284 Roosevelt Wild Life Bulletin 



result from the natural process. So by planting fry on the natural 

 spawning places, or older fish in their natural habitats, the only gain 

 attainable lies in the greater number planted than would have 

 hatched naturally from the same number of eggs deposited by the 

 parent fish in the spawning places, or in the case of older fish 

 would have resulted naturally from that number of naturally 

 produced fry. 



As elsewhere suggested, the question here arises, are the spawning 

 places capable of supporting more fry than would hatch naturally? 

 They are, of course, other things being equal, if the natural supply 

 of parent fish has been reduced. In this case the question con- 

 cerning the extent of reduction arises ; also the number of fry to 

 supply the deficiency. The same reasoning may be applied to 

 fingerlings, yearlings, etc., in their respective habitats. To exceed 

 those numbers in the final production of adult fish, might result in 

 disturbances of natural conditions that would give rise to worse con- 

 ditions than those which the artificial planting is intended to correct. 



When to Plant. The season of the year when young fish should 

 best be planted has been a much discussed subject, and there has 

 been more or less diversity of practice. The season would seem to 

 depend to some extent upon the kind of fish. However, the natural 

 habitat of the fish at the age to be planted being known, it would 

 appear to be a logical procedure to plant the fish approximately 

 at the time they are known to appear naturally in those places. How- 

 ever, the differences in time of hatching and rate of growth of 

 hatchery-raised fish may be a matter to be considered in this 

 connection. 



While, as has been stated, there are many facts and factors to be 

 considered in selecting the places in which young fish are to be 

 planted, there is one of prime importance, and that is the food 

 supply for the young fish. 



Food Supply. In the words of a former United States Commis- 

 sioner of Fish and Fisheries (H. M. Smith, '16), "our knowledge 

 of the food of fishes is as yet seriously inadequate. The food taken 

 by fishes varies with the species, with size and age of the fish, with 

 the season of the year, and with the abundance of the various kinds 

 of food material present in different bodies of water. A few ob- 

 servations in one locality or at one season of the year afford no 

 criterion for the conclusions that we may seek to draw, for an 

 appraisal of the possibilities of fish production in a body of water, 

 for an understanding of the variations in the sizes attained by a 

 given species of fish in different bodies of water, and for the direc- 

 tion of our efforts to promote an abundant and reasonably constant 

 supply of food under all conditions subject to control." 



Other things being equal, the statement is likewise true that 

 " barring enemies and artificial hindrances to increase, such as over- 

 fishing, fish will multiply up to the limit of the food supply, but 

 cannot overstep that limit. If the food supply can be increased, 

 an increase in the number of fish will naturally follow." (Pieters, 

 '01, p. 59.) 



