1911 Encyclopedia Britannica
Seining and Netting Trawling
The innumerable kinds of fishing nets which may be distinguished, if all nets differing in details of structure or use be placed in separate classes, fall naturally into two main groups, namely stationary nets and nets used in motion. The former group contains the most primitive nets, though nets of great complexity are now included in it; and the simplest fixed nets, themselves derived probably from dams of rushes or stones so placed as to lead fish in to a " pound " or enclosure, may with some confidence be considered as the ancestors of the great otter trawls now shot and towed daily from powerful steamers on fishing grounds more than a thousand miles from the market they work to supply. The more primitive fixed nets are of far less importance than movable nets (except in the capture of certain particular species), owing to the fact that they are necessarily confined to very shallow water. The main types of movable nets may therefore be treated first.
All nets are constructed in accordance with what is known of the habits of the fish they are designed to capture; and as fishes may be roughly divided into those spending at least the greater part of their lives on or near the sea-bottom and those spending a great portion of their lives near the surface, two lines have been followed in the development of nets, some being designed to work on the bottom, others to work near the surface. The most important nets used in the capture of " demersal " or bottomliving fishes are trawls; the most important pelagic nets are driftnets. The word trawling i was at one time applied to more than one method of fishing, but has, at all events in Europe, now become restricted to the operation of a flattened conical net or trawl, dragged along the sea-bottom. There are two trawls in common use, the beam trawl and the otter trawl. They differ in the method adopted for extending the mouth of the net. The original form is the beam trawl.
The beam trawl may be described as a flattened conical net whose mouth is kept open when in use by a long beam supported The at the ends by iron runners, the trawl-heads. Elm Beam Trawl. is generally preferred for the beam, selected if possible from timber grown just to the proper thickness, that the natural strength of the wood may not be lessened by more trimming or chipping than is absolutely necessary. If the required length and thickness cannot be obtained in one piece, two or even three pieces are scarfed together, and the joints secured by iron bands. The trawl-heads differ somewhat in form in different countries and in different localities. The usual form is heartshaped, the " shoe " or part actually in contact with the ground when in use being straight, the after-side straight and sloping upwards from the hindmost point or " heel," and then curving down in a single unbroken arc, which forms the front of the head, to join the shoe. In the Barking pattern the head is stirrupshaped; but this is now unusual. A square socket is bolted to the top of the head (taking the head to be in the position of use) to receive the end of the beam, and ring-bolts are put in at the extreme front of each head, to hold the ropes or wires by which the trawl 1 " Trawl " is from 0. Fr. trauler, to go hither and thither; " troll," now used of drawing a line along the surface of the water from a boat, is from the variant 0. Fr. troller, mod. troler, to lead, drag about.
is towed, and, within - the point of the heel, for the purpose of allowing the mouth of the net to be seized or lashed to the trawl-head at a point close to the ground. The shoe of the trawl-head is in the full-sized trawls made of double thickness, to resist wear.
When the net is spread out in the position it would take up when working, the upper part or back has its straight front edge fastened to the beam, but the corresponding lower part or belly The Net. is cut away in such a manner that the front margin forms a deep curve extending from the shoe of one trawl-head to that of the other, the centre of the curve or." bosom," as it is called, being at a considerable distance behind the beam. The usual rule in English trawls is for the distance between the beam and the centre of the bosom to be about the same as the length of the beam. In French trawls this distance is generally much less; but in all cases the beam and back of the net must pass over a considerable space of ground when the trawl is at work before the fish are disturbed by much of the lower margin of the net. This lower edge of the mouth of the trawl is fastened to and protected by the " ground-rope," which is made of an old hawser " rounded " or covered with small rope to keep it from chafing, and to make it heavier. The ends of the groundrope are fastened at each side by a few turns round the back of the trawl-heads, just above the shoe, and the rope itself rests on the ground throughout its entire curve. The fish which may be disturbed by it have therefore no chance of escape at either the sides or top of the net unless they can pass through the meshes, and as the outlet under the beam is a long way past them, and is steadily moving on, sooner or later they mostly pass over the groundrope and find their way into the funnel-shaped end of the net, from which a small valve of netting prevents their return.
It must not be supposed, of course, that all fishes entering a trawl are retained in it. Numerous investigations have been made into the size and number of the various species of fish which get through the meshes of the trawl, by lacing small-meshed netting over the ordinary net, and examining the fish remaining in this outer net. Fish are found to escape all parts of the net, but chiefly the " batings, " i.e. the part of the net where it is narrowing to the " cod end "; and as the chance of escape depends on the size and shape of the fish, and the mesh of the net, it is naturally found that the maximum size of the individuals which can escape in any numbers differs in different species. If small fish are on the ground, the total number escaping is, however, in all cases very large, frequently greatly exceeding the number caught. This is for the most part desirable, the fish being of a size to render them of but little value to the fishermen or to the public. It is in any case inevitable, since a full-sized trawl made entirely of small-mesh would offer so great a resistance to the water as to be unworkable.
The ground-rope bears directly on the ground, and to prevent the possibility of the fish passing under it, the rope should have some weight in it so as to " bite " well, or press the ground closely. It is, however, always made of old material, so that it may break in case of getting foul of rocks or such other chance obstruction as may be met with on the generally smooth ground where the trawl can only be worked with advantage. If in such a contingency the rope were so strong and good as not to break, there would be serious danger of the tow-rope snapping, and then the whole apparatus might be lost; but the ground-rope giving way enables the net to be cleared and hauled up with probably no more damage to it than the broken rope and perhaps some torn netting. The remaining part of the trawl, extending from the bosom to the extreme end, forms a complete bag gradually diminishing in breadth to within about the last 10 ft., which part is called the " cod or purse," and is closed by a draw-rope or " codline " at the extremity when the net is being used. To avoid the abrasion of the under part of the cod-end pressed by the weight of fish against the stones and shells of the sea-bottom, stout pieces of old net are laced across beneath it in parallel strips. These strips thus trail beneath the trawl and protect it. They constitute the " rubbers " or " false belly." The cod-end is the general receptacle for the various fishes which enter the net; and when the trawl is hauled up and got on board the vessel, the draw-rope is cast off and the fish all fall out on the deck.
It has been mentioned that the body of the net tapers away to the entrance to the purse. It is at this point the opening of the pockets are placed; and they are so arranged that the fish packets. having passed into the purse, and then seeking to escape by returning along its sides, are pretty sure to go into the pockets, which extend for a length of about 15 or 16 ft. along the inner side of the body of the net, and there, the more they try to press forward, the more tightly they become packed, as the pockets gradually narrow away to nothing at their upper or front extremity. These pockets are not separate parts of the trawl, but are made by merely lacing together the back and belly of the net, beginning close to the margin or side nearly on a level with the bosom, and then being carried on with slowly increasing breadth backward as far as the entrance to the purse. At this point the breadth of the net is divided into three nearly equal spaces, the central one being the opening from the main body of the net into the purse, or general receptacle for the fish, which must all pass through it, and those on each side being the mouths of the pockets facing the opposite direction. The central passage has a valve or veil of netting called the " flapper," which only opens when the fish press against it on their way into the purse. To understand clearly the facilities offered to the fish to enter the pockets, it is necessary to remember that the trawl, when at work, is towed along, with just sufficient force to expand the net by the resistance of the water. But this resistance directly acts only on the interior of the body of the net between the pockets and then on the purse; it does not at first expand the pockets, but tends rather to flatten them, because they are virtually outside the general cavity of the trawl and their openings face the father end of it. The water, however, which has expanded the body of the net, then passes under or through the flapper or valve, and enters the purse, which, being with a much smaller mesh than the rest of the net, offers so much resistance that it cannot readily escape in that direction; return currents are consequently formed along the sides, and those currents open the mouths of the pockets, which, as before mentioned, are facing them; and the fish, in their endeavours to escape, and finding these openings, follow the course of the pockets until they can go no farther. The whole of the net is therefore well expanded, but it is so by the pressure of the water in one direction through the middle, and in the opposite direction at the sides or pockets.
The dimensions of a full-sized beam trawl, such as has been described above are from 45 to 50 ft. along the beam and about and too ft. in length. Trawls of practically all smaller Size s i zes down to some 30 ft. are to be found, but except Mesh for shrimp trawls the large sizes predominate almost to the exclusion of smaller nets. The trawl-heads support the beam at about 3 or 32 ft. above the ground. The meshes of the net behind the beam (the square) are about 5 in. from knot to knot, when drawn out taut. In the batings, the part of the net in which the narrowing mostly occurs, 'they decrease gradually from 4 to about 3 in.; in cod end they are 22 in. In the hope of protecting the small fish from capture some local authorities enforce within their jurisdiction a minimum size of mesh for trawls, as for other nets. According to certain recent by-laws of the Lancashire and Western Sea Fisheries District Committee, for instance, every trawl used in their waters, except for the capture of shrimps and certain specified fish, must allow a square wooden gauge of a certain size to pass easily through its meshes when these are wet. The difficulties in the way of the efficacy of such restriction are that a mesh which would allow the escape of fish of but little value of one species might allow the escape of very valuable individuals of another kind; and that both local and national authorities alike have powers of jurisdiction over such narrow strips of coastal water, that in the absence of an international agreement on the matter, the ground affected by the regulations is exceedingly small in comparison with the ground untouched. The same remarks apply to the similar regulations as to length of beam and circumference of nets.
Considerable skill is needed to work a beam trawl successfully. A knowledge of the ground and of the direction and time of the Working tide is essential; for the trawl is towed with the stream, Net. a little faster than it is running, that there ma be the j ust sufficient resistance to expand the net. The regu lation of speed, seeing that beam trawls are worked only from sailing vessels, is a matter of difficulty; when, however, there is a sufficiency of wind much can be done by an adjustment of the length of tow rope. Lowering the trawl is also a matter of difficulty especially when wind and tide are contrary, as in that case the vessel tends to drift over the net: the apparatus is first got into position by paying out the rope attached to the trawl-heads in such proportions that the beam takes its proper position while close to the surface. These ropes, called " bridles, " are some 15 fathoms long: they meet and are shackled to the trawl warp, a manilla rope of 6 in. circumference, of which 150 fathoms are generally carried. The trawl being in proper position, the warp is allowed to run out and the trawl lowered to the bottom, the vessel slowly moving on meanwhile; usually the length of warp which is below the surface in towing is a few fathoms over three times the depth of water. The art of shooting the trawl lies in causing it to alight on its runners or shoes, with the net freely trailing behind: should the net be twisted, or the trawl alight on its beam, the trawl has been shot " foul, " and must be hauled and shot again. While towing, an experienced fisherman can tell by pressing his hand firmly on the warp outside the ship's bulwark whether the progress of the trawl over the bottom is satisfactory, any irregular progress over rough ground revealing itself in the character of the vibration of the warp.
The trawl usually remains on the bottom for a whole tide, or six hours, and will in this time have passed over some 15 m. of ground. Hauling, a most lengthy and laborious process if carried out by hand-windlass, is in practically all modern fishing smacks carried out by a small steam capstan, the " steam man " as it is frequently called, a most efficient instrument with very compact engine housed under a small iron cover on the capstan's top. When the trawl comes alongside the heavy beam is secured by its two heads, the net is hauled over the side bit by bit, by hand, until the cod end is reached, when a rope is passed round it above the bulging end which contains the catch, and then over a " tackle "or pulley, and so the cod end is hoisted inboard. The knot of the codline is untied, and the fish, mixed with various invertebrate animals, star-fish and rooted forms (confounded in the one term " scruff "), falls to the deck.
A small trawl is often used from an open boat for shrimping. It closely resembles a beam trawl, but has no pockets. The usual dimensions of this net are about 15 ft. beam and 20 Shrimp total length, of which about 4 ft. are taken by the cod Trawls. end. The mesh is about half an inch square, but where no restrictions are enforced it decreases to a considerably smaller size as the cod end is approached. The beam when in use is about a foot and a half above the ground.
Shank nets are also similar to beam trawls in general shape, but differ in that the mouth is kept open by a rectangle of wood. Frequently the lower margin of the trawl's mouth is Shark Nets. not in contact with the ground, being attached to a bar of wood which is fixed parallel to the bottom of the wooden rectangle and a few inches above it. A fish or prawn is thus disturbed by the bottom bar of the wood, and either jumps over it and below the net and so escapes, or over both bottom bar and middle bar into the net. The theory of the net's action is that the fish tends most frequently to take the former course, the crustacean the latter; and there is some evidence that this is partially realized in practice. Shank nets are sometimes worked from carts, when they are known as " Trollopers." Owing to their fine netting and the very shallow water in which they work, shrimp trawls are exceedingly destructive to very small fish. Johnstone 1 has found for instance that in a two mile haul of a shrimp trawl on the Lancashire coast 567 small plaice are caught on an average, beside great numbers of whiting, dabs, soles and other fish. In most parts of the English coast regulations are in force as to the mesh, size of beam and length of haul of shrimp nets, and shrimpers working on the beach are ordered to sort their catch at the water's edge, returning as many young fish alive as possible. The proportion saved by these means is not known with accuracy; it is much greater in the case of short hauls than in longer ones. A shrimp trawl is usually kept down from half an hour to an hour, or when not subject to regulation rather longer. It is seldom towed for a longer period than 2 hours, the speed being somewhat under two miles per hour on an average, though subject to variation.
The beam trawl has been described at some length because its structure is somewhat more simple than that of the trawl now in more general use; the importance of the net Decay of as an engine of capture has undoubtedly declined Beam greatly within the past generation. Some interest- Trawling ing figures collected by the British Board of of other Agriculture and Fisheries prove this incontestably. Trawling In 1893 the number of first-class British sailing from trawlers was 2037, and their average net tonnage Steamers. 57.4; in 1900 they numbered 925, with a net tonnage. of 41.1, and from that year up to 1906 (the last year quoted in these returns) they never again reached a thousand in number or a tonnage of 40 tons net; on the other hand, there were in no one of the years quoted as few as Soo first-class sailing trawlers registered, nor did the average tonnage sink below 37, about which figure it remained constant. It is obvious therefore that about 1894 beam trawling began to decline, and that after a time this decline lost most of its power, the number of boats and size of boats having sunk to a condition in which they fulfilled a certain function, which for some years has remained fixed. The new factors which brought about this change went hand in hand. They were the invention of the otter trawl and the increasing use of steam in fishing vessels. The otter trawl has no rigid and heavy beam, but relies on the force with which it is towed through the water to keep it open, and it is a far more efficient instrument for the capture of all but small flat fish than the beam trawl. Owing to the second of these facts its employment inevitably spread, and owing to the first a sailing vessel needing at least a moderate breeze to give it the requisite speed for keeping a large net open was unsuitable for working it. Thus the introduction of the otter trawl undoubtedly hastened the replacement of sails by steam as motive power for the great fishing fleets. That the adoption of steam would have occurred in any case is almost certain. The conversion of drift-net fishing vessels from sail to steam has gone on rapidly, though no radical change of gear has taken place, and presumably the same would have occurred in the case of trawlers had the otter trawl never have introduced. There 1 Johnstone, British Fisheries, p. 283 (London, 1905).
were, for instance, nearly zoo steam fishing vessels of various descriptions working from English and Welsh ports in 1883; and the desire to exploit new and more distant grounds had undoubtedly become powerful by 1894, and accounted to some extent for the increase of steam trawling about that time. Nevertheless this increase is so sudden, that its occurrence at the time of the adoption of the otter trawl can scarcely be a coincidence. In 1893 there were 480 steam trawlers working from English and Welsh ports: in 1899 there were over a thousand.
The subsequent history of British trawling is dominated by the steamers. Garstang has calculated from a study of market statistics that a steamer (between the years 1889 and 1898) caught on the average between four and seven times as much in a year as a sailing smack. Against this competition the smacks could not succeed; if it was profitable for the steamers to fish they could gradually eliminate the smacks, as has occurred at Grimsby. The line fishery also decreased owing to the increasing transfer of the haddock and some other fisheries to the trawlers. The change from masts and sails to steam has, however, never been complete. The increased cost of building and running steamers made the handling of large catches a necessary condition of their profitable employment. A sailing trawler costs from 500 to £1200 to build: £1000 would probably be a fair average. A first-class steam trawler of the present day costs £io,000 or more, quite ten times as much, and about 5000 a year to run; and although the cost was less in the early years of steam trawling there was always an approach to these proportions. On the other hand their rapidity and independence of wind made distance between fishing ground and port of landing a matter of minor consequence. These causes, combined with a very general belief in the exhaustion of the home-groundsthere seems no doubt that at all events the catch per vessel declined - led to the growth in size and power of the steamers, which were used for distant waters and the exploitation of new grounds. Thus in 1906 there were only 200 more steam trawlers than in 1899, but the average tonnage in the same period increased from 54 to nearly 62. To this increase in power and range of action of the steamers must be attributed the great increase in the quantity of trawled fish landed, since the engine of capture, the trawl, has changed but little since 1894: but another result occurred, namely a partial division of the area trawled between sail and steam. The grounds within easy reach of the English ports were left chiefly in the hands of the " smacks," the catches never being really very great, though possessing a high proportion of " prime " (i.e. valuable species of) fish. The persistence of Lowestoft and Ramsgate as smack ports speak for this. The longer voyages of the smacks, on the other hand, were gradually discontinued, and the distant grounds besides a multitude of new grounds were opened up by the steamers. Grimsby, Hull, Aberdeen, Milford, increased enormously in importance, and now send vessels to the north of Russia, to the coast of Africa and far into the Atlantic. Steam trawling died at Yarmouth, the place of its birth; sailing trawlers disappeared from Grimsby, one of their greatest strongholds, but a port near cheap coal, deep water, and a market for fish from more distant grounds.
FIG. I. - Diagrammatic; showing an Otter trawl in use. (For the sake of clearness, the size of the otter-boards is exaggerated, and the length of the warps and size of the ship diminished.) The essential features of the otter trawl are that the mouth is kept open by two large wooden boards, whose position when in use corresponds to that of the trawl heads in a beam trawl no beam being used. The action of these boards The Otter resebles that of a kite. A kite dragged through Trawl. m still air, owing to the position of the point of attach- Principle ment of the string, takes up an oblique position, in of Action which it is acted on by forces in two directions, viz. that exerted through the string, pulling forward, and that exerted by the resistance of the air in front of the kite, which, being perpendicular to the kite's surface, acts in an upward and backward direction. The resultant of these two forces necessarily acts in a direction between them, and the kite accordingly ascends. Constrain the kite to move in a horizontal plane, and the same forces would cause it to move not upwards, but to the side. A trawl board is practically a kite made to move on its side.
The trawl boards resemble massive wooden doors strengthened by iron bands. In action they move with their short edges vertical and their long edges horizontal, one in each case in contact with the sea bottom: the front bottom corner of each board is rounded off, so that the board resembles a sleigh runner. Four strong chains, which meet in one iron ring, are attached to each board by ringbolts, and to each ring a wire warp, by which the trawl is towed, is shackled. The ringbolts are about the same distance from the centre of the board, but the two chains attached to the after-ringbolts of the board are longer than the two fore-chains. The trawl board when towed thus takes up an oblique position as regards the line in which it is towed, though remaining vertical to the ground. The force with which it is towed urges it forward, the resistance of the water urges it in a direction perpendicular to its surface, viz. backwards and to the side; it accordingly moves in an intermediate direction, going forward by tending to diverge from the line of towing. Meanwhile the other trawl-board is diverging in a similar manner but in the opposite direction, and the mouth of the net, being attached to the hinder end of the boards, is thus pulled both right and left until stretched to its utmost, and the net is thus held open. The margin of the net which forms its upper lip is lashed to a rope called the headline: and the resistance of the water to the net's progress causes this to assume an arched form, the centre of the headline being probably some 10 or 15 ft. from the ground.
It has been calculated by Fulton, who experimented on the subject, that the distance between the boards of an otter trawl of 90 ft. headline is about 60 ft., owing to this arching upwards and backwards of the upper margin of the net. The loss in the spread of the net is, however, compensated for very largely, as far as certain round fish are concerned, by the increase in height of the mouth, the fish which are swimming near but not actually on the bottom tending to "strike upward" when disturbed. Indeed, the raising of the headline is accentuated occasionally by glass spheres or other buoyant objects to its centre; corks are still used in this way, but otherwise the practice has not been generally adopted in commercial trawling.
The earliest use of the otter board appears to have been due to Hearder, an electrician and inventor who designed it about 1860. It was little used except by amateurs working by steam yachts (to whom doubtless the ease with which it could be stowed away recommended it), until the late 'eighties, when Danish fishermen used otter boards to spread their plaice seines. In 1894 a patent was taken out by Scott of Granton for an otter trawl which differed from the most modern forms chiefly in possessing rigid bars or brackets instead of chains. Chains replaced the bars in the form used by Nielsen, a Dane, in 1895. Although numerous variants have since arisen, no essential difference in the trawl has been generally adopted. The trawl boards, or as they are frequently called " doors," are of deal, 8 to 9 ft. long, and 4 to 5 ft. high; they are liberally shod and strengthened with iron, and are about 3 in. thick. Details of The net is fastened to eyes placed at the top and bottom structure. of the after-end of the board, but not to any intermediate The Boards. point. This is to allow the part of the water swirling past the board to escape: the entry of the whole of the water upon which the net's mouth advances would cause too great a resistance.
Two warps are used, one to each trawl board. These are composed of wire rope 21 in. round, and when the trawl is inboard lie coiled up on the separate drums of a steam winch. The Warps. As wire can be run off or wound in on either drum separately, the adjustment of the lengths is much simplified. In the larger trawlers a thousand fathoms of warp is carried on each drum, and the warp is designed to stand a breaking strain of 23 tons.
The main form of net is that of the beam trawl. We have, as in that net, a coarse meshed netting used near the mouth, a decrease in size of mesh as the net narrows, and a bag The Net or cod end whose end is fastened by a cod line passed through its final meshes. The only essential difference lies in the net behind the headline. This has not, as in the beam trawl, a straight margin, but a curved one, the pointed sides of the net being termed the "top wings" of the trawl, the corresponding parts of the bottom being in both trawls the bottom wings. The ground rope resembles that in the beam-trawl, but is in some cases furnished with chains or " dangles " or with " bobbins." Bobbins are heavy cylindrical wooden rollers, threaded on the wire warp which forms the core of the ground rope: they are of two sizes (the larger a foot through) placed alternately to ensure freedom of rotation. Their object is to surmount or crush obstacles which, by catching the ground rope, might capsize the trawl boards and destroy the success of the haul; they are accordingly used only on rough ground. The chains are fastened to the ground rope in loops, to give it weight, and are used on very soft ground to ensure the trawl's effectually dislodging the fish. The headline is a rope some 3 in. in circumference.
The meshes are, from knot to knot when drawn taut, from 51 to nearly 6 in. in the square and wings, 5 to 42 in. above, and 5 to rather over 3 in. below in the extreme back of the under batings called the " belly," about 21 in. in the cod end.
The successful shooting of the net is a matter of great skill. The paying out of the net, the lowering of the boards, the running out of unequal lengths of the two warps to square the trawl into proper position and the subsequent lowering of the whole to the bottom, resemble the corresponding operations with the beam trawl. The fore warp is then drawn close to the quarter of the vessel and shackled to the after-warp close to the vessel's side, and the vessel proceeds on her course at a speed of some 24 or 22 m. per hour. The length of haul made varies enormously. On a ground where fish is very abundant, as in the early days of Iceland fishing, it may be half an hour or less: on the Eastern Grounds, off Denmark, where the great English fleets usually work, it is about 3 hours. When about to haul, the fore warp is released from the shackle and the vessel is immediately steered towards the side from which the trawl has been towed, while the warps are rapidly wound in; the warps thus speedily come to stand at right angles to the vessel. If this were not the case they might probably foul the vessel's propeller, with very serious and possibly fatal consequences to her safety. The trawl boards, having been drawn right up to their powerful iron supports or gallows, remain suspended there if the trawl is to be re-shot while the net is emptied; they are otherwise lowered between the gallows and the bulwark, and secured. The hauling in of the catch occurs as in the beam-trawl. Trawlers carry a trawl on each side of the deck, and in continuous trawling these are worked alternately. On each side of the deck a square enclosure called a pound is made for the reception of the fish falling from the cod end, by fitting planks turned on their sides into stanchions grooved for their reception. The fish is sorted into baskets in the pound, cleaned and packed in trunks in ice in the hold or fish-room.
A noteworthy method of trawling is the custom of 50 or 60 boats fishing together in a fleet. All these vessels will trawl as directed by an " admiral," in proximity to a " mark. boat," whose position is known to the owners from day to day, and the fish is daily fetched to market by fast " carriers." There are four such fleets of British vessels working in the North Sea. It is also worthy of mention that wireless telegraphy has recently been fitted to several German trawlers and drifters, which can thus communicate with the fishery protection cruisers, who pass on information concerning the fishery, and with the shore. The practice will doubtless spread, although as yet the distance over which a message can be sent by these vessels is very small.
The use of steam has not only increased the radius of action of the vessel, but by facilitating the process of hauling enables trawling to be carried out in greater depths. The sailing vessels rarely work in greater depths than 30 fathoms.
The steam vessels work frequently (e.g. south of Ireland) in over 200 fathoms. Commercial trawling in 500 fathoms is not unknown, and the Irish research vessel " Helga " works in as much as 800 fathoms.
The movable nets resembling trawls are seines, from which trawls were in all probability developed. The seine is an. extremely ancient net, used by Phoenicians, Greeks and other Mediterranean peoples, the word seine being derived from the Greek name (aa'pjvn) for the appliance. In essence it is a long strip of netting with a buoyed headline and weighted ground rope. It is taken out in a boat some little distance from the shore, paid out during the boat's progress, and the lines attached to the ends being then brought back to the shore, the net is hauled up on the beach. From this simple form, which is still in use for the capture of smelts and other small fish, numerous developments have occurred. Before mentioning the details of a few of the chief of these it may be said that the changes mainly consist in the formation of a purse or pocket in the middle of the net, somewhat resembling the cod end of a trawl, and in the working of the net from boats or ships instead of from the sea.
The boat is anchored during the hauling, the net being drawn to it. A net with a wide spread, furnished with a purse, drawn over the sea bottom to a boat, is obviously very near a trawl in its action. When in the late 'eighties Danish fishermen fastened otter boards to their plaice-seines, and allowed the boat to drift, the seine was dragged by, not to the boat, and when Petersen used a similar arrangement, presently to be described, dragged like a trawl, the evolution of a trawl from a seine was practically complete. Some such process, with the use of a beam instead of otter boards, probably occurred in the past and resulted in the beam trawl.
Pilchard seines, as the most elaborate forms of simple seines, may be briefly described. The pilchards approach certain parts of the Cornish coast, notably St Ives and Penzance, in shoals which are eagerly awaited; and when they are sufficiently near two boats start out on the fishery.
One carries ,a short seine, the stop net, which has previously been joined to the large seine, and shoots this net as it rows towards shore. The other rows along the shore, shooting its net as it goes. Ultimately the boats turn to meet each other, and when they do so the ends of the long seine are joined, the stop net removed, and the circle of netting towed to the beach until its ground rope touches the bottom. The pilchards are then removed at leisure by a smaller seine called a tuck-net - seine being a word which in the west of England is confined to nets worked from the beach. This net is very deep in the middle, and as the foot rope is drawn well in in hauling, a floor is formed for it as it approaches the boat from which it is worked, a simple form of purse or bag resulting. The pilchards are dipped out in large baskets. In a good catch this process of " tucking " out the fish may be carried on for some days. The long seine used may be 200 fathoms long, and is about 6 fathoms deep at the ends and 8 fathoms in the middle. The tuck-net is about 80 fathoms long, 8 deep at the ends and to fathoms in the middle. The meshes are larger at the ends or wings than in the middle, as in the trawl, bringing a tuck-net from 30 down to 42 the yard.
The seine is far more used in the United States than in. the British Islands, its operations being so successful that complaints have in some cases been made that local fisheries for certain species have been entirely destroyed owing to the diminution of the fish which it has brought about.
It is used in water of any depth, for the purpose of catching mackerel. Rings are fastened to the ground rope, and by means of a rope passed through these rings the lower margin of the net is drawn together, converting the circle of netting into a complete basinshaped purse. The slack of the net is then gradually drawn in, the fish collecting in the last of the net (the fullness or " bunt ") to be reached. Purse seines are also used in Japan, where there is also in use a net which is a combination of seine and pound-net. A long wall of netting forms a " leader " to the fish, and ends in an oval enclosure formed by a purse seine with incompletely closed ends. Two anchored boats, to which the seine is lashed, keep it extended. On hauling, the opening is closed and the slack of the net hauled into one boat, which approaches the other, until the final portion containing the fish is brought to the surface.
The pockets of seines, though answering the same purpose as those of trawls in preventing the escape of the fish, « resemble not the pockets but the cod end of the latter w ith net. In the filets de bceuf of the Mediterranean the .» pocket is a very long bag, trailing behind the arms of the seine, and constricted for some distance before joining it. It is without " flapper " or other valve.
(After Drechsel.) FIG. 2. - Diagram of a Danish Plaice-seine at work.
Most efficient pocketed seines are used in Denmark for the capture of eels and plaice. In both these nets the depth increases rapidly as soon as the extreme wings are left, and is very great in the middle. Thus when in action but little of the net is vertical; the ground and head ropes, though not parallel, tend to become so, and the net trails in a curve behind them. Seen from Danish . above, the whole front margin of the net is semicircular, Seines but the net itself is shaped like the hinder part of a trawl: in fact, did the headline of a trawl lie not in front but exactly over the ground rope, the two nets would be almost identical. The eel drag-seine is worked from a boat, in shallow water. The extreme ends or wings are attached to two short spars, which Eel Drag in use are upright, and each of these is furnished with. a line top and bottom which meet and are attached seine to the ropes by which the net is hauled in. The total length of the net is about 140 ft. from wing to wing, the length of the bag 30 ft., the depth at mouth is 20 ft. opening, the depth at the ends 6 or 8 ft.
The eel drift-net resembles the preceding, but is not drawn to an anchored boat, but drifts with the boat; it has accordingly Eel Drift- to be made much smaller, its arms being each about net. 24 ft. - or a total length of 50. The wings were some times kept apart by the use of a floating spar,;.o the ends of which the seine was attached by short ropes, the spar itself being towed. A funnel-shaped valve leads into the bag.
Petersen's trawl was designed by Dr Petersen for use in deep water, and for the capture of rapidly moving animals. It is es sentially a drift-seine of the preceding pattern, worked Petersen's with two small otter boards instead of a beam, and Trawl, furnished with but a single warp, to which the otter boards are attached by shorter ropes or bridles. When used in very deep water these are prevented from twisting by attaching at the point of their junction with the warp a glass float and a leaden weight. This net is undoubtedly highly suitable for great depths. It is probably the " trawl " which it has been reported has been repeatedly used in the great depth of 2900 fathoms from the Norwegian research vessel " Michael Sars," in the course of the cruise in the Atlantic carried out in 1910 by Sir John Murray and Dr Hjort. It is practically a small otter trawl with the square cut out, leaving only wings, back part of batings and cod end, which last:is entered by a funnel of netting. The meshes, in the net first constructed by Dr Petersen, were about a centimetre square in the wings and 8 millimetres square in the bag. The arms were each 24 ft. long, the bag about 16 ft. The boards were 29 in. by 32 in., and 4 in. thick. Glass floats are frequently used with this trawl, to keep up the headline.
The Danish plaice-seine resembles the eel-seine in form, but is much larger, each arm being about 180 ft. long; the bag is 20 ft.
long. The drag lines are also much longer, sometimes Danish -seine. reaching to 1200 fathoms. These nets are worked Plaice from a very large number of boats, Esbjerg being the chief North Sea port engaged in the fishery. The vessels are yawl rigged, of the size of all but the largest smacks, and each is now furnished with a motor-boat. The boat takes the net to a considerable distance from the parent vessel, which is anchored, and shoots it in a wide curve. The drag lines are then brought back to the smack for hauling. By this method plaice are captured alive, and are kept in large floating fish-boxes until required.
Next in importance to trawling among the English fisheries is the use of drift-nets for mackerel, herrings and pilchards. Drift Nets. It is undoubtedly the most common method of netfishing on the coasts of the British islands, but nowhere is it so general as in Scotland. There are, however, great drift fisheries on the eastern and southern coasts of England, and an important mackerel fishery mainly at the western end of the channel, though owing to a high import duty on mackerel levied by France this is now of far less importance. The value of the mode of fishing technically known as " drifting or driving" will be understood when it is remembered that it is the only method by which such fishes as herrings, mackerel and pilchards, which generally swim at or near the surface, can be readily caught in the open sea, at any distance from land, and in any depth of water, so long as there is sufficient for the floating of the nets in the proper position. The term " drift-net is derived from the manner in which the nets are worked. They are neither fixed nor towed within any precise limits of water, but are cast out or " shot " at any distance from the land where there are signs of fish, and are allowed to drift in whichever direction the tide may happen to take them, until it is thought desirable to haul them in. The essential principle of the working of the drift-net is that it forms a long wall or barrier of netting hanging for a few fathoms perpendicularly in the water, but extending for a great length horizontally, and that the fish, meeting these nets and trying to pass them, become meshed; they force their heads and gill-covers through the meshes, but can go no farther; and as the gill-covers catch in the sides of the mesh, the fish are unable to withdraw and escape. Whether it be mackerel, herring or pilchard, the manner in which the. net works is the same; the variations which exist relate only to the differences in habits and size of the fish sought after.
The nets used are light cotton nets, each about 30 yards long and 10 or 12 deep, and when designed for herring have a mesh of about an inch square, pilchard nets being smaller and mackerel nets larger in mesh. These nets are laced end to end in a long row, the whole row, called a " fleet " or " train " of nets being, in the case of the large herring boats, as much as 32 miles long. One of the long edges of the net is fastened to a rope corked at regular intervals, whose purpose is to keep that part uppermost. This edge is called the " back " of the net. The corks are, however, not sufficient to keep the whole net from sinking, and this is done by buoys called " bowls, " which are attached to the back rope at intervals. It is always a matter of uncertainty at what depth the fish may be found, and a deal of judgment is needed in deciding what length of rope should be used in attaching the buoys. In the herring fishery of the English east coast the British boats usually work in somewhat shallower water than the foreign drifters, and set their nets at about 4 fathoms from the surface, the foreigners, lying outside them, using deeper-set nets. It is found convenient to colour certain of the bowls distinctively to indicate their position in the " fleet. " Otherwise they are coloured to show ownership.
Drift-net fishing is with rare exceptions only carried on at night. The time for beginning is just before sunset, and the nets are then got into the water by the time it is dark. A likely place to fish is known (though there is much uncertainty in the matter) by signs recognizable only to the practised eye. An obvious one is the presence of many sea-birds, or of the fish themselves. But besides these the appearance and even the smell of the water furnishes a guide. In the case of the mackerel these signs have been shown by G. E. Bullen (Journ. Marine Biol. Assoc. viii. 269) to be due to the character of the microscopic organisms in the water, some of which furnish the food of the mackerel, others of which it avoids. If fish is believed to be present the vessel is sailed slowly before the wind and if possible across the tide; then the net is shot or thrown out over the vessel's quarter, the men being distributed at regular stations, some hauling up the net from below, others throwing it over and taking care that it falls so that the foot is clear of the corked back; others, again, looking after the warp which has to be paid out at the same time, and seeing that the seizings are made fast to it in their proper places. When it is all overboard, and about 15 or 20 fathoms of extra warp, called the " swing-rope, " given out, the vessel is brought rcund head to wind by the warp being carried to the bow; the sails are then taken in, the mast lowered, a small mizen set to keep the vessel with her head to the wind, and the regulation lights are hoisted to show that she is fishing. A few of the hands remain on deck to keep a look out, and the vessel and nets are left to drift wherever the wind and tide may take them. It is very rarely that there is an absolute calm at sea; and if there is the faintest breath of air stirring the fishing boat will of course feel it more than the buoys supporting the nets; she will consequently drift faster, and being at the end of the train, extend the whole fleet of nets. In rough weather, as the strain may be greater, more rope is used. The first net in the train is often hauled after an hour to enable the men to judge whether the position is a good one. When the whole are hauled, the nets are taken in and the fish shaken out in the same orderly way as in shooting, each man having his own proper duty.
The sailing drifter is fast disappearing, giving place to the steam drifter. These vessels, though costing far more (£2500 to x:3000 against £400 only) catch more fish, have a greater radius of action,. reach market more quickly and are independent of weather. It has been calculated that a thousand square feet of herring netting used by a steamer catch 432 cwt. of herring, while a sailing vessel catches 20 cwt. with the same area of netting; and the steamer-caught fish, being more quickly delivered, fetches a better price. It may be noted that of recent years herring have been caught at the bottom in considerable quantities by the trawl. The fishing of herring is thus increasing in variety of method, as well as in intensity. Such sailing boats as tend to remain are long shore boats, and such drifters as have been fitted with petrol motors.
Stationary nets, being of very small importance relatively to the preceding, must be dismissed more shortly.
They are of four main kinds, viz.: stake nets, stationary Y Nets. pound and kettle nets, stow and bag nets, trammel-. nets and hose nets.
Stake nets are usually set between tide-marks, or in shallow water, and, as their name implies, are kept up by stakes placed at intervals. They are generally set across the direction of the tide. They act as gill nets, and are chiefly used Stake Nets. in America. In some cases a conical bag instead of a flat net occupies the space between every two stakes, forming a series of simple bag nets. This form is used on the German shores of the North Sea.
In another modification the net is supported on the stakes, which is some 200 ft. long, does not act as a gill net but as a " leader, " and one of its ends passes through a narrow opening into a circular enclosure surrounded by a similar .
wall of staked netting. The bag net and fly net for the capture of the salmon are merely elaborated forms of this type. The pound is roofed by netting, in the fly net, and in the bag net, which is floated - not staked - floored also. It is wedge-shaped, narrowing gradually from the entrance end, and divided incompletely by oblique internal walls or valves of netting into side compartments.
The bag net just described is practically a floating stake net. A simpler form is used in the Elbe, consisting of a pyramidal net whose mouth is held open by its sides being attached to spars, weighted at one end and buoyed at the other.
This is the simplest form of stow net. The stow net is used in the Thames and Wash; it is specially designed for the capture of sprats, although many young herrings are sometimes caught, and it is worked most extensively at the entrance of the Thames. The stow net is a gigantic funnel-shaped bag having nearly a square mouth, 30 ft. from the upper to the lower side, and 21 ft. wide. It tapers for a length of about 90 ft. to a diameter of 5 or 6 ft., and further diminishes to about half that size for another 90 ft. to the end of the net. The whole net is therefore about 180 ft. or 60 yards long. The upper and lower sides of the square mouth are kept extended by two horizontal wooden spars called " balks," and the lower one is weighted so as to open the mouth of the net in a perpendicular direction when it is at work. The size of the meshes varies from 1* in. near the mouth to 2 in. towards the end, where, however, it is again slightly enlarged to allow for the greater pressure of the water at that part. The mode of working the net is very simple. Oyster smacks are commonly used in this fishery, although shrimping boats are also employed in it in the Thames. The smack takes up a position at the first of the tide where there are signs of fish, or in such parts of the estuary as are frequented by the sprats during that part of the season; she then anchors, and at the same moment the net is put overboard and so handled that it at once takes its proper position, which is under the vessel. It is kept there by a very simple arrangement. Four ropes leading, one from each end of the two balks, and therefore from the four corners of the mouth of the net, are united at some little distance in front, forming a double bridle, and a single mooring rope leads from this point of union to the vessel's anchor; so that the same anchor holds both the vessel and the net. The net is kept at any desired distance from the bottom by means of two ropes, one from each end of the upper balk to the corresponding side of the smack, where it is made fast. The open mouth of the net is thus kept suspended below the vessel, and the long mass of netting streams away astern with the tide. The strain of this immense bag-net by the force of the tide is often very great, but if the vessel drags her anchor, the net being made fast to the same mooring, both keep their relative positions. Here they remain for several hours till the tide slackens, the vessel's sails being all taken in and only one hand being left on deck to keep watch. The way in which the fish are caught hardly requires explanation. The sprats, swimming in immense shoals, are carried by the tide into the open mouth of the net and then on to the small end, where they are collected in enormous numbers; from this there is no escape, as the crowd is constantly increasing, and they cannot stem the strong tide setting into the net. The first thing to be done in taking in the net is to close the mouth, and this is effected by means of a chain leading from the bow of the vessel through an iron loop in the middle of the upper balk down to the centre of the lower one, and by heaving in this chain the two balks are brought together and ultimately hoisted out of the water under the vessel's bowsprit. The net is then brought alongside and overhauled till the end is reached, and this is hoisted on board. The rope by which it is
closed having been cast off, the sprats are then measured into the hold of the vessel by about three bushels at a time, until the net has been emptied. The quantity of sprats taken in this manner by many scores of fishing craft during the season, which lasts from November to February, is in some years simply enormous; the markets at Billingsgate and elsewhere are inundated with them, and at last in many years they can only be disposed of at a nominal price for manure; and in this way many hundreds of tons are got rid of. The stow boats do not generally take their fish on shore, but market boats come off to them and buy the fish out of the vessel's hold, and carry it away. The mode of working is the same in the Solent and the Wash as that we have described in the Thames and large quantities of sprats are landed by the Southampton boats.
" Whitebait," or young sprats, mixed with some young herring and other small fish, are caught in the Thames by a net which is practically nothing else but a very small stow net, and it is worked in essentially the same manner. An interesting form of stow net is used in the Channels of the Frisian Island, chiefly during the rush of the ebb-tide, for the capture of rays (principally Raja clavata, the Thornback) which are highly valued by the Dutch. It consists of a net shaped like an otter trawl, furnished with otter boards, which are attached to ropes passed to the ends of long booms which project from the sides of the vessel using the net, and also to the two anchors by which the former is anchored.
The remaining stationary nets to be mentioned partake of the nature of traps. The trammel net consists of three nets joined together at the top, bottom and sides. The whole system of nets hangs vertical, the head line being Nets. buoyed and the ground line weighted. The two outer nets are much smaller than the inner net, but of wide-meshed netting, whereas the inner net is of very small mesh. Consequently, a fish meeting an outer net passes through it, strikes the fine-meshed net and forces it before it through one of the meshes of the farther wide-meshed net; it is thus in a small pocket from which it cannot escape.
The hose net is a long cylindrical net from which trap-like pockets open. The main cavity is kept open by rigid rings. The hose nets are set between tide marks, at low water, so that the tide runs through them; and they are emptied at next low tide.
While unimportant compared with the huge quantity of fish landed from sea-going vessels, the catch of the in-shore nets described is of importance in respect of the kinds of fish taken, whitebait and pilchards, for instance, being not otherwise obtained, while salmon, though taken in rivers as well as in estuaries and along the coast, is very rarely captured at sea.
Brabazon, The Deep-Sea and Coast Fisheries of Ireland (1848); Holdsworth, Deep-Sea Fishing and Fishing Boats (London, 1874); Z. L. Tanner, Bulletin United States Fishery Commission (1896), vol. xvi.; Garstang, ibid., vol. vi.; Kyle, Journal of the Marine Biological Association of the United Kingdom, new series, vol. vi. (London); Cunningham, ibid., vol. iv.; Petersen, Report of the Danish Biological Association, vol. viii. (Copenhagen, 1899); Hjort, Report on Norwegian Fishery and Marine Investigation, vol. i. (Christiania, 1900); Mittheilungen; Deutscher SeefischerVerein, various numbers; Fulton, Reports of the Scottish Fishery Board, 19th Report (1900); and in other numbers; Report and Minutes of Evidence of the Committee, " appointed to inquire into the scientific and statistical investigations now being carried on in relation to the fishing industry of the United Kingdom." (London, 1908). (J. O. B.)
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Chisholm, Hugh, General Editor. Entry for 'Seining and Netting Trawling'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/s/seining-and-netting-trawling.html. 1910.