American Fisheries Soeiety. 59 



species is an enemy of all others, oftimes of its own. The spawn- 

 ing grounds of every kind of fish are likewise the-feeding grounds 

 of others, the spawn itself constituting the food; and every kind 

 of the larger species is either a fish destroyer or spawn destroyer, 

 or both, at some stage of life. 



Of course, this preying of one form of animal life upon an- 

 other begins much lower down the scale: in fact, the abundance 

 or scarcity of the highest forms, or ultimate product, is determined 

 by the volume of the lowest or fundamental forms. But the 

 building up process finally results in populating the waters with 

 a variety of animals suitable in size, form and texture as food for 

 man. These animals embrace many species, some of which are 

 prized far more highly than others, but all are alike without value 

 to mankind until caught, and the importance of any water as a 

 source of food supply depends, not on the number of animals 

 inhabiting it, but on the annual output of adults of the more 

 highly prized species. 



Opinions will vary as to the number or proportion of adults 

 that may safely be removed each year, but no one will deny die 

 proposition that all of the adults of any species might be caught 

 out each year as fast as they come to full maturity, provided that 

 a sufficient number of young of the same species were re- 

 introduced each year to make the loss good. Through the me- 

 dium of artificial propagation, which protects the ova that nature 

 leaves unprotected, this compensation of young is entirely feasi- 

 ble with the shad, the salmon, trout, whitefish, pike-perch and 

 some other species, provided always that the catching and killing 

 of the young and immature fish is absolutely prevented. 



Where artificial propagation is thus able to supplant natural 

 propagation, thereby eliminating the latter from consideration, 

 it is much better to catch ofif the adults as fast as they mature, 

 and thus make way for succeeding crops or generations. When 

 fish have matured, it is time, so to speak, to realize on the invest- 

 ment. They should then be converted into food, either for some 

 other fish, or for man. If allowed to remain, they defeat the 

 very object for which they were created, namely, to be caught 

 and utilized. The food which they consume by remaining should 

 all be converted into increment by going to the young and grow- 

 ing fish, instead of being wasted on the adults merel\- to prolong 

 their lives. When a female fish has matured and yielded a crop 

 of ova to the saving process of artificial propagation, she has 

 accomplished more in the way of reproduction that she could 



