580 FISHING NETS, WITH SPECIAL REFERENCE TO THE OTTER-TRAWL. 



is demanded by the smaller mesh would mean that the otter-boards 

 would not spread out satisfactorily, and the net consequently would not 

 fish well, if at all. On the other hand, if the meshes of the square are 

 open to their fullest extent, it is different with the meshes in the 

 winss. As a result of the " slack " at the sides, the meshes there will 

 be extended lengthwise and not so fully open as in the square. The 

 result is that the main rush of water down into the bag is along 

 the sides, and this should be the path the majority of the fish caught in 

 the net will travel. 



The greatest difficulty in the working of the otter-trawl is to ensure 

 that the head-line is well off the bottom. If it tends to sag in the 

 centre, the results of the fishing will show that for one thing, and 

 if it bends so far as to touch the ground the rope will be frayed or 

 have some dirt on it. If the mesh in the square were smaller the 

 force of the water when it passed under the head-line would tend to 

 raise the net, but the objections to the smaller mesh are twofold : 

 firstly, if the head-line sagged in any part the pressure of the water 

 would act on the net cibove the head-line and thus drive it down ; and 

 secondly, the smaller the mesh the greater the resistance to the water, 

 and the greater, therefore, the " wave " in front of the net. In neither 

 case would the fishing be a success. 



Various patents have from time to time appeared with the intention 

 of overcoming this difficulty. In Epton's patent two large air-bladders, 

 with coating of rubber and surrounded by netting, are fastened one 

 to each top-quarter. In another patent an air-bladder of similar 

 material, but tubular in shape and some 6 to 10 ft. long, is attached 

 to the net over the centre of the head-line. It is said by some, 

 however, that the resistance these ofter to the water is appreciable. 

 Tanner's idea,* which has been adopted by Petersen and Hjort, to 

 fix glass spheres enclosed in netting round the head-line, would hardly 

 do for professional fishermen. The most recent patent, and one which 

 seems most likely to be successful of any yet tried, is to attach two 

 small otter-boards to the top-quarters and to the main otter-boards 

 in such a way that they would tend to rise in the water, and therefore 

 pull up the head-line. 



Another difficulty lies in the choice of the right size of ground-rope 

 to use, though it has been more experienced by naturalists and sailing 

 trawlers than the steamers. In the sailing trawlers the wind may be 

 so light that the boat cannot pull the ground-rope over the bottom fast 

 enough, and mud or stones getting into the net may tear it to pieces. 

 Sometimes also, even with a good breeze, the trawl may come upon 

 a bank of sand or mud which reaches higher than the beam and means 

 * Bull. U.S. Fish Commission, xvi. 1896. 



