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The diagram at bottom shows the "purse 

 seine" net method of fishing. As it moves 

 in a circular path the boat unwinds a long 

 net until the circle is closed. While the 

 rim of the net is kept on the surface by 

 floats, the bottom part is allowed to sink. 

 Fish within the net are trapped when a 

 "purse string" line draws the bottom of the 

 net closed. This method is commonly used 

 in North American waters. A different method, 

 the "madi valai," is common along the Madras 

 coast of India. Four boats hold a net 

 suspended horizontally below the surface. 

 A long line with masses of weed Is then 

 lowered above the net, and when enough fish 

 have been attracted by the weed the net is 

 guickly drawn to the surface. 



This behavior of the herring was confirmed when marine bio- 

 logists discovered that local populations of herring differ from one 

 another in their average number of vertebrae, their rate of growth, 

 and age of sexual maturation. If there were widespread migrations, 

 interbreeding would result in a mixture of such characteristics. The 

 fact that there are local races seems to prove that the only migration 

 of a given local population is a limited one from deep waters to 

 coastal waters and back again. A similar story can be told of the 

 cod: Because local races have recognizable characteristics, the ex- 

 pert can take a particular specimen of cod and say which part of the 

 world it came from. 



A better understanding of the breeding and migration habits of 

 fishes means a better life for mankind. From the earliest times fish 

 must have been a staple article of men's diet. Through the ages we 

 have been concerned with devising easier and more efficient fishing 

 methods. Primitive man probably caught fishes by hand, flipping 

 them out of the water as bears and other mammals do. Later they 

 were speared or trapped in simple wicker baskets, the forerunners 

 of the cages and fish weirs still in use in many places. In the Japanese 

 province of Gifu cormorant fishing survives to this day. Torches 

 from the fisherman's boat attract the fish at night, then the birds, 

 which are on leashes held by the fisherman, are allowed to go 

 after the fish. A ring around the bird's throat prevents it from 

 swallowing its catch. In due course, the hook and line and the net 

 came to be invented; and today we have electric fishing and the 

 detection of shoals by radar or by echo sounder. 



Fishes, fishing, and fisheries have been closely linked with the 

 advances in civilization. Bjornson has put forward the view that 

 wherever a shoal of herring has touched the coast of Norway, there 

 the villages have sprung up. The siting of villages and towns, in 

 relation to the mass movement of herrings, can be seen also in 

 Scotland and eastern England, in Newfoundland, Alaska, Japan, 

 and Siberia. The wealth of the merchants of the Hanseatic towns of 

 Liibeck, Bremen, and Hamburg was founded largely on revenues 



