in length : the fore and aft length of the actual net is rather less than that of the head rope, and as has been said that of the ground rope greater: the cod-end is usually about 14-18 ft. Much research has been devoted to determining the actual spread of the net when towed : and it appears probable that a 90 ft. head line gives a spread of rather over 5o ft.
The operation of shooting is carried out fundamentally as in the beam-trawl—i.e., the trawl is brought at right angles to the ship by running out the fore warp sufficiently, before both warps are lowered. The fore warp is then drawn to the quarter of the vessel, where it is shackled with the after warp during towing. Towing takes place at varying speeds, round about 21 knots, or in herring trawling 31 knots. Hauls vary in duration with the abundance of the fish: a common duration, seldom exceeded, is 3 hours. When about to haul the fore warp is released from the aft and the ship steered in a curve to bring them both at right angles to the side and so clear of the pro pellers. The warps are then rapidly wound in, and the net and cod-end brought on board as in the beam-trawl. The trawler carries her fish iced to port.
The movable nets most resembling trawls are seines. This net consists essentially of a long strip of netting with a buoyed headline and a weighted ground rope. It is taken out in a boat to some distance from shore, paid out in a curve concave to the beach, and the lines attached to the net being brought ashore, the net is hauled to land. This simple seine is used for the capture of smelts and other small fish, but most seines have developed into more complex forms, usually by changes involving the formation of a bunt, or a true cod-end in the middle of the net: and several forms are worked completely away from shore. Thus the Danish plaice-seine is now worked by a small steamer or motor vessel. It is a net some 18o ft. long, with a 5o ft. cod end, and to each wing over a mile of warp is attached. One end of a warp is buoyed, and the ship moves in a great oval, paying out warp, net and second warp, and then returning to the buoy, when both warps and the net are hauled by special winding engines. The net gives excellent results with plaice or, properly modified, with haddock on clean level sand at moderate depths, but has hardly fulfilled expectations for general fishing far from land.
This net is the last development of the Danish seines. A simpler form is the eel drag-seine, which is worked from a boat in shallow water. It is somewhat smaller (14o ft. long) tapering at the wings and with a bag of 3o ft., the wings are attached to spars and drawn on board by warps. The drift eel-seine is an interesting development. It is similar but smaller, and drifts with the boat, the ends of the net being kept apart by a floating spar or, latterly, by small trawl boards. The bag is valved by a funnel of netting.
The Mediterranean filet de boeuf may be here included, as a net having affinities with both trawl and seine. It is worked between two boats, and has a very long cod-end.
are shot about a shoal of these fish by boats guided by the signals of watchers ("huers") on shore. They are shot in a nearly complete circle, which is then closed by a short "stop" net, when lines from the ends of the main net are taken ashore and the whole hauled to the shallows. The fish are then removed by a "tuck net," a small seine through whose lowest meshes a line is rove, so that by hauling this line the net changes from a wall of netting to a shallow basin. The main seine is about 200 fathoms long: as in the trawl, the meshes decrease in size towards the cod-end or purse.
much used in the United States and in Japan, is in principle a tuck-net. The mackerel or other shoal is surrounded by a long wall of netting whose ground-rope bears rings through which is rove the line which on hauling converts the circle into a saucer. The slack of the net is then taken up gradually until the area is small and the fish are reached. In Japan the fish are guided into the purse by a long line of net which acts as a leader.
The nets of most importance after the otter trawl are the drift-nets employed for the capture of herring, mackerel and other fish which pass much of their life near the surface of the sea. Although both herring and, in less degree mackerel are now trawled, the main fishery for these important fish is carried out by the drifters.