102 FISHERIES OF THE NORTH SEA 



In their fight to eat and avoid being eaten 

 the battle of life would be too unequal ; 

 in such a contest the only hope the surface 

 fish would have would be to drag his deep- 

 water opponent up into surface depths, 

 when the absence of pressure would alone 

 kill it. 



The Canadians in their search for halibut 

 catch immense quantities of a species of 

 cod-fish. This fish, although not a true 

 cod-fish, is a fine food; but they have as 

 yet no demand for it, and it is thrown 

 overboard as soon as caught. Although 

 alive, these fish die on the surface; for, 

 having come out of the deep water, the 

 gases in their swim bladder, which at a 

 depth are compressed, expand and render 

 the fish lighter than the water. The 

 result is that they are imprisoned on the 

 surface and die. (This not only illustrates 

 the fact that shallow- and deep-water fish 

 keep to their own habitat, but also the 

 great wastage which goes on in some of the 

 fisheries.) 



One of the exceptions to this rule is the 

 eel, which annually descends to the deep 

 sea in autumn and winter to breed, and 



