, artificial dams, or such like,
which the small fry from the sea may be able to penetrate perhaps, but
which are impassable to the grown-up fish. We have here then, close at
hand, an example which reminds us of the plaice in the Baltic Sea. And
how can we expect, after all, that animals requiring such different conditions
of life, as the young plaice on warm sunshiny shores and the grown-up fish
which prefer darkness and cold water on the deep, should have the same
geographical distribution? Is it strange that the fry stops somewhat earlier
on the long and winding way from the Cattegat into the Baltic Sea, than
the grown-up fish? Evidently, however, it is not this either which has
appeared so inapprehensible to many people; rather the fact that the plaice
of the Baltic Sea does not emigrate every year to shed its spawn at more
Javourable places, i. e. places where the eggs can be developed into fry.
Such an inexpediencv seems to many inapprehensible. To be sure, if all
plaice were as unfortunately situated, it would, evidently, be inapprehensible,
if not the eggs, after all, were carried away by the current to more fa-
vourable places, but of this last, however, we know as yet nothing positive. I
believe this way of thinking is a remnant of old learning which was good
philosophy perhaps in its own time; but if we want to understand the
natural conditions as they really are, we had better guard against such
preconceived opinions. Botanists, for instance, know several examples of a
huge wasting of propagative products in nature. Several Phanerogams
are distributed in such a way that through large regions one sex is found
only, the other not; the plants are then reduced to vegetative reproduction,

22

and their flowers are of no use for the propagation. Why must then al
egøs of plaice be shed under favourable conditions? After all, we have al-
ways thought that only a very small number of them, on the whole, become
grown-up fish, even under the most favourable circumstances. To my think-
ing, there is nothing to prevent us from accepting the facts we obtain
by our investigations in nature, even though they go greatly against
what we usually call "expediency”. If the eggs of the plaice cannot be
developed in one sea, then the stock will die out, by little and little, if
not an immigration takes place from somewhere else. If it does not take
place the stock is lost; this, in my opinion, is all the expediency that is
found in nature.

It is not only in the Baltic Sea, however, that the fry of the plaice
belonging to the first bottom-stages has another geographical distribution
than the grown-up fish. I dare say, this is the case in nearly all places
where the plaice lives, for instance in the North-Sea. Here the fry is
found only on a quite narrow strip along the shore, on low water, while
the central parts of the North-Sea are peopled by the older fish only.
Consequently, the plaice cannot live its whole life out here either, and only
the eggs and young fish which come near the shore at the right time can
be developed. We do not know how great a part of the whole number
of eggs and pelagic young fish is condemned to death from the beginning,
because they have got into unfavourable currents which do not carry them
landwards; but we have no right to doubt that many are destroyed before
they are developed, already on account of the hydrographical conditions.
If this is the state of things in the particular home of the plaice, the
North-Sea, why should it not be highly probable that still greater diffi-
culties arise, which may prevent the development of the eggs, where the fish
is near the limits of its distribution, for instance in the Baltic Sea, where,
moreover, the conditions as to salinity make matters very complicated indeed.
There must be something which attaches the plaice to the area within
which they are actually distributed, or rather, there must be something
which prevents the plaice from passing the limits of this area; otherwise
such limits would not exist. Nothing seems to me more probable then, than
that it is the grown-up fish, especially, which can best try to pass these
limits and which actually also do so, hut that the tender fry is stopped
by the difficulties, for instance, the differences in the physical conditions.
I do not see, therefore, that there is anything: to prevent us from supposing,
that the full-grown and half-grown plaice very well can live in the Baltic
Sea, and that the eggs can be shed there, but that the latter cannot go
through their whole development everywhere, where they are shed, when
the results of the investigations, in point of fact, lead to this supposition.
To speak of "die innere Unwahbrscheinlichkeit von dieser Annahme” seems
to me to be quite groundless.

That the fry and the grown-up fish of many species have not always

23

the same geographical distribution seems to become noticed and admitted with
respect to more and more species; I shall only mention that Ehrenbaum in
his last beautiful work on "Fische mit festsitzenden Eiern. Wissenschaftl.
Meeresunters. VI, 1904”, says that the sea-wolf (Anarrhichas) certainly is
found at Heligoland, but whether it "tiberhaupt in der Deutschen Bucht
laicht, darf bezweifelt werden”.

What ought to be the Particular Object of Future International
Investigations?

To examine closely whence the stock of plaice within the Skaw more
particularly gets its increase of young fish, we must study 1) where the
spawning fish are to be met with in multitudes; 2) where their eggs are to
be found in the greatest numbers; 3) where the pelagic larvæ, and 4) where
and when the young fish belonging to the bottom-stages appear on the
shores. I shall not discuss here more closely how this can best be done;
I only wish to say a few words as to the investigation of the bottom-stage.

From table II, page 10, it is seen that quite small young fish are
found at Fænø, station 4; at Nyborg in the Great Belt, station 7; and
partly at Frederikshavn, station 1. They have been taken as small as
10 mm. When we find them so small, we can be pretty sure that they
come from pelagic fry which has lived through its last stages in the neigh-
bouring seas.. But often the fry is not found till later in summer or in au-
tumn, and then it is considerably larger (table II, page 10); in September a
few specimens reach 10 ctm. The current along the shore can now very well
have carried the fry far away from the places where it lived as pelagic fry.
When we have seen the fry penetrate into the Limfjord, from west to east,
or when we have seen what the strong currents in the Belts can carry
along of pipe-fish, gobies, eels, remmants of plants, small stones, etc., we
will understand to value this momentum. The younger we find the 0-group,
the more certain, therefore, we may be, that we are near the places where the
pelagic young fish have lived. At any rate we must take care to keep the
O-group apart from the 1-group, and we do this in the safest way by
measuring the fry. How much help we may get here by examining the
otoliths, I do not know; Apstein's results, loc. cit., do not seem to me to be
very probable, and at any rate they must be supported by measurements
if we shall be able to say anything positive. I shall only point out the
fact that the quite tender fry has not been found in the Baltic Sea properly
so called and at Bornholm; as a rule the young fish found here are more than
3 ctm. I should very much wish to know if they are to be found here in the
first stages, immediately after their transformation. Therefore we must carry
out our investigations in May or June with a shrimp-net of a fabric which
is so closely woven that the holes just permit the necessary sand to pass

24

fhrough; for plaice 10 mm long are very slender, and can go through any
net knit with a needle like a common fishing-net.

I have here mentioned which purely biological conditions it would be
of interest to have investigated with respect to the fry and eggs of the
plaice. But it is another question whether we have not here entered a field
of research which, by a very intimate co-operation of biologists and hydro-
graphers, might give us a greater and deeper understanding of these mat-
ters. By a minute study of the specific gravity of the eggs under different
pressures and different temperatures, together with a close study of the
movement of the masses of water, particularly with a view to the occur-
rence of the eggs, we must he able to get more information; and so I
leave this matter to both lrydrographers and biologists for further consideration.

TE
On the Young Stages of the genus Zeugopterus.

By CNG: Joh Petersen:

(With one Plate.)

Preface.

Though the genus Zeugopterus is of little consequence in practical
fishery, and only one species, the megrim (Z. megastoma), has any market-
value, it is not without use to know its fry; if for no other reason, in order
not to mistake it for that of other common flatfishes, and thus draw wrong
conclusions as to the occurrence of the latter. The determination of the
fry of these fishes has already caused much difficulty. Through the kindness
of Professor R. Collett, of Christiania, and Dr. E. W. L. Holt, of Dublin,
who have sent me material for which I beg to express my best thanks, it has
been possible for me to remove some of these difficulties, by studying this
material in connection with what has been gathered by the Danish Biological
Station and the Thor. I have thought it proper, therefore, to publish these
investigations, though I do not yet know the young of the southmost
species, Z. unimaculatus, but only of the four other species: the three which
are found in Denmark, Z. norvegicus, Z. punctatus, and Z. megastoma, and
the fourth, Z. bosciz which, besides elsewhere, lives also near England.

In 1893 E. W. L. Holt in "Scient. Trans. Royal Dublin Society”, vol.
5, ser. 2, table II, gave pictures of a series of sinistral flatfish, from c.
6—c. 10 mm in length, without any spines on the head, and with a peculiar
development of the caudal fin (two are reproduced on my table I, fig. 6—7).
In the same work, table 12, he gives pictures of 2 other young flatfish,
evidently also belonging to a sinistral flatfish with a similar peculiar develop-
ment of the caudal fin, but further characterised by a pair of large
"otocystic” spines on either side of the head and by a peculiar, striped
pigmentation on the fins and the interspinous bones (see my table I, fig.
1—3). These two types of young ones, the smooth type and the spiny

4

26
type, as I shall here call them, have afterwards always been easy to recog-
nise; but to decide to which species one belongs, and to which the other,
within the genus Zeugopterus, has hitherto caused great difficulties.

The genus Zeugopterus, in my opinion, includes the 5 species: unt-
maculatus, punctatus, norvegicus, megastoma, and boscn. In all these five the
isthmus between the gill-cavities is perforated. Holt himself was in doubt
to which of the two firstnamed species the smooth ones belonged; but he
thought that the whole form of their hody necessarily referred them to one
of these two. With some doubt he then referred them to Z. umimaculatus,
because his oldest specimen had more than 80 dorsal rays and more than
60 anal rays, and this number agreed best with the information he had
found in literature with respect to Z. unimaculatus. As for the spiny young
ones, then he hesitated between R/rombus lævis and Zeugopterus norvegicus.
The number of fin-rays, c. 80 dorsal rays and c. 60 anal rays might very
well refer them to the latter. The young ones of Rhombus lævis have been
described afterwards by others, also by myself in "Report IV”; to compare
these spiny young fish with them is quite out of the question.

IntFJÆMEB TAS (NES) roet SOS FOD EP 202 POSTER Cu:
ningham describes some spiny young sinistral flatfish, from Plymouth,
which. very nearly agree with those described by Holt. They have
as many as 90 dorsal rays and 69 anal rays, and in his opinion,
therefore, their parents cannot be Z. morvegicus. He refers them to 2.
punctatus, which has a larger number of finrays. Of the smooth young
flatfish he gives no particulars.

IM Intosh has on various occasions described and mentioned young flat-
fishes, both of the smooth and of the spiny type. In his last work, "British
Marine Food-Fishes”, 1897, he comes to the result that the smooth forms
belong to Z. punctatus, the spiny ones to Z morvegicus. One of his argu-
ments is that Z. umimaculatus has not been found on the eastern shores of
Scotland; another, and a more essential one perhaps, is, that he has found
that the dorsal fin of the smooth type may number as many as 89 rays
and the anal fin as many as 64 ("10. Ann. Report F. B. for Scotland”,
1891, p. 277). In this respect, consequently, he meets the same difficulties
by referring the thorny type, with 90 and 69 rays, to Z. nmorvegicus, as by
referring the smooth one to the same. He is freer, therefore, in his choice
between Z. norvegicus and Z. punctatus than Holt is, and therefore refers
the smooth young ones to the latter, which, in his opinion, they resemble
most in the form of the body, and the spiny ones to Z. norvegicus
which is more like these. Holt, at first, also thought this to be the correct
determination of the spiny young ones. Z. unimaculatus is considered by
M Intosh to be excluded, because, as above mentioned, it has not been
found on the eastern shores of Scotland.

In "J. M. B. A.” (N. S:), vol V, 1897—99, p. 128—135, however, Holt
again discusses this question, and is of opinion that Cwnningham has proved

D9
<Q

that the spiny larvæ belong to Z. punctatus, probably because they have a
large number of rays, and he is not convinced by M'Intosh's arguments.
Holt, consequently, gives up his original opinion, that the spiny larva
should be the young of Z. norvegicus, and refers it to Z. punctatus on the
strength of Cunningham's investigations.. He does not venture, however,
to speak with any greater decision about this matter.

Ås will be seen from the above, the number of fin-rays has been of
great importance in the whole argumentation as to the determination of
these larvæ"). In itself it is a dangerous thing to rely too much upon the
number of fin-rays; firstly, because only a very small number of specimens
of these species has been examined, and, secondly, because the number of
rays in these fishes varies not a litile.

Lalljeborg states for Z. punctatus: d. 87—101; a. 830—69; vertebræ 36—37,
Z. megastoma:…… d.91—85; a. 75—61; Sy Ælle
ZL. norvegicus: d. 84—79; a.67—58; »… 34—352),

LL... unimaculatus: d. 30—70; a.68—61.

It will be seen that there is here a great variation within the species,
and this variation, no doubt, will be still greater when a larger number of
specimens are examined, particularly if they come from different localities.
The number of vertebræ does not seem to promise much either. It is
necessary at any rate that a larger number of specimens are examined
before anything can be decided. In a Z. punetatus I have counted 9 —+ 26,
and in a Z. norvegicus 9 + 25 vertebræ.

Although the number of finrays, as a character, must thus he used
with judgment by the determination of the grown-up Zeugopterus, this is
so much the more necessary where the young fish are concerned, which
have not yet, perhaps, got all their fin-rays, and about which, at any rate,
we do not know for certain if they have. I shall therefore, for a moment,
leave this matter out of consideration.

In the seas within the Skaw there live only two species of the genus
Zeugopterus, viz. Z. punctatus and Z. norvegicus. Of Z. megastoma only one
specimen has been taken in the Skager-Rack, in 1868 (according to Malm).
It must certainly be exceedingly rare there, and I doubt that it occurs
there normally?). Z. unimaculatus has never been seen in Denmark or
Scandinavia.

When, nevertheless, we find in the Cattegat the above mentioned two

”) By the term /arva I indicate all the young stages which have not yet got the
form of the grown-up fish; consequently, as a rule till the persistent pectoral rays appear
and the eyes have got the same form as in the grown-up fish. All pelagic stages there-
fore are larval stages.

”) According to mv own investigation. The other numbers of the vertebræ are
from Smitt's "Skand. Fiskar”.

?) Cmp. Collett: "Meddelelser om Norges Fiske”. Christiania Videnskabsselskabs
Forhandlinger for 1903, No. 9, p. 89.

28
types of sinistral Zeugopterus larvæ, the smooth and the spiny one, it is,
a priori, the most natural thing to suppose that they must belong to the
two species of Zeugopterus which live in our seas, viz. Z. norvegicus and
ZZ. punctatus. For our seas have been so thoroughly investigated with all
kinds of fishing-gear, that I have no hesitation in saying that neither Z.
unimaculatus nor Z. megastoma can have been overlooked within the Skaw,
if they really have their home here. On the other hand, the possibility is
not excluded, of course, that small young ones of these species can be
carried into the Cattegat by currents. I know that this is the case with
many other organisms. But here such a supposition is not very probable;
more particularly because Z. megastoma is a deep-sea form, and Z. umima-
culatus is not known im the seas nearest to Denmark. I suppose therefore
that the two types of Zeugopterus larvæ must be. referred to the two species
that are found in our seas, viz. Z. norvegicus and Z. punctatus. Z. unimaculata
is out of the question, with us as well as in Scotland, only in Danmark
with greater certainty; for the rocky shores of Scotland can more easily hide
it than our sandy beaches.

At this point my investigations have remained for a long time, as I
was unable to prove to which of the two Danish species the smooth larvæ
were to be referred, and to which the spiny ones. By the kindness of
Collett and Holt I have now overcome this difficulty. Among the young
fish of the genus Zeugopterus which Holt sent me from Ireland, was the
only 9,5 mm long specimen of which a picture is given on table I, fig. 5.
It was caught near the bottom, June 11., 1901, and evidently belongs to a
very late larval stage, whose pectoral fins, however, are not yet fully devel-
oped. In its pigmentation it resembles much the 13 mm long specimen of
ZL. punctatus of which I, sometime, gave a picture in "Report IV”, fig. 15;
it was sent to me by Collett, who himself correctly considered it to be a
young Z. punctatus. Holts 9,5 mm long specimen had no spines on its
head, but a rounded protuberance over the ear-region, on which they might
very well have been placed. This specimen of Holt's also appears to belong
to Z. punctatus by the whole form of its body, its lower jaw, the form of
its dorsal and anall fins, its small and short caudal fin, and finally, its num-
ber of rays, viz., d. about 95, a. about 69. But besides that it reminds you,
on the other hand, of such forms as those of which M'Intosh and Master-
mann in "Food-fishes”, pl. XIV, fig. 8, have given us pictures, and of which
Holt has sent me a specimen from Valencia in Ireland, caught Oct. 12., 1897.
By means of Holt's, I am sorry to say greatly damaged specimen, c. 10 mm
long, with c. 98 dorsal and c. 73 anal rays, with distinct pairs of spines
on, and of fig. 8 in "Food-fishes”, I have drawn my fig. 4, table I. This
figure, drawn from M”Intosh's fig. 8, with ec. 87 d. and c. 62 a., and
from Holt's above mentioned specimen, which were, both of them, spiny, is
in the form of its lower jaw and of its tail, im length and pigmentation,
very like my fig. 5; only with such alterations as may easily be explained

29

by the development of the fish, especially the loss of the spines on the
head. From stages like fig. 4 we come easily to the younger spiny ones,
fig. 1—2. The great number of fin-rays which we find in the here mentioned
specimens, removes them, moreover, so decidedly from Z. norvegicus that
there can be no doubt now that the series on table I, fig. 1, 2, 3, 4, 5,
belongs to Z. punctatus, to which the spiny larvæ must consequently be
referred. But I must confess that it is only after I have become acquainted
with these above mentioned cogent reasons, that I refer the spiny larvæ to
this species; originally I thought that they belonged to Z. norvegicus.!)

From the above it follows that the smooth young fish must belong to
LZ.. morvegicus.… The rather high form of the body (cmp. my table I, fig.
6—7), certainly does not remind you much of the grown-up Z. norvegicus,
which is rather slender; but the decidedly low number of rays does, and so
does the form of the lower jaw. The number of rays in the dorsal, in the
specimens I know (c. 7), is but little im excess of 80, though 82 and 85
are known. I am greatly astonished that M'Intosh has seen a smooth
young one with c. 90 rays in the dorsal, but it is possible, of course, that
he is right. Both Holt and R. Collett have sent me several young ones of
the smooth type, by which I have been enabled to see that the trans-
formation from pelagic young fish to the bottom stage takes place when the
fish is about 10 mm in length, as in Z. punctatus.. That I have non-trans-
formed specimens of Z. morvegicus from the Shetland Islands, still pelagic,
ce. 11 mm long, cannot cause any astonishment, when we know the variations
the development of flatfishes is generally subject to under unequal conditions,
and that the transformation may be accompanied by a shortening of the
length of the fish. In fig. 8 I give a picture of a 13 mm long Z. norvegicus
from Norway (Collett), because it is pretty well preserved, and shows accord-
ance with the grown-up fish in the number of fin-rays, as well as in the
form of the body, the way in which the eyes are placed, the form of the
mouth, the pigmentation and the size of the caudal fin. Collett has also
immediately seen to which species it belongs. I believe that the two series
of figures on table I, 1—5 & 6—8, will make it impossible in future to doubt
that Z. punctatus has spiny larvæ with striped pigmentation, and that Z.
norvegicus has smooth ones.

Besides the young ones helonging to the two said series, there are, in
the collections gathered by the Thor, two which perhaps have been taken
near the bottom, but which, to judge by their glassy appearance, are pelagic
young fish with "otocystic” spines and evidently belong to quite another

") The 10 mm long Z. norvegicus which I mentioned in "De danske Farvandes Plank-
ton, I”, must therefore be referred to Z. punctatus (Kgl. danske Vidensk. Selskabs Skrifter,
6. R., naturv. og math. Afdeling, XII, 3, 1903, p. 260 & 250). — When the biologv of
these fishes ha3 become further elucidated on the basis of the new particulars, information
of the results will be given in the following papers.

30

species of Zeugopterus. They were caught in young-fish trawl (amodytes-
seine trawl) at the Shetland Islands, Septbr. 11., 1903, in water 64 fathoms
deep. In spite of the early stage of their development they are 13 & 14 mm
long. There is a picture of the largest on table I (fig. 9). They are conse-
quently much longer than the nearly quite transformed Z. punetatus, which
is the basis of figure 4. This alone prevents us from referring them to
ZZ... punctatus, but they are also otherwise very different from the somewhat
corresponding stage, fig. 2, for instance with regard to the pigmentation.
Their pigmentation is more like that of Z. norvegicus, but their spines show
that they have nothing to do with this. I suppose that they belong to the
species Z. megastoma, which is common in these parts. I do not possess,
however, all the transitional stages of this species, but I have several, some-
what older specimens, from a length of 27—32 mm, taken by the T'hor, at
the bottom, near the Vestmanna Islands at Iceland, with young-fish trawl,
on a depth of 120—400 meters, in the summer of 1903. One of these,
c. 29 mm long, table I, fig. 10, has evidently lately given up its pelagic
life, for it has still large larval pectoral fins. It has still, however, distinct
pairs of spines in the ear-region, of the the type which we find on Z. punc-
tatus; on the older specimens, on the other hand, these spines are dis-
appearing. That these larvæ, belonging to the bottom-stages, are larvæ of
ZZ. megastoma, is proved by the number of their fin-rays, c. 90—96 dorsal
and c. 72—74 anal rays, besides by their quite external great resemblance,
in other respects, to this species, which was found in large numbers, as a
grown-up fish, by the Thor, among other places also in the same regions.
Moreover, no other Zeugopterus is known here on somewhat deeper water.
Z.. morvegicus, on the other hand, must be found near Iceland, in places
where the water is rather low, because its little smooth young ones, accord-
ing to the above, have been shown to live there. The grown-up fish,
however, have not yet been found, because the place, in spite of all, has
not been thoroughly investigated.

(In the Faroe-Islands I have found a somewhat smaller number of rays
in Z. megastoma, than I found near Iceland, viz., 86—91 dorsal and 66—72
anal rays; but only 5 specimens from this place have been examined. The
numbers will probably prove to vary still more, but it is quite possible that
they, as a rule, are larger near Iceland; this is the case, at any rate, with
Drepanopsetta. In "Ann. Mag. Nat. Hist.”, Decbr. 1899, Gvrinther informs us
that Zeugopterus boscii has 80—81 rays in the dorsal and 63—65 in the
anal, but I think very few specimens have been examined.)

At first I rather doubted that the large, spiny young ones (table I,
fig. 10) belonged to Z. megastoma; for Holt has (l. c. plate XV, fig. 116,
117) two pictures of young specimens of Zeugopterus, 19 & 30 mm long,
which according to his statement have no spines, and these specimens he
refers to Z. megastoma, stating that he had "a complete series” from 19—56 mm.
Now the matter is that his longest specimens (see his fig. 118) very much

resemble Z. megastoma, but it is scarcely probable that this species, already
when it is 19 mm long, should lose its spines near Ireland, when it keeps
them in the neighbourhood of Iceland till it is as long as 27 mm. I take
it for granted, however, that such a skilful investigator as Holt cannot have
overlooked the spines, if they had been there; and it struck me, therefore,
that at least his small specimens without spines do not belong to Z. mega-
stoma at all, but to another species. When this doubt had once risen
in my mind I saw that Holt himself (1. c. page 74) is astonished that
the small young ones resemble "Rhombus bose (Risso)" much more than
ZZ. megastoma; but he supposed that this would change later on. No, this
supposition is scarcely correct; for this little, 19 mm long young one,
table I, fig. 11, is fully developed with persistent pectoral rays and large
eyes, as the grown-up fish. It will hardly change its form. But it agrees
in form very closely with "Rhombus bose (Risso)”, as Holt himself says,
and is much higher over the pectoral fins than Z. megastoma. In order to
obtain better information of the Irish "Rhombus boscir” I asked Holt to send
me a grown-up specimen, and he was kind enough to do so. I had thus
an opportunity to see that this small species (c. 20 ctm. long) in the form of
its body and size of its eyes agrees very closely with my fig. 11, which I
have copied from Holt, and that it was a true Zeugopterus, not a Rhombus,
for it had a perforated isthmus like the other species of Zeugopterus. Because
it is a smaller specimen, probably, it loses its spines at a shorter length
than Z. megastoma, and this, I think, explains why Holt's figures 116 and,
perhaps, 117 have no spines. In "Ann. Mag. Nat. Hist.”, December 1889,
page 418, Gøiinther has given the correct information that the large eyes are
characteristic of Z. bosen in contradistinction to Z. megastoma; but I shall
here caution against a comparison between my figures 11 & 10, as the latter
belongs to a larval stage (the pectoral fins) while figure 11, on the other
hand, is fully transformed. i do not possess any Z. megastoma belonging to
a stage corresponding to figure 11. Loc. cit. Gyinther says that both the
said species have vomer-teeth, and therefore, properly, ought to be removed
from the genus Arnoglossus, to which he hås provisionally referred them.
This is quite correct, of course. They are, both of them, true species of
Zeugopterus, as we now know.

According to the above it must be considered the rule then, that the
larvæ of the genus Zeugopterus, at a certain stage of their lives, have ”"oto-
cystic” spines, i. e. a pair of spines on either side of the head, in the ear-
region. We know only one exception from this, Z. norvegicus, which as a
young fish has no such spines at all. This agrees very well with the fact
that this species, as H. M. Kyle has verbally informed me, from osteologic
and other reasons, must be imagined to be the one which is farthest removed
from the other species of the genus Zeugopterus.

From
rs 124
JL ESE
» 4.
i mb
1.67
BME
28:
» 9.

10.
Sa lg

32

Explanation of the Table. — Table I.

Zeugopterus punctatus.. From Holt (Trans. R. Dub. S. (N. S.), vol. V. Fig. 94.
R, lævis, or R. norvegicus?”). 7 mm long.

> > > ET El e OD)E IO Em me 80 ae 66"

> > > > (1. ce. Fig. 97). Shows the pair of spines in
the ear-region, the "otocystic” spines.

> > Partly from a specimen sent me by Holt, c. 10 mm lang;

d. c. 98, a. c. 73; partly from M'Intosh (Brit. Mar.
Food-Fishes, plate XIV, fig. 8).
» >» Sent by Holt. 9,, mm long; d. c. 95, a. c. 69.

Zeugopterus norvegicus. From Holt: 1. c. fig. 89. 5,,,mm long. "Species XIII”,

» > » 5 10 fe 95 ROS Em long Species KILE,
D. more than 80, a. more than 60.
> > Sent by Collett. 13 mm long, d. c. 84, a. c. 71.
Zeugopterus megastoma. 14 mm long. The Shetland Islands. Septbr. 11., 1903.
> » 29 mm long, d. more than 87; a. more than 72.
Zeugopterus boscii? From Holt: 1. c. fig. 116. 19 mm long.

The figures 5, 8, 9, & 10 are original and drawn by means of a prism.

BIOL. STATION XII

(=

erne

re en
san

VESTERGAARD DEL,

EBA

P. PETERSENS BOGTRYKKERI. KBHVN,

INDB

Can we enter into Competition with the Foreign
Steam-trawlers in our Seas outside the Danish
Territorial Limit?

By C. G. Joh. Petersen.

It is a great advantage to the fisheries in Denmark proper that the
fishermen need but go a very short distance from our principal market,
Copenhagen, to reach the fishing-places. This makes it possible to carry
the fish to the market not only in fresh (unsalted) condition, without ice,
but often living. The goods are therefore first class, and can fetch very
high prices. I believe there are few places in the world where the fishing
is carried on so skilfully and gives such a large income, within such a small
district as our fjords, belts, and shores within the Skaw. But, on the
other hand, it is only of the fisheries on our shores, in /ow water, that I
can speak in this way. In the more open seas, the North-Sea, the
Skager-Rack, nay even in the deep eastern part of the Cattegat, we are
behind our neighbours in turning the stock of fish to our profit. The only
fishery of any greater importance which we carry on in these seas is the
plaice-fishery, which, as it is well known, is based on the catching of living
plaice at rather high prices, and is carried on with seines from welled smacks
on depths which, as a rule, are less than c. 30 fathoms. Nearly all other
species of fish from the deeper parts of these more open seas, haddocks, cod,
pole dabs, etc., we leave to Sweden, Norway, England, Germany, etc.,
whose fishermen here, on depths down to c. 150 fathoms, but in the imme-
diate vicinity of our shores, catch annually for millions of Kroner of fish,
which they sell in all other countries than in Denmark. What we catch
along the western shore of Jutland — when we except the plaice-fishery —
is little compared to the fishery carried on here hy foreigners. The reason
of this is, partly, that we have only one harbour on the western shore of
Jutland; but this is not the principal reason.

Both the general public and members of the Rigsdag have so often
declared that Denmark, after all, must have a better chance of carrying on

5

LÆ 34

the fishery profitably in our neigbouring seas than, more especially, England
and Germany. For the foreigners must sail the long and expensive way
with their steam-trawlers, both from and to their homes, in order to fish
on our fishing-grounds; and if this can be profitable to them, it must be
still more profitable to us to carry on these fisheries. Yes, probably it is
so; but it must be remembered that the price of coal is somewhat lower
in England than in Denmark, and that there is both in Germany and in
England a much greater, already well-established, market for trawl-caught fish
than in Denmark. When I have formerly regarded this matter as quite
hopeless in Denmark, the reason is, more particularly, that a certain circum-
stance connected with it has not been clear to me till quite lately. I have
not thought it possible that the fish the trawlers take, haddocks, cod, deep-sea
flatfishes, etc., could fetch acceptable prices in Copenhagen; for trawl-caught
fisb, as everybody knows, is not living. The steam-trawlers generally catch
such large masses at a time in the trawl, that the fish is squeezed to death
in the trawl while being hauled in. Such fish are therefore not first-class
goods like our usual, living fish. The trawled fish is iced in the warmer
season, after it is cleaned; in the colder season, which on the whole will
be the best if not the only time for trawling, this is not necessary. The
trawl-caught fish, which is the principal commodity on the European inland
market, is as yet but little known here. But these last winters a couple of
small trawlers (one with steam and another with sails and auxiliary engine)
have carried considerable quantities of all kinds of fish, from soles, turbots,
and plaice to cod, haddocks, lemon dabs, etc., to the free-port of Copenhagen,
where they have had a ready sale, though the fish are not so good as living
fish, only because the price is lower. There is, consequently, an indication here,
that Copenhagen will eat second-class fish, if obtainable at proportionate prices.
This was the circumstance of which I wanted information.

It is scarcely necessary to state that fish is nearly always very dear in
Copenhagen, i. e. first-class plaice, cod, and other living fish. 50 Øre per
pound of plaice and 25 Øre per pound of cod are not uncommon prices,
and it seems zhat second-class fish is always rare in thus city, at any rate
at low prices.

In order to be able, in rough outlines, to make a comparison with
Germany, where the market is based on trawl-caught fish, I shall mention the
average prices for 1903 in Geestemtinde harbour, where more than 100 steam-
trawlers land their fish, chiefly caught in the North-Sea, the Skager-Rack,
and the Cattegat.

According to the official statistics of Geestemiinde for 1903, the average
price for cod was c. 11 Øre per pound, for plaice c. 13 Øre per pound, and
for haddock c. 8 Øre per pound. These are auction-prices, consequently whole-
sale prices, and I want expressly to say that we can never expect to obtain, even
approximately, such good fish as those which are sold at present in Copenhagen,
at such low prices. Most likely, it will never happen; for there is so great a

35

difference in quality between these commodities that they, in my opinion,
will never compete in our Danish market. There will always, I dare say,
be people to buy the good, living fish; but these fish are and must be looked
upon almost as a luxury. I only mention how matters are standing in
Germany, to show that trawling gives inferior, but cheap fish; and it is
my opinion now, that many people in Copenhagen will be willing to buy
these fish, who, as a rule, never before had fish on their table.

It is possible, consequently, provided that the general publie will be inclined
to buy the fish, that it will pay to carry on trawling from Copenhagen, because
we are situated mnearer to the fishing-grounds in the North-Sea, the Skager-
Rack, and the Cattegat than most nations; and it would be a great advantage,
particularly to the less wealthy part of the population, more especially in Copen-
hagen, if cheap fish, even though of second quality, were carried to the market
by the trawlers.

I could imagine now that the introduction of trawling into Denmark
(whether carried on by means of larger steam-trawlers or by a number of
our fishing-smacks, changed in such a way that they could use small trawls
or otter-seines) would be objected to as an injurious way of fishing: 1)
because it destroys the stock of fish; 2) because it will set up a competition
with our present fishermen; and, finally, 3) because it will give the manage-
ment of the fisheries into the hands of capitalists and so produce a
number of hired people, who would otherwise be independent owners of
their small vessels.

Note. We have in Denmark for many years heard of trawls and trawling,
but only few people here know what a trawl is. We have heard our fishermen
complain that foreigners are trawling near our shores, although on international
sea-territory, and thereby preventing their usual fishery with nets and seines.
These complaints are nearly all that the general public knows about the trawl.
The ideas of injuriousness in general, and of trawling, have thereby become so
mixed up in Denmark that it will be no easy task to place them in the rela-
tion to one another which sober truth demands.

It appears, however, that the legislative power labours under so great diffi-
culties in laying down a fixed rule for what a trawl is, and what a seine is,
that different results have often come out of it. Both of them are more or less
hag-formed nets which, spread out in different ways, are dragged along the bottom.
The worst objection we, from a technical point of view, can raise against the
large trawls, used by steamers and large sailing-vessels, is, that it is often
impossible for them to bring the catch living on deck and here separate the
fish which are fit for use from the useless ones, while they are still alive. In
other words, they are most frequently prevented from placing the fry again in
the sea in a live state. This can be done with most of our seines. But these
are generally employed on lower water, where it is always easier to get the
fish up alive. The trawls, on the other hand, are usually employed on deeper
water, where it will generally be impossible, with any kind of fishing-gear, to
bring the fish living on deck, because the fish suffer too much, already by being
brought to the surface from the deeper water. What is really characteristic of
trawling is that it is carried on with large, powerful boats, day and night, in

36

good or bad weather, on low, but particularly on deep water, and, finally, that
the boats catch large numbers of fish, generally so large numbers that the
weight of the fish themselves, during each hauling-in, is enough to kill most of
them, so that they cannot be delivered to the market in living state.

As to the stock of fish, then, it is seen by the statistics of our fisheries,
that Danish fishermen catch for c. 2 million Kroner of plaice annually in
those of our seas where foreigners are now trawling and where, consequently,
also our own trawling should be carried on, namely the North-Seu,
Skager-Rack, and the deeper parts of the Cattegat; in all three seas on inter-
national territory where the Jishermen of all nations, consequently also the
Danish, are permitted to fish. But of all other fish together (including cod,
haddocks, lobsters, oysters, herrings, mackerel, etc.) they also catch only for
about 2 million Kroner. The plaice are, consequently, absolutely predomi-
nant, and the reason is that we chaefly fish for plaice, and carry on the fishery
on low water.

If, on the other hand, we look over the accounts of the somewhat more
than 100 steam-trawlers which land their catch at Geestemtinde, then we
see that the plaice give only 280,000 Marks of the c. 5 millions, which
came in at the public sale in 1903, but the other species of fish altogether
Cc. 18 times as much. Among these other species of fish we find that '"small
haddocks of the fourth sort and whitings” give the largest amount given
by a single class of fish, viz. between 6 and 700,000 Marks, and they sell
at 5!/, Pf. per pound. Haddocks give, all in all, more than 2 million Marks,
cod c. 1 million, pole dabs 400,000 Marks, green cod 150,000 Marks, soles
190,000 Marks, turbots 140,000 Marks, and the remaining amount is dis-
tributed over a number of other fish of less importance, which are seldom,
if ever, sent to the market in Copenhagen.

It will be seen, then, that the trawlers do not particularly pursue
the plaice in these seas, as our plaice-seine fishermen do. We may
rather say that these two ways of fishing supplement each other. One
is based on plaice on low water; the other on roundfish on deeper water.
This is why our plaice-seine fishery has been able to thrive very well, on
the whole, beside the foreign trawlers in our neighbouring seas; and I do
not think our principal fishery will get into danger, if we add a few Danish
trawlers to the international trawling-fleet. They will not catch such large
numbers of plaice that it will be of any consequence, compared to what we
ourselves catch of this fish im other ways; and it is particularly this fish
that needs protection. I believe, therefore, that Denmark can take part
in the trawling on international sea-territory, 1. e. outside our fjords and
belts and the lower parts of the Cattegat, without any fear of destroying
the stock of fish (stock of plaice). Whether the deep-sea stock of fish, as a
whole, can bear a great addition to the existing fleet of trawlers is another
question, though presumedly one which belongs to the future; and its
solution will scarcely be affected by the presence of a few Danish trawlers.

37

It must not, therefore, prevent us from taking part in the international
progress in fishery. It does not appear that the foreign nations pay regard
to such matters; and to stop their development is at any rate beyond
our power.

Indeed, we must hope for an international protection of the stock of
fish, where protection is needed; and, no doubt, a prohibition against
trawling at certain places would be desirable, perhaps in certain months of
the year. But a general prohibition against trawling in all the deep parts
of our seas will presumedly be quite out of the question; for by trawling
only, I think, it will be possible to make an adequate profit out of the large
deep-sea stock of haddock in winter.

Ås the trawling in the said seas is not based particularly on plaice, it
is my opinion that also the second objection, that it sets up a competition
with our own fisheries by bringing cheap fish on the market, will be of no
greater weight, except perhaps with respect to the cod-fishery. But cod and
haddock caught on hook is a far better commodity than the trawl-caught
fish, also abroad, and cod taken in traps is living. I do not see how the
trawl-caught fish, which is to be bought hy a quite different class of people,
will be able to do any greater harm. But I do see that we profit too little
by the roundfish (cod, haddocks, gurnards, etc.) and deep-sea flatfish (pole
dabs) which live in the deeper parts of our seas, and whose numerousness,
through a great part of the year, has been proved by the investigations
carried on by "Kommissionen for Havundersøgelser”, through Dr. A. C. Jo-
hansen, on board the steam-trawler Thor. German, English, and Swedish
trawlers take, for the present, by far the greater part. Scores of times I
have seen the German steam-trawlers pass southward through the Great
Belt, bound for Hamburg, loaded with fish taken in the immediate neigh-
bourhood of our shores, but on international sea-territory. Our territory, it
must be remembered, is only 3 miles broad.

Ås to the third objection, that capitalism might possibly acquire an
undesirable influence, I shall say only that trawling is the only fishery that
can be carried on where the foreign trawlers are (the otter-seine I look
upon here as a sort of trawl); everything else will be molested by the
trawling vessels. We must trawl, consequently, if we will not quite give
up the idea of getting some part of the profit. Moreover, it will scarcely
be a large fleet of trawlers we can expect to supply Copenhagen with fish,
and as already mentioned, our fishing-smacks with powerful motors will
possibly be able to partake in this fishery. The latest experiments with
such vessels in Germany seem to prove that a fishing-smack with a motor
of 16—20 H. P. can drag a trawl some 50 feet in width. Finally, one thing
more: if the prices for trawl-caught fish do not remain high enough in Germany,
then the German trawlers can sell their fish in Copenhagen, whenever they
like. No one can forbid them to do so; they are going to Frederikshavn
already, now and then, with their catch; and rather than that should

38

happen, it seems to me, that we must overlook any possible smaller draw-
back to the introduction of trawling. But if we consider it our principal
object, to procure cheap fish for Copenhagen, then we could simply make
an arrangement with German or English trawlers about the delivery of fish
for Copenhagen; we should then run no risk by starting a great undertaking
with Danish capital.

I have now, I think, stated the whole matter, and enlightened it from all
sides, such as it appears to me. When I have not before expressed any
opinion as to the possibility of trawling with large vessels from Denmark
in order to supply the Danish market, the reasons are: the difficulty in
seeing whether there are here buyers for the trawl-caught fish, and the fact that
I did not know that the number of fish was sufficiently large on our
shores through such a great part of the year (at least from October till
May). It must be remembered that the question is here particularly of
roundfish, migratory fish consequently, and pole dabs. When earlier
Danish steam-trawl companies, which have employed Danish vessels, have
not carried the fish to Copenhagen, I must suppose they have had parti-
cular reasons for it; but this need not prevent others who might desire to
try such trawling from a Danish harbour.

One should think that it is in itself a handsome object for private
enterprise, to supply Copenhagen and the rest of Denmark with cheap fish,
as it must be looked upon as a patriotic task to set up a competition with
the foreign nations in our own seas. If my exposition of the matter can
help to call up private initiative, I should be glad. For besides this, my
only intention with the above has been to make it clear how we are stand-
ing in this matter as regards foreign countries, and to free myself from
the responsibility I should feel by being silent about it.

How to enter upon it in the best way, is a question I shall not
discuss here. There are many possibilities; but the object must be: fo
obtain for Copenhagen a constant supply of cheap, trawl-caught fish. "hat the
practical accomplishment of this whole matter will meet many difficulties,
I shall only mention. One of these difficulties will, doubtless, be the
sale of the fish, as it would be necessary, sooner or later, to get a suitable
covered fish-market where the public sale could be held. But with regard
to this I think that the undertaking may reckon on the powerful support
of the municipality of Copenhagen, as this city first and foremost would
benefit by the new enterprise. To prepare the transition from the present
state to something better, the catch might also be sorted at Frederikshavn,
or in the new harbour at the Skaw. Part of it could then be sent by
rail to Hamburg where, for the time being, there is an unlimited market
for trawl-caught fish. It would then be necessary only to sail the few miles
from Frederikshavn to Skager-Rack, where no doubt the principal fishing-
grounds will be situated.

39

It has often heen discussed, in private conversations, whether we ought
m Denmark, as it has been done abroad, to go over to the sale of %illed
instead of /wving fish. This is not what I here propose. We should, decided-
ly, always continue to produce all the good, living fish we can; hut we
ought not, for that reason, to neglect benefiting also by the fish which
cannot be brought to market in living state. Even though they turn out
to be of second quality, we learn from the German statistics that this is
to a high degree compensated for by their number and cheap price.

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