192 • U. S. BUREAU OF FISHERIES 



the acre. This time the rate of survival was only 29.6 per cent and 

 the finti;erling production was lowered to 7,581 per acre. This 

 reduced yield is probably attributable to an invasion of crayfish. 

 When this pond was drained in the fall the bottom was literally 

 covered with these crustaceans and over 500 pounds were collected and 

 removed. Crayfish not only compete with the bass for food, but 

 they may also prey on them, to some extent at least. In former years 

 very few crayfish were found in this pond. 



The followinp; comparison of results obtained in 1928 at Fairport 

 and the bureau's station at Tupelo, Miss., may be of interest. At 

 Fairport a 3-acre pond was stocked with bass fry at the rate of 

 20,000 per acre. The fingerlino; production amounted to 6,487 per 

 acre, the percentage of survival being 33.4 per cent. At the Tupelo 

 station a 3-acre pond was stocked at the rate of 7,666 fry per acre 

 (Leach, 1930, p. 806). This pond produced fingerlings at the rate of 

 2.510 per acre with a percentage of survival of 30.6 per cent. The 

 diiference in the rate of survival is insignificant, but the fact that a 

 3-acre pond in one case produced 19,462 fingerlings for distribution 

 and in the other only 7,530 deserves some consideration. 



In the work at Fairport the number of fry in nursery ponds has 

 varied from 11.000 to 36,000 per acre.- Our highest percentage of 

 survival, 55.6 per cent, was obtained in a pond stocked at the rate of 

 14.000 fry per acre. A survival rate as low as 17.6 per cent has been 

 obtained\vhen stocking at 11,000 per acre. The maximum fingerling 

 production of 11.500 per acre with 46 per cent survival was obtained 

 in a pond stocked with 25,000 fry per acre. 



Considering the slight expense involved in the production of fry 

 and the much greater cost of producing fingerlings, we feel that 

 20,000 to 25,000 fry per acre is probably near the optimum stocking 

 intensity. In recommending this number we have in mind the pro- 

 duction of the maximum number of fingerlings per acre without 

 artificial feeding. It is our opinion, based on four years careful 

 observation, that the average rate of survival can not be expected to 

 go much above 40 per cent. In some years it may even fall con- 

 siderably below this figure. It seems that a certain number of fish 

 disappear between the fry and fingerling stages regardless of the 

 stocking intensity, although naturally the losses are greater when 

 large numbers of fry are used. We have at present under considera- 

 tion some experiments to determine the time and cause of this heavy 

 mortality. 



FORAGE FOR YOUNG BASS 



It is generally agreed that the young of black bass at first subsist 

 principally upon entomostraca and a little later, when about an inch 

 long, Ijegin to feed upon the smaller aquatic insects. As they in- 

 crease in size larger insects appear in the food, and shortly thereafter 

 the young bass begin to prey ui)on small fish. (Forbes, 1880 ; Pearse, 

 1918 and 1921 ; Turner andKraatz, 1920; Wickliff, 1920.) After the 

 fingerlings reach a length of about 2 inches they appear to subsist 

 largely upon fish, when these are available. This being the case, if 



2 This is Gxclusivo of the data for F 2 and F 3 for 1926. As these ponds were really 

 stocki'd with li'iigi'iiinys the ri'sults are not directly coiiipurablc 



