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Report

of

The Danish Biological Station

to

VIII.

1898.

By

C. G. Joh. Petersen,

PhD:

"Ya. --

SJ

Kjøbenhavn.
Centraltrykkeriet.

899:

From

The Danish Biological Station.

NETTT.

h H8S5se

Kjøbenhavn.
Centraltrykkerict.

1899.

tore Fr raps fa

An Otter-Seine

For the Exploration of Deeper Seas.

(With 10 Figures.)

BCS GS Jobs Petersen:

1898.

År a time when so many institutions, in Europe as well as elsewhere,
are busily investigating the seas and their animal life, it will be a good thing
to call the attention to improvements on the fishing-gear employed in this
undertaking. As my experience in these matters have, presumedly, led to such
improvements, I shall here mention them more closely.

It was almost a matter of course that the naturalists by their deep-sea
investigations at first imitated the fishing-apparatus used by the fishermen:
the dredge, for instance, in all its manv forms, is certainly an imitation of the

oyster-dredge, and like the latter calculated only to catch smaller and not very

Fig 1. A double-trawl. (After the Prince of Monaco.)

quick animals; the trawl, on the other hand, was introduced just to catch the
larger and quicker animals. This also is originally an imitation of the fisher-
men's trawl, particularly the beam-trawl, but im two things, nevertheless, the
»scientific« trawl differs from that of the fishermen: it is much smaller, and
it is usually double, i. e. made in such a way that it can fish whether it falls
on one side or on the other (fig. 1). It was the Americans who introduced the

3

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double-trawl, and it was long considered a great improvement on the ordinary
single beam-trawl, which may sometimes fall on the wrong side, and is then
incapable of fishing anything. It is a drawback, however, to the double trawl
that its fishing opening generally can be only half the size (height) of that of
a beam-trawl of the same width, and that its mouth during the dragging in
is more dilated, so that the water will rush
through it and spoil the finer organisms. More-
over, compared to the single beam-trawl, it
is said to be objectionable on hard bottom,
because its »fishing-ropes«, the ropes which
scrape along the hottom, are so tight that they
often take hold suddenly and burst. When we
see, finally, that Z. L. Tanner, North-America's
most experienced explorer of the deep-sea, in
his recent description of the apparatus used
onboard the »Albatros« (Bull. of the United
States Fish Commission, vol. XVI. 1896, p. 357)
says that the investigator always, with few ex-
ceptions, will be able to make the single beam-
trawl (fig. 2) fall to the bottom in the right way,
even on the greatest depths, the double trawl
(the Blake trawl, Agassiz” trawl), presumedly,
will scarcely be used in future, except when, from
various reasons, it is impossible to employ any
other fishing-gear. It must be granted that it

has been of great service to science; many un-

Fig. 2, A single beam-trawl. (After known animals have been caught by it; but it
Tanner,) — The length of the beam is . = z = å n
ungt feet is a fishing-apparatus which differs much from

the traditional one, i. e. from the trawl used
by the fishermen in their daily work. We must remember also that a fishing-
apparatus in such general use as the English beam-trawl represents the expe-
rience acquired by many people through long times and with huge labour;
and we should not without cogent reasons give up a thing which has been
approved by experience. An Englishman would hardly have ventured to do
so, and it is scarcely accidental that it was an American who did; for in Ame-
rica trawling is not known in professional fishery.
In America, however, where scientific deep-sea investigations are carried

on regularly, they have, as we learn from the report (1896), partly returned to

Bum

the single beam-trawl, which is almost similar to that used by the fishermen; but
it is remarkable that, although the American exploring vessel compared to an
English steam-trawler is a very large ship (234 Eng. feet long and more than
1000 tons of deplacement), its trawl is only 11 feet wide (the beam 11 feet),
while the trawl-beams of the English trawls are as long as 40—50 feet. That
the trawl for scientific use must have somewhat smaller meshes, and must be
caleulated to be sunk to greater depths than the fishermen's trawl, cannot
quite explain the disproportion of the size of the trawl to that of the ship, at
any rate not when the depths are not too immense. The soft hottom-material,
certainly, may be gathered in considerable quantities im a trawl with
small meshes, and thus make it heavy; but this difficulty might be overcome.
I cannot quite understand why the large vessels which have carried on scientific
investigations in the seas, at places where they are able to fish, have not used
trawls at. least of the same size as those used hy the fishermen. It must not
be imagined that such trawls would not catch any other animals than the
small trawls. All zoologists would be most anxious, certainly, to see a draught
of fish by large trawl on deep water; and they believe, all of them, that the large
and quick animals, fish as well as cuttle-fish and large crustacea, make their
escape as soon as they leel the proximity of the ordinary, small fishing-apparatus.
We must go on, therefore, in this direction, and have larger fishing-gear; and I
should think that the leader of the next deep-sea expedition would do well in going
onboard a modern North-Sea trawler and study her method of fishing, for in recent
years a change has taken place here in the construction of the gear, which will certainly
be useful also to science. — What all deep-sea expeditions have been afraid of
is, I dare say, the large trawl-beams, which it is no easy matter to manæuvre
in a heavy sea, or in vessels that are not especially built for them; but now
lately, in the course of these 3 or 4 years, the fisherman has just learnt to
do without the beams, and yet he can fish better than before. His trawl has
now an opening of 80—90 feet, while it was formerly 40—50, and at the
same time his gear is cheaper, it is easier to use, and it fishes better than
before. The beam is done away with, and two slanting wooden otter-boards
mounted with iron on the nether part, stretch out the trawl wlule sailing, so that
its opening can be made as large as you want it; and yet the gear will not be
much more difficult to manage above the water. — This is the new so-called
»Patent Beamless Trawling Gear« or »Otter-Trawl«. With respect to this
gear the Danish Fisheries Agent in England says in his report, 1895,
as follows: «This year a great revolution has taken place in the English trawl-
fishing. The beam-trawl has been replaced by a so-called otter-trawl. A Dane,

who has been trained up in the English trawl-fishing, has constructed a trawl
which, instead of being kept open by a heavy beam, is kept open by means
of two iron-mounted wooden boards, which stand erect in the water, fastened
to the vessel by cables of steel-wire, and which, by the speed of the vessel, re-
move from one another and thus keep the net open«. — »The new trawl has
quite replaced the beam-trawl among the steam-trawlers in Grimsby and Hull,
and even in Belgium and Germany it is now being introduced.« As to the
whole historical development of this matter with respect to the professional
fishermen I shall refer to a note by J. Spillmann (illustrated by H. Giebel) in
»Mittheilungen d. deutschen Seefischereivereins 1896« pp. 1591—156. According
to this, a Dane, Captain Nielsen, of the Danish fishing-steamer »Dania«, has

first understood to use the otters in the right way. —

Fig. 5. The English »Otter-Trawl«.

When this trawl has not become general till these latter years, though we

have also before known »otters«”) i. e. boards for the spreading of the net, one
reason among others is that they cannot well be used without steam, and it is
not till quite lately that we have introduced steam-trawlers. This gear is certainly
the »best« our time knows of — the fishing-apparatus which is most terrible to
the fish. A haul with it, of 4—6 hours, as it is usually made, hut out on the
greatest depths, will certainly, with a little good luck, give as many fish as an
ordinary deep-sea expedition generally brings home. Such an otter-trawl (or
»Skovl-Travl«, if you prefer that name) is dragged hy the fishermen, however,

£) English Otter, Norwegian Oter, and Danish Ødder is the same word employed
figuratively of a somewhat older fishing-apparatus used in fresh water. A wooden hoard
of the same construction as those of the trawls is here used to stretch out a line with
hooks from a boat while sailing. This gear has been called otter, because it fishes so
well. A trawl with two otter-boards was then called ottertrawl; but I think the Danish
Skovl-Travl or Skovl-Vaad is a better name, and this has been used also in Denmark for
some plaice-seines with boards, employed by the fishermen in the North Sea. — The
seine described in this paper is a eel otter-dragseine.

9

in two lines, one line for each otter, and is used only on depths up to ec. 100
fathoms; on greater depths it has been necessary to make other arrangements,
to which I shall afterwards return.

In all the years I have been the Director of the Danish Biological Station
we have never had occasion to make deep-sea investigations. The Danish
seas are shallow, and the fishing is generally limited to depths under 10
fathoms; there we can easily manage otherwise. Not till 1897, when the inve-
stigations were to he carried on in the Skager Rack as also, at the request of
the Norwegian government, in the deep Christiania Fjord, I must make arrange-
ments for going deeper — as deep as 2—300 fathoms. My first thought was
then to use our ordinary eel-dragseines for this fishery, in a similar way as that
im which our fishermen use them aft several places, i. e. with a beam which
extends them. and which indeed gives them a great resemblance to the beam-
trawl. (Cmp. Drechsel: Oversigt over vore Saltvandsfiskerier. 1890. Pl. XV. A.)
The eel-dragseines are so common in Denmark; every detail of their construc-
tion is so well known by our eel-seiners; the fishing capacity of the gear is
splendid, nay, quite notorious, each and all characteristics which made me
choose this apparatus instead of trying to make a beam-trawl. For there are
not many here, at any rate none that I know of, who are able to construct a
beam-trawl correctly in all details; moreover, the fishermen of the Biological
Station are not practised in the use of such a gear which, be it remembered,
is forbidden by the Danish law.

Now, I do not mean to say that it would be difficult to us (to my men
and myself) to make a beam-trawl, which everybody who is not an expert in
these matters, whould consider a very good beam-trawl; but it is a most diffi-
cult thing to teach oneself a quite new way of fishing, and it takes such a
long time to do so, particularly if the fishing is to be carried on further than
to the very first stages, that I thought I ought not to commence it without
cogent reasons, more particularly so, as I knew that the time which could
be employed for this purpose onboard a steamship was but very limited.

Nothing would have been easier, of course, than to order a suitable trawl
from England; but this would not by far have cleared the matter. For even
if such a trawl was im perfect order to commence with, and well calculated
for English conditions, it would very soon be changed by use, and if you do
not know by experience what is the matter, but have to make it out for your-
self, you must be prepared to get a troublesome work, which will take you
long time.

There are those who will say perhaps that these things are trifles. If the
2

10

gear can fish, then it is all right, and it is all the same whether it is made in
one way or another. I thought so myself formerly. But 15 years' work has
taught me something else: by studying the use of our various sorts of fishing-
gear, by personally fishing with them, by having in my service and talking
these matters over with some of our most intelligent fishermen, I have learnt
that there can be an immense difference in the fishing capacity of fishing-gear
which, superficially examined, looks alike: one apparatus has little faults in
the construction while another is made as it should be. All of them can fish
something, that is true; but the more difficult fish, eels for instance, are not
to be caught by any seine, even though the meshes are small enough. — I still
remember, though it is more than 12 years ago, the pity with whieh the fishermen
sometimes looked at my first fishing-gear, among other things just a little
double-trawl. They were right, in ås far as such gear should be used only, if
we can use no other, or if we do not care particularly to catch large, quick
animals; but we cannot pretend with such gear to thoroughly investigate the
stock of fish in the sea. If we will make fishing-gear, we must learn the trade,
go through our apprenticeship, just as well as, for instance, a tailor must learn
his trade; tradition and fashion are of great consequence to both crafts. When
I particularly mention the trade of a tailor, it is because I here find so many
similarities. Å seine must have no other folds than those necessary, or
the current that runs through it will be influenced disadvantageously, and
the fish will take the alarm. The whole form of the gear must be correct,
without the slightest obliquity, etc., and we cannot see its form till we try it
on, i. e. till it is placed in the water; not till then, hy floats and weight and
the pressure of the water, it gets is proper form. One seine can »fish«, another
one »cannot fish«, says the fisherman; and the fishermen have a thorough
knowledge of all details which are here of any consequence, rarely written
down, but generally enherited by tradition from generation to generation.

It will now be understood, why I selected a Danish fishing-apparatus,
the drag-seine, for fishery on waters of a somewhat greater depth. As above
mentioned, we tried it first with a beam; this, however, proved to be unprae-
tical. The fishermen can easily use it with a beam on 3—4 fathoms of water,
because they let the beam float in the surface; there will be no danger of its turning
round. But on deeper water, where the fishermen never come with eel-seines, the
beam must under the water, and then the difficulties appear. The beam of 12—14
feet in length was soon abandoned, and two otter-boards from Plymouth, which
I happened to get possession of, were employed to extend the arms of the
seine, It appeared that the eel-seine in this way very well could be used like

11

an ordinary otter-trawl. By certain winds it could be dragged on low water
by a small sailing-vessel of 4—5 tons, and it fished a great number of fish,
among others many eels, which are considered the most difficult fish to catch.

Two otter-trawls, made in this country for these very two boards, proved,
on the other hand, to be failures, whether now this was owing to mistakes
made by the constructors (one of them had been to England and was said to
understand the art very well indeed), or the reason was that we did not under-
stand how to use them. The drag-seine, however, fished well. It was dragged

Fig. 4, Sailing-vessel with otter drag-seine, belonging to the Biological Station.

in two lines, one for either »otter«; but I soon discovered that it was as well
to drag it in a crow-foot, from the vertex of which only one line passed on-
board the boat. (Cmp. fig. 4.) We were now able, by only making this line long
enough, to drag with the seine on any depth, if we had only sufficient power
to drag it.

A problem on which I had been pondering for years — how to employ
an eel-seine from a steamer on water of greater depth — was thus solved, and
we have got a fishing-apparatus which is eminently calculated to catch the
livelier animals on deep water. Moreover the gear has small meshes and is
therefore able also to catch smaller fish. With ordinary, suitable speed it is
extended to about 12—16 feet, and it is thus at least as large as the usual trawls
employed by the greatest vessels for deep-sea investigations; yet it is so easy

12

to manage that I have been able to use it from a steam-launch (32 feet long)
on a depth of 30—50 fathoms; and had not a steam-winch been wanting for
heaving-in the wire-ropes, a powerful steam-launch would be able to manæuvre
it, and use it with profit, on a depth of several hundred fathoms.

With such an apparatus, an eel drag-seine with boards, I have this sum-
mer made many hauls on depths between 1 fathom and 300 fathoms. After
the first difficulties in finding the suitable speed, hoards of suitable size and
weight, crow-foot of suitable length, etc., had been overcome, the gear has
worked excellently. I have, in 1897, employed it from no less than 7 various
steamers of very different sizes, as also from a sailing-vessel, on very soft as
well as on hard, partly stony hottom in the Cattegat, the Skager Rack, and in
several Scandinavian fjords, for instance the Christiania Fjord, and it has never
been quite torn to pieces.

In the following the details of this fishing-gear will be more closely de-
scribed; first, however, I must make a historical observation. —

Besides the beam-trawls which have been used on the various deep-sea
expeditions, the size of which (the length of the beam) was, for instance, on
» Vøringen« 15 feet, on the »Albatross« 11 feet (Tanner beam-trawl), the »Blake«
10 feet, the »Pola« c. 10 feet, etc., the Norwegian north-Atlantic expedition in
»Vøringen« has also made use of a small otter-trawl, and just in the same
way as I employed the eel drag seine, i. e. with a crow foot.) This otter-trawl,
however, was hut very little used in »Vøringen«, not because it could not
catch anything, but because it so often became foul when it was placed in
the water. Twice, however, they succeeded in getting it out clear, and both
times the result was excellent, a great number of fish being caught. The gear
is mentioned only very briefly m the report, and a picture of it is given, but
im such a way that we cannot form any clear conception of its real form. It
is n0 easy task to picture and describe seines and trawls accurately — I grant

that — but we do not get over the difficulties by pretending not to see them,

=) I Scotland they have on various occasions made use of larger beam-trawls in
fisheries for practical-scientific purposes, on a depth of as many as some hundred fathoms.
As far as I remember, the beams were c. 20—50 fathoms long; but on the greater expe-
ditions they have always been much smaller. — The fishing-gear from the French expe-
ditions in the »Travailleur« and the »Talisman«, which have caught an unusually large
number of fish, is mentioned in »Annales hydrographiques«, 2. Ser. T, V, 1883, pp. 24—25
and p. 281, as also loc. cit. 2. Ser. T, IV. 1882, pp. 385—398, particularly p. 389. It seems as if
they have first (in the »Travailleur«) made use of a large trawl with a beam 7 meters
long and then afterwards (in the »Talisman«) changed this for a »Blake-trawl« of 2—3 me-
ters. — The reason for this is not stated.

15

and this, with few exceptions, has been the usual custom. Among these excep-
tions must be mentioned Tanner and the Duke of Monaco, who with his pro-
portionally small vessel, the »Hirondelle«, has done much, and particulary paid
great attention to the apparatus, of which several new ones have been con-
structed, particularly deep-sea weels (traps) and an otter-trawl for pelagic fishery
which m its construction with crow-foot and hoards very much resembles
the one I have used; the net-apparatus, however, is quite different.

We must not lay too much stress, however, on the unsuccessful experi-
ments which » Vøringen« made with otter-trawl or rather, I think, with otter-
seine; for if we have no practice in the use of such a one, and if the vessel,
as the case was with » Vøringen«, is rather large in proportion to the trawl,
the fishery will easily turn out a failure, particularly in unfavourable weather.
Here as everywhere some practice in necessary. The first times we tried to
place an oftter-seine in thé water, we failed nearly every second time; since then
I have personally manæuvred the steamers, and made more than 100 hauls
on all depths, down to 200 fathoms, without a single failure from that reason.
The principal thing is, all the time while you are lowering the gear, to hold the
line so taut that the boards are constantly removing from each other, a thing the
man who veers out the line very quickly learns; at the same time, of course,
the vessel must go on by the propeller. When the length of line you want to
get out, is out, the speed is diminished so much that the seine is allowed to sink
slowly to the bottom. — On these depths, up to 2—300 fathoms, I have found it
superfluous to use an accumulator for the tow-rope, which of course was of steel-
wire; in a high sea it will be necessary, however, if there is anything heavy
in the seine. The wire-rope has during the dredging been fastened round the
trundle-head of the steam-winch, so that we were able, if the seine should take
too firm a hold of the bottem, to veer away and then heave in. The tow-rope
has during the trawling always gone astern, either through a jaw on the stern-
sheets, or, and that is the best, along the side of the ship, over the how,
through a short, strong davit, or the like. (Cmp. fig. 5.) In the latter case the
rope has, during the fishing, on the short vessels, been hung up and made
fast under the buttock, so that it could not get into the propeller. When they
are to heave in, they let go from the buttock, and the vessel swings to the
seine while they heave in — provided that the vessel is not too large in pro-
portion to the seine. For the sake of the manæuvring as also in order to get
a suitable speed, for the sake of the fishing itself consequently, there should
be, evidently, a suitable proportion between the size of the vessel and that of the
seine. The ship should feel that it has something to drag, or the speed will easily

14

be too great and, where you can see no land, difficult to judge of, particularly
when the weather is unfavourable.

To lift the whole seine up over the water, as they do by the usual deep-
sea investigations, by letting the tow-rope go through a block high up in the
rigging, so that the whole apparatus, while it is taken in, is floating in the
air, stretched out, is against all good fishing-practice, and is, moreover, almost

Fig. 3. A small steam-boat with an otter-seine, — The dotted line marks the disadvantageous situation of the
gear, when the crow-foot drags along the bottom. — The depth of the water is somewhat great in the figure
in proportion to the length of the line.

impossible with this long apparatus. The rolling of the vessel will also influence
the gear much more during the hauling up, and an accumulator will then
certainly be quite indispensable; moreover, if the contents of the seine
should be very heavy, the seine may be torn to pieces by being lifted out of
the water in this way. The tow-rope must not be fastened much higher up
than the rail, and the seine must ultimately be hauled in by hand till
the strong bag is so high up that you can pass a strap round it, and bouse

it im, if necessary. First, however, you wash out, by backing or going on with

15

the vessel, as much mud as you think fit. In short, you do just as a trawler
when he takes in his trawl. On a very soft bottom, particularly where
there live many Brissopsis or Fchinocardium, the seine may be filled with
bottom-material. This can be avoided by fastening an old, flexible, and thick
coir-rope (2—3 inches im diameter) to the foot-rope. — I think it superfluous
here to enter into the details of many other things which must be taken into
consideration while trawling: the direction of wind and current, etc. (As to
this cmp. Tanner: Deep-Sea Exploration. Bull. U.S. F.C. Vol. XVI. 1896.
pp. 390—95). -—

The otter-seines I employed consist, as to net-apparatus (cmp. fig. 6), of
two arms, each of them 300—340 meshes long and in their whole length 100

Fig. 6. The otter-seine employed by Petersen.
M. means meshes. Tom. means Danish inches. — Each arm is c. 24 feet long and the bag c. 16 feet.

meshes deep, fastened to the hag (at he mouth of the seine). The bag consists
of a forepart and a hinderpart, and contains a pocket fastened to the hindmost
border of the forepart of the bag. "The forepart of the hag is 36 meshes long
and 400 meshes in circumference, all through. The foremost border adjoins
either arm with 100 meshes; of the remaining 200 meshes (100 above and
100 below) 100 are sewn on to two feet of, respectively, head-rope and foot-
rope, exactly the same for both, and, as shown in the figure, with 6 »hitches«
(12, 16, 22, 22, 16, 12 — 100 meshes on 2 feet of the rope). By this the bag
becomes somewhat puckered above and below, but smooth by the arms.

The pocket, which in front is 400 meshes in circumference, is sewn
on to the hindmost horder of the forepart of the bag (consequently 400 meshes);
it is funnel-shaped, 7d meshes long and 100 meshes in circumference in the
hindmost, detached opening.

The hinder part of the bag is c. 2253 meshes long and 400 meshes in

16

circumference, all through; but, if we want it, a narrower end-piece may be
added (Cmp. fig. 6). The bag is open in one corner only, and can there be
closed with a tie.

The pocket can he put together of two machine-tied pieces; but generally
it is tied by hand, of light, strong, fine cotton yarn, as it must be very casily
movable in the water. If it is hand-tied, it is necessåry to »narrow« in it;
otherwise there will be no narrowings at all in the whole seine, and it can there-
fore easily be made of square, machine-tied pieces of yarn.

The arms and the forepart of the hag have meshes which, stretched out,
are c, 20 mm long (40 mm in circumference); the meshes in the pocket and the
hinder part of the bag are 16 mm long (32 mm in circumference); the thread
is everywhere (except in the pocket) 9-threaded cotton No. 12.

A still narrower part can, as ahove mentioned, be added to the hag, for
instance of meshes of 11 mm (22 mm in circumference); hut this depends on
the use you want to make of the seine. —

The meshes of the arms are sewn on to the ropes (alike for both), head-
rope and foot-rope, in such a way that, on the half-part nearest to the mouth,
6 meshes are carried in on each »hitch« of 4 meshes' length, i. e. on 80 mm;
and on the outer half 6 meshes on cach »hitch« of 86 mm. The length of the
bag becomes c. 16—18 feet.

The ropes are of equal length, c. 24—28 feet; but the lower one must be
much heavier than, the upper one, for instance 3—3"/, inches round, and both
had better be made of loosely laid rope, so that they do not kink. The whole
apparatus must stand quite smooth in the water, particularly the arms near
the mouth, without any puckers from above downwards; in the bag, by the
mouth, on the other hand there will come many puckers lengthwise. Accuracy
in sewing the meshes on to the ropes is most necessary, and if the latter become
longer by use, the net must he unsewn and sewn on again; particularly if the
ropes do not stretch equally much.

In order to give the seine the correct position in the water, weights are
attached to the foot-rope, and floats to the head-rope. The greater the weight is,
the harder the rope will drag along or in the bottom; the more weights,
the more equally the gravity will be distributed. I have found ca. 39 little
stones suitable, in straps of 2—4 inches in length. The distance between the
stones at the mouth must be a little shorter. At first we used a float made of
wood, c. 40 little pieces; they must be placed near the mouth, so that the
latter can be lifted up well in the water; afterwards I have only used float-
glasses (the Norwegian floats), and no doubt it will be right to use float-glasses

only as floats; they can bear the pressure of the water even down to 3000

fathoms (cmp. Tanner, loc. cit. p. 355), and do not change their specific grav-

ity, such as wood or cork, which already on a depth of a few fathoms is

pressed full of water, and so looses its power of lifting the net. Each glass-

balloon can bear about "/, Ib. of lead in the water, and I have found it suitable

to put on just so many balloons that they can bear the weight, which is tied on,

in thewater. The seine will then sink on account of the net itself and ofthe boards.—-
It is a most important thing that the seine is well balanced, and balanced

to fish on that bottom on which we want to use it. It is apt to be too

heavy, so that it gets filled with mud. (See ante, however, p. 13, as to the use

of a coirrope). With glass floats, tied up in meshes of

spun yarn, the balancing can very easily be managed on

shallow water, and the whole apparatus can there be prop-

erly arranged. Its specific gravity will then not change Duet

perceptibly on the great depths, as with cork or wood. I

have found ca. 30 glass-balloons, and a weight of 14—16

lbs. under water, suitable.

The boards are made of deal boards, ”/, inch thick, | |
with two long iron bolts through them. They are c. 29 inches
É Øg = Fig. 7. The vertex of
high and 32 inches long, or longer. At first we used small- Re EO RESTE

shackle and lead to

er boards, but these fish incomparably better. They are SEE Ane lene

bound with iron below, so that they smk as quickly as you Er NOE
want them to. On account of the distribution of the weight
(with iron below), they will remain in an upright position when they reach the
bottom, and they always sink through the water upright, just as the arms of the
seine. When they are suspended in the thimble which is placed in their four-
branched crow-foot, they must point down a little with their fore-end. The ropes
of the arms are fastened to the hind-edge of the boards in two holes, so that the
arms sit on the owrside of them. From a little in front of the centre of the boards
the two bridles of the crow-foot proceed (Cmp. fig. 5-—6.) The latter was made of
wire, and each bridle was c. 8 fathoms long. At first we used a shorter crow-foot,
but it is a great question whether it ought not to be still longer. (Ås to this, see
farther on). In the vertex of the crow-foot is a shackle, in one eye of which the
tow-rope is fastened. To prevent the bridles of the crow-foot from twisting
together, as they are inclined to, a lead (of ec. 5 Ibs.) is fastened to the under-
most, movable eye of the said shackle, so that it hangs downward in a short
strap. This prevents the twisting (Cmp. fig. 7).

Ås soon as the bag and the arms have got into the water, and the boards

3

ag

zæ (LIBRARY

18

have been lowered, while the vessel goes on quite slowly, the whole apparatus
immediately places itself in the right position, with the boards removed c.
12—16 feet from one another, so that you can see in the surface of the water,
whether the whole apparatus is clear. When you then veer, in such a way that
the tow-rope does not run out too quickly, the gear will always get clear to
the bottom; if not, the bag may, when the arms are veered down over it,
twist round the latter, or one board may fall down over the other. Such a
thing, however, happened only in the beginning.

As above mentioned, I suppose that the boards, with the usual, suitable
speed (about 1 knot), are 12—16 feet removed from one another. The seine,
therefore, gapes as widely as the common trawls for scientific use, even in
the largest vessels. The height of the mouth is c. 3—4 feet in the water, con-
sequently considerably greater than in the said trawls (c. 2 feet). The length
from the boards to the end of the bag is c. 40 feet, against a total length of
17—20 feet im the trawls, and yet this apparatus may be employed easily
from the smallest steam-boat that can only tow it, or from a little sailing-vessel
of 5 tons.

It would be desirable to compare the fishing capacity of the otter-seine
directly to that of one of the common deep-sea trawls; but I have been unable
to do so. The seine, however, has fished most excellently; on shallow water,
for instance, lots of Eels, Cod, Whitings, various species of flat-fishes etc., and
on deeper water, Coryphænoides rupestris, (Gadus poutassou, Gadus morrhua,
Gadus Esmark, Merluccius, Argentina, Chimæra, Lycodes, Myxine, Rays,
large Pandalus, Hippolyte, Nephrops, Pasiphaét, Nyctiphanes, Cuttle-fish, and a
great many other smaller, quick animals. But the thing which in my eyes
is the most important in this matter, is, that the apparatus, without being
perceptibly more difficult to manage, can be made still larger and consequently
be able to catch much more, and to catch other of the quick animals which now
escape it. For use in another year I have had a seine made which is a little larger
im all the meshes and whose bag is 500 meshes in circumference, the arms,
at the bag, being 120 meshes deep and 300 meshes long. —- If we prefer the
400 meshes, as in the above described seine, it is not necessary, however, to
make it exactly like that in order to get a seine that fishes well. The fisher-
men are said, for instance, often to make the arms 120 meshes deep, instead
of 100; in this wav the 6 »hitches« at the mouth are made smaller by 20
meshes, above as well as below. There is no small difference between the eel-
dragseines in the various parts of the country with respect to the size and
number of the meshes, the sewing on, etc., conditioned by the size of the

19

boats, the height of the vegetation, and so forth, but in their broad features
they are very like each other in their general appearance and form. — If we
choose to make the meshes larger, we can get a very large apparatus, which
can be dragged with much greater speed and, consequently, fish much quicker
and catch larger animals; and we are not troubled with clay, mud, and those
smaller animals and shells which we, otherwise, are too apt to get. For be it
remembered, with a small-meshed apparatus, however large it may be, we can
drag only very slowly. With great speed it will drive the water along in a wave
that washes away everything and frightens all quick animals, before they are
within reach; small meshes necessitate slow sailing; with large meshes we can
and must go on with a good speed. To keep the right speed is a very necessary
thing, which requires great practice and experience. Indeed, for every new
apparatus we must practise on low water, where the catch can easily be com-
pared to that of the older well-known apparatus. Every fisherman knows how
necessary it is to make a new eel-dragseine perfectly »fishable«, and I have
heard the same said of the large English trawls. It holds good, probably, of
any seine which is constructed with some fineness, and which is intended
really to fish as well as possible. An ordinary dredge or a »scientific« trawl,
on the other hand, can be used by everybody. They are extended by means
of heavy iron frames, and are anything but »fine«. Yet, also here there are
certain things to be observed; the claims to practice and experience in fishing-
technicalities, however, are reduced to a minimum; their fishing-capacity is,
accordingly, not very great. Nevertheless, we must not forget that great ad-
vantages are connected with them, on a difficult bottom and for certain pur-
poses. Å universal fishing-gear which is equally good under all conditions
and for any fishery, is not known and will never be known; the dredge and
the small scientific trawls, however, have been employed only too much
as such.

It will have been observed that the here described otter-seine approaches
very near indeed to the new English Patent Otter-Trawl; only, it is dragged
in a single line with a crow-foot, which must be the case with theflatter also,
if they were to be used on deep water. The greatest difference between them,
irrespective of a great number of details in the construction of the net itself,
is, that the trawl has shorter arms than the seine, that its foot-rope is longer
than the head-rope, and that its bag is tapering towards a point, while the
bag of the seine is nearly of the same width throughout its whole length. I
shall not attempt to discuss whether these differences are advantages or draw-
backs, whether, in other words, we ought rather to make otter-trawls than otter-

20

seines for scientific fishery: for the time present I am able to make and to
use the latter only. But supposing we want to keep the small meshes, c. 1
inch stretched out, !/, inch square, and as a rule I think we do so, we have
the advantage that the sewne in »practical life« has just such meshes, while
those of the trawl are much larger; and although, within certain limits, we

Fig. 8. The Albatross trawling. (After Tanner.)
(The tow-rope is shown lifted up from the bottom in its whole length; its most advantageous position.)

may change the size of the meshes in both gears, it is a great question after
all, whether a seine will fish well with very large meshes and a trawl with
small ones. If anyone wants to use a trawl, because he knows it better, there
is thus scarcely any essential reason to prevent him. Yet, if the meshes become
very small, I just call the attention to the fact that the bag of the seine is
larger both in circumference and in length, and suffers larger volumes of
water to pour through, than the pointed end of the trawl; and a great mass

of water must be able to pass through, if the fish are to get im here, just

driven by the current. — The pocket is one of the things in the seine which
must be shaped most accurately. It must be longish, funnel-shaped, without
any folds, and with a mouth (at the farther end) which can be extended
as more or less water runs through it. Therefore there must not be any
tie in the mouth either, only meshes, which can be extended of their own
accord, as the force of the water becomes greater while you go on. If you
stop, the pocket must collapse, and so prevent the escape of the fish which are
already caught.

ÅA drawback to all sorts of fishing-gear on deep water is that the tow-
rope, which is always of steel-wire, does not go directly from the fishing-
apparatus up through the water to the vessel, as it is often pictured (see for

Fig. 9. A Double-Trawl (front-view).
The dotted line shows the crow-foot in the unfavourable position, ihe line fully drawn out shows the same
in the favourable position. (About the same scale as fig. 10.)

instance Tanner: loc. cit. p. 365. & fig. 8); it is generally dragging along the
bottom in front of the gear, putting in motion the loose mud, by which all
shy animals are frightened away. (Comp. fig. 5.) Perhaps this matter has not
been sufficiently considered, for I have nowhere seen it mentioned more
closely. lf we imagine ourselves standing in front of such a »scientific« trawl
while it is working on the bottom, we shall see something like fig. 9 & 10,
where the dotted lmes show the crow-foot with shackle and tow-rope. We see
immediately that the position of these lines is very unfavourable, as they bar

a part of tbe fishing opening. On low water, 2—5 fathoms, where the vertex

of the crow-foot does not touch the bottom, because we can here take care to
veer out as little rope as necessary, the ropes sit, as shown by the fully drawn
lines in fig. 3—10. The fish perceive nothing at all till they are between the
arms of the seine, consequently till they are nearly caught; but on deep water
when the vertex of the crow-foot touches the ground, the fish must swim over
the bridles of the crow-foot before they get into the seine. The fishermen's

22

tow-ropes always stand in the favourable position, partly because they drag in
two separate lines, partly because they come on lower water only (under 100
fathoms).

It is therefore, evidently, a matter of great importance to lift the crow-
foot and tow-rope from the bottom, in such a way that they do not prevent
the fish from getting into the trawl. I cannot say precisely, how it can be

done on deeper water, but I shall mention some momenta which influence this

Fig. 10. An Otter-Seine (front view).
The dotted line shows the crow-foot in the unfavourable position, the line fully drawn out shows the same
in the favourable position. (About the same scale as fig. 9.)

matter. If the otters of the seine are very heavy and the crow-foot with the
tow-rope proportionally light, there will be a tendency towards lifting the latter
two from the bottom, provided that we do not veer out too much line; and if
we could make both bridles of the crow-foot very long, for instance 100 fathoms,
we should, I dare say, within certain limits, be able to manage it in such a
way that the vertex of the crow-foot never went to the bottom. But if we
make the crow-foot too long, it is difficult to heave it in, and it is liable to
twist together, because the angle between the bridles becomes smaller, the

longer the bridles are; this twisting can be counterworked, however, as above

23

mentioned, by attaching a lead to the shackle (see fig. 7), but then again the
whole thing becomes heavier. I have therefore, in 1898, counterworked the
twisting by tying three floats of glass to the shackle, which by their upward
pull evidently counteract the twisting as well as a downward pull. I imagine
that we, after some experiments, shall be able to construct these floats in such
a way that they actually keep the crow-foot in the turned-up position which
we want. (Comp. fig. 7 (dotted] and fig. 5 [fully drawn out|). The difficulty is
only to get the weight of the crowfoot and the otters duly apportioned —
the former is to weigh hut a little, the latter much — and to get a float of
suitable size. Perhaps neither the crow-foot nor the first part of the tow-rope
ought to be made of steel-wire, but of a material of a lower specific gravity. It
is scarcely worth the while, however, to talk much of this as yet; I only set
forth the thought for the further consideration of those who might be inclined
to make experiments upon the matter.

As to the condition of the bottom, it is a well-known fact that it is of
the greatest importance with respect to the applicability of the trawls and the
seines. Å sharp coral-bottom or sharp stones which tear everything to pieces,
or take hold of the foot-rope in such a way that it cannot get loose again,
make any such fishery impossible. If the stones are round or partly hidden in
the bottom of the sea, the otter-seine may very well he used; it is pretty well
adapted to get over such stones, particularly with a coirrope (see ante), as it
falls together by eontinued pulling, so that the otters approach one another.
On a hard sand-bottom the otter-seine fishes excellently, also where the bottom
is covered with Zostera. On a soft bottom (mud) you will always be able to
drag with a »scientific« trawl; but whether it will go down into the mud and
be quite hidden by this, or whether it will skim the surface as it ought to, is
a thing you cannot know or decide beforehand; for its frame is and must
always be heavy. By means of a coir-rope, however, you can always make
the seine go lighter across the bottom, and owing to the oblique position of
the otters they can never sink deep down, not even in very soft mud; also in
this respect, in my opinion, the seine has a great advantage over the »scienti-
fic« beam-trawls. —

In concluding, I shall still mention a very important thing with respect
to the use of such apparatus, i. e. their preservation. Our fishermen always
use pure coal-tar for the preparation of their eel-dragseines, maintaining —
and according to my experience they are right — that if the seines are not
quite stiff with coal-tar, they cannot catch well. The pocket only must not get
too much coal-tar; as above mentioned it must be light, it must take its right

24

position, in funnel form, at the slightest motion of the water, and when the seine
stops its progress across the bottom of the sea, it must collapse and so prevent
the fish from escaping out of the bag; but the arms and the bag must be
stift with coal-tar, so that they will always stand up and make no folds.

The fishermen always employ heat for making the coal-tar thin, before
the apparatus is dipped into it. According to my experience it is easier and
better to make it thin by mixing it with ereosote-oil (carbolinium). The tar
can then be used cold, and enters better into the strands. When, by much
use, the tar is worn away so far that the strands may become saturated
with water, the treatment must be repeated. To prevent wear and tear where
it is worn most, i. e. on the under side. of the hag, an extra piece, made of
yarn, is fastened to the outside, so that the hag here really becomes double;
but it is necessary to sew on this piece carefully, so that it does not prevent
the bag from taking its right shape in the water. —

Ås pointed out above, -it is not my opinion that we shall rest satisfied
with the here described apparatus for the investigation of the unknown seas;
but I have wished to point out a way which has not hitherto been successfully
trodden by any explorer, and which makes it possible easily to modify the

apparatus with due respect to the various problems that are to be solved.

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