xi METHODS OF FISHING 281 



catch was by Japan (3-8 million), followed by U.S.S.R. (2-5), U.S.A. 

 (2-3), and Great Britain (i-i). 



By far the greater part of all fishing is in the sea. In Great Britain 

 the total catch in fresh water annually is reckoned at only 2,000 tons 

 and the entire stock at 8,000 tons. However, there are important 

 fishing industries in the American Great Lakes, the African lakes, and 

 in many parts of the world carp are raised on fish farms, the water 

 being manured to yield a good crop of the freshwater plants and 

 invertebrates on which the carp feed. The milk fish (Chanos chanos), 

 which feeds directly on algae, provides high yields in many tropical 

 and subtropical fish-ponds. 



Fishing in the sea is limited mainly by two considerations. First, 

 the labour is only really profitable when the fish population is dense. 

 Secondly, fish do not keep well unless they are treated in some special 

 way and they are therefore best caught near to their market. For these 

 reasons the big commercial fisheries are mostly in the relatively shal- 

 low waters of the continental shelf (down to 200 fathoms) and in the 

 northern hemisphere. However, by packing the fish in ice or cooling 

 by other means, the vessels are now able to go longer distances than 

 formerly. Japanese and American vessels now fish for tuna and salmon 

 in the open ocean. 



For catching purposes fish may be divided into those that swim 

 away from the bottom, the pelagic forms, such as herring or mackerel, 

 and the bottom-living or demersal fishes, such as the skates and rays, 

 flat-fishes and angler-fishes. For the first the gear employed is usually 

 drift-net. This is of narrow mesh and is shot and left overnight, drifting 

 vertically near the surface, often making a barrier two or three miles 

 in length. The fish, such as herrings, swim into them, and become 

 enmeshed, and are removed as the nets are hauled in. 



The success of such fishing with drift-nets depends on laying the 

 nets in the path of large shoals of fish and it is therefore practised 

 especially in regions where fish congregate seasonally. For instance, 

 in the North Sea between East Anglia and Holland the herring con- 

 gregate in the autumn; at certain times, for unknown reasons, all the 

 fish in the area begin to move, making 'the swim', and they are then 

 caught in great numbers. Herring are usually caught at slack water. 

 At the October full moon, slack water occurs just after dusk and just 

 before dawn and catches are higher then. Other drift-net fisheries 

 depend on intercepting the fish when rising to feed. Evidently these 

 methods demand a close knowledge of the habits and migrations of 

 the fish. The fishermen have learned to know when and where to 



