58 



CONCLUSION. 



I cannot attempt to discuss the practical bearing of the 

 mass of data here presented, or of the much greater number 

 which I have withheld, partly because the time is lacking, and 

 partly because I know too little of practical fish-culture ; and I 

 will merely call attention to a few illustrative points which have 

 occurred to me in writing. 



It would seem that the fact that all young fishes compete, 

 at first, for food must have important practical results tending 

 in various directions. It is probable that all fishes which are 

 not especially adapted to the food requirements of the more 

 valuable fishes are hurtful to them, because they limit the food 

 available for their young. It seems possible that even the food 

 species of the predaceous fishes may multiply to an extent 

 injurious to the latter, since both robber and prey compete 

 while young for the same elements of food. It would seem 

 entirely likely that large fishes, like the shovel-fish, which 

 destroy when adult immense quantities of the proper food of 

 the young, must be reckoned as injurious. 



Again, it is evident that the fishes most desirable as food 

 for other kinds are those whose own food is not eaten by 

 valuable species, but exists in practically inexhaustible supplies. 

 The gizzard shad and the mud-feeding minnows are examples 

 of this sort; while the red-horse and other cylindrical suck- 

 ers answer the purpose almost equally well, since no valuable 

 fishes feed upon mollusks (especially preferred by the suckers), 

 and these are among the most abundant animals in our 

 western streams. The fact that they have likewise adapted 

 themselves to civilization, so far at least as to relish distillery 

 slops, is, perhaps, an additional recommendation from this 

 point of view. 



The smaller catfishes, being practically omnivorous, are the 

 rivals of every other kind ; and being almost perfectly pro- 

 tected from capture by their stout, sharp, poisoned spines, they 

 contribute little to the food supply of other fishes. The com- 

 mon sunfishes are almost equally worthless and injurious from 

 this point of view. 



