were, for instance, nearly 200 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 £10,000 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-grounds—there 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. 1.—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
resembles that of a kite. A kite dragged through
still air, owing to the position of the point of attachment
The Otter Trawl. Principle
of Action.
of the string, takes up an oblique position, in
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 ring bolts, and to each ring a wire warp, by which the trawl is towed, is shackled. The ring bolts are about the same distance from the centre of the board, but the two chains attached to the after-ring bolts 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 centred 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. The net is fastened to eyes placed at the top and bottom of the after-end of the board, but not to any intermediate point. This is to allow the part of the water swirling Details of Structure. The Boards. 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 212 in. round, and when the trawl is inboard lie coiled up on the separate drums of a steam winch. As wire can be run off or wound in on either drum separately, the adjustment of the lengths is much simplified. InThe Warps. 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 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 The Net. 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
