ECONOMICS OF THE FISHERIES 313 



eat each other's eggs, they eat each other's young, they eat their own young, 

 they eat one another. As each animal grows to larger size in most cases its diet 

 changes accordingly, and itself becomes diet for different animals according 

 to their sizes. Relative size determines, in many cases, which is consumer and 

 which consumed. 



Of the five species, cod, haddock, rosefish, pollock, and whiting, which 

 together constitute more than half (58 per cent in 1945) of the total 

 fishery of the New England States, fishery biologists say of each, in effect, 

 that a catalogue of its direct food would include practically the entire fauna 

 of the region, and each of the five includes the other four as well as the 

 young of its own kind, in its diet.^^ 



A striking example of the way of life of fishes is given by Peck (1896): 



The food of the squeteague^- {Cynoscion regale [regalis]) may be charac- 

 terized perhaps most clearly by a concrete instance. On the morning of July 23 

 there was taken a large specimen whose stomach contained an adult herring, in 

 the stomach of the herring were found two young scup (besides many small 

 Crustacea), and in the stomach of one of these young scup were found copepods, 

 while in the alimentary tract of these last one could identify one or two of the 

 diatoms and an infusorian test among the mass of triturated material which 

 formed its food. This is an instance of the universal rule of this kind of food ; 

 the squeteague captures the butter-fish or squid, which in turn have fed on 

 young fish, which in their turn have fed upon the more minute Crustacea, which 

 finally utilize a microscopic food supply. And the food of the squeteague must 

 be regarded as a complex of all these factors, a resultant of several life-histories 

 to the given environment. Moreover, circumstances arising to modify any of 

 the separate factors cause correlative changes throughout the whole series. 



Contemplation of this internecine web of life should reveal the wide- 

 spread fallacy in the prevalent thinking about fisheries that each species 

 of fish can be singled out and protected, cultivated, conserved, or exploited 

 and marketed, and treated as an economic and biological unit as if it 

 stood alone and apart on its own nutritional foundation. It seems obvious 

 that this can be true to only a slight extent, and for a few such specific 

 feeders as the oyster. The catching of competitive finfish of one species 

 removes some of the competition for other species and for other individuals 

 of the same species which remain; and also some of itself as food for other 

 species. The totality of all kinds of fish in a water community should and 

 apparently does tend to be a constant in accordance with a Malthusian law 

 of subsistence, or perhaps to vary with the over-all production of basic 

 vegetable food in the region which might be affected by changes of tem- 



11. See, Bigelow and Welsh (1925), feeding habits under the headings of the above named and 

 other species. 



12. The gray trout of North Carohna. 



