86 THE FISHING INDUSTRY 



except possibly amongst such sedentary fish as soles 

 and plaice. It must be remembered that trawling 

 is only commercially possible on comparatively smooth 

 ground and down to depths of about 200 fathoms. 

 Probably, therefore, the actual area trawled is only a small 

 proportion of the total area that is inhabited by fish. It 

 is possible, of course, that extensive and long continued 

 trawling in a confined and relatively isolated area may 

 scare the fish away ; it is probable, however, that any 

 area in which over-fishing appears to have produced 

 temporary exhaustion will tend to recover automatically, 

 since it would naturally be abandoned temporarily by 

 the trawlers for more profitable fishing grounds. There 

 is no doubt that trawling, unless the size of the mesh 

 is carefully controlled, tends to remove large numbers of 

 immature fish. Generally in ordinary beam trawling 

 cod, plaice, haddock, etc. the mesh varies from 3 ins. 

 diameter near the mouth of the net to about 1J ins. 

 diameter at the cod end. If a much smaller mesh were 

 used the resistance encountered by a full-sized net 

 would be so great that it would be almost impossible to 

 draw the net through the water. Smaller trawls of 

 | in. mesh are used in shallow coastal waters for catch- 

 ing shrimps, small plaice and whiting. The size of mesh 

 largely determines the size of fish that will be retained 

 by the net, since the smaller, immature fish readily escape 

 through the meshes. Of recent years the various 

 fishery boards, with a view to preventing the catching 

 of such small, immature fish, have increased the size 

 of mesh that is to be used particularly when trawling 

 within the three mile limit, where the greatest proportion 

 of immature fish is generally encountered. For steam 

 trawlers working in deep water a 2| in. mesh is generally 

 used, but within the three mile limit it is frequently 

 increased from 3 to 3| ins. 



