UNUTILIZED FISHES AND THEIR RELATION TO THE FISHING 



INDUSTRIES* 



By Irving A. Field. 



INTRODUCTION. 



The destruction of food fishes by fishes of little or no commercial 

 value is a subject of obvious importance to the fishing industries. 

 To preserve for his own uses the species he values, it becomes neces- 

 sary for man to control the depredations of his rivals. 



Under normal conditions the balance among the different forms of 

 life is maintained by natural laws. Where great destructive forces 

 are at work upon a species that species will be found to be endowed 

 with great powers of reproduction. The lobster, for example, wholly 

 defenseless in its early stages, and even when mature the prey of a 

 host of enemies, is able to perpetuate itself because of its enormous 

 fecundity, there being a biennial production of about 15,000 eggs by 

 each mature female lobster. The smooth dogfish, on the other hand, 

 a most destructive enemy of the lobster but itself comparatively free 

 from enemies, produces from four to a dozen young at a time, and 

 these are practically adult in form at birth. 



The natural balance, however, is seriously disturbed by man, for 

 whose purposes the supply of one species is exhaustively drawn upon, 

 while another, perhaps destructive, form undergoes no diminution. 

 To offset the drain upon the valuable species, close seasons have 

 been created to afford them protection during the breeding periods, 

 fish hatcheries have been established to replenish their numbers, and 

 sometimes the destruction of their natural enemies has been sought 

 by means of bounties or through the introduction of parasites. Effect- 

 ive methods of lessening the destructiveness of the useless marauders, 

 however, are the important factor lacking in present conditions. 

 While the struggle for existence has grown constantly more severe 

 for the lobster, which has man as a new enemy, the smooth dogfish 

 has continued unmolested, and thus increased in numbers. And 

 so with the other commercial species and their nonvalued enemies. 

 With the fish culturist's aid and the legislator's care a species may 

 be able to maintain itself even against the combined agencies of its 

 natural enemies and man; but the struggle is increasingly difficult, 

 and it is ultimately hopeless in some cases. The possible advantage 



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