[3] THE FIRST FOOD OF THE COMMON WHITEFISH. 778 



with what has been said above, it may not be difficult to overdo the 

 work of iiropagation. 



If the whitefish were to be multiplied indefinitely, without any atten- 

 tion to the character or abundance of its food supply, it would soon 

 reach such a number that it must infringe upon its own food capital, 

 diminish the average number of the animals upon which it depends for 

 subsistence, and so finally indirectly cripple itself. Then the money 

 and labor expended in its culture would be principally lost, and the last 

 state of the species would be worse than the first. An acquaintance 

 with the food of the young is especially necessary, because they are 

 planted by the fish-culturist when, having already absorbed the egg-sack 

 (the supply of food by which they are under natural conditions sup- 

 ported until they have time to scatter themselves widely through the 

 water), they are in a peculiarly helpless condition, unable to wander far 

 in search of subsistence, and compelled to find food speedily or perish. 

 One would say, therefore, that their alimentary resources and habits 

 should be well and thoroughly known, that the range, period, and 

 abundance of the organisms upon which they feed should be carefully 

 determined, and that each locality where the young are deposited should 

 be closely searched for the purpose of ascertaining whether their food 

 species occur there at the time in sufficient quantity to prevent imme- 

 diate starvation. 



Previous studies of the food of young fishes of a variety of families, 

 reported in the third paper of this series, had shown that, with excep- 

 tions presently to be mentioned, the earliest food of all the families 

 studied consisted almost wholly of various species of Entomostraca and 

 some equally minute and delicate dipterous larvae. When that paper 

 was prepared, I had, however, no opportunity to study the food of the 

 young of any members of the family Salmonidoe, to which the white- 

 fish belongs, neither could I learn that any such studies had been made 

 by others ; and I could only infer the same fact with regard to this fam- 

 ily from the general character of the results obtained by the study of 

 the other groups. Even this inference, however, was rendered doubt- 

 ful by the discovery that the youngest individuals of two of the tooth- 

 less families (CatostomidsB and CyprinidsB) were not strictly dependent 

 upon the food elements above mentioned, but were likewise able to 

 draw upon much smaller organisms, namely, the minutest Protozoa 

 and unicellular Algae ; and as the adult whitefish is likewise destitute 

 of teeth, it was not by any means certain that their young would not 

 fall under the latter category. Upon looking up the literature of tbe 

 subject, I found that, although the food of the adult had been very well 

 made out in a general way,* only two items had been published respect- 

 ing the food of the young. In the report of the United States Fish 

 Commission for 1872-'73, an assistant commissioner, Mr. J. W. Milner, 

 made some experiments on young whitefish hatched artificially, sup- 



* Report of the Uuited States Fish Commission for 1872-73, pp. 44-40. 



