Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/257

TRAWLING.] FISHERIES 247 now have the long beam supported at each end by a more or less stirrup -shaped iron fitted at right angles. The next e net. thing to be considered is the net. This was previously spoken of as flattened and purse-shaped. When the net is spread out in the manner it would be when working, the upper part or back has its straight front edge fastened to the beam, but the corresponding lower part or belly is cut away in such a manner that the front margin forms a deep curve extending from the shoe of one trawl-head to 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 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 ground-rope 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 back of the net, and as the outlet under the beam is a long way past them, and is steadily moving on, their fate is sooner or later decided by their passing over the ground-rope and finding their way into the funnel- shaped end of the net", from which a small valve of netting prevents their return. The ground-rope is the part which directly bears 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 pro bably 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 feet, which part is called the " cod or purse," and is closed by a draw-rope or " cod-line " at the extremity when the net is being used. This 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. >ckets. We must now say a few words about the ingenious con trivances for preventing the escape of the fish which have entered the purse and reached the farthest extremity of the net. 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 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 feet 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 extremity. These pockets are not separate parts of the trawl, but are made by merely lacing together tho back and belly of the net, beginning close to the margin or side nearly on a level with the bosom, and then carried on with slowly increasing breadth downwards 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 under stand 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 further end of it. The water, however, which has expanded the body of the net, then passes through the flapper or valve, and enters the purse, which, being made 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 meshes of an ordinary deep-sea trawl vary in size Meshes, in different parts of the net, diminishing from 4 inches square near the mouth to 1| inches in the cod or purse. The under part of the net, being exposed to more wear and chafing than the upper, is usually made with rather stouter twine ; and the purse, being especially liable to injiiry from being dragged over the ground with a weight of fish and perhaps stones in it, has some protection provided by layers of old netting called " rubbing pieces " laced to its under surface. The French fishermen fre quently fasten a stout hide to this part of their trawls with the same object. A deep-sea trawl, such as has now been described, is therefore an immense bag-net, the largest size being about 50 feet wide at the mouth and about 100 feet long. Many of these nets are much smaller, some of them not having the beam more than 36 feet or even less, and the net reduced in proportion ; but there has been a great increase in the size of the trawl-vessels in recent years, and at the same time there has been an enlargement of the nets, although not quite in the same ratio. The trawl is towed over the ground by the trawl-warp, generally a 6-inch rope 150 fathoms long, and made up of two lengths of 75 fathoms each spliced together ; one end of this warp is shackled to two other pieces each 15 fathoms long, and called the " spans or bridles," which lead one to each end of the beam, and are shackled to swivel-bolts in front of the iron heads so as to give a fair pull on the whole apparatus. The great development of the trawl fishery in recent Size of years has led to a vast improvement in the kind of fishing trawl vessels employed in it. Fifty years ago the only deep-sea vesi trawlers were in the west of England, and from Barking on the Thames. They were not nearly the tonnage of many of the vessels now used in the North Sea, but were stout, heavy, seagoing craft of their size, and capable of standing almost any description of weather ; and, although comfortable, they were certainly not very fast. At that