32 U. S. BUREAU OF FISHERIES 



In striking contrast with this, there was a total mortality of 16.7 per 

 cent and an increase in the average individual weight from 0.445 to 

 1.135 grams in the control lot. 



The feeding experiment at the Wytheville (Va.) station, mentioned 

 in the previous report, was discontinued on April 29, 1925. In this 

 experiment rainbow-trout fingerlings were divided into two lots of 

 2,000 each. One lot (the controls) was fed a straight heart diet, while 

 small quantities of cod-liver oil and dried brewer's yeast were added to 

 the beef heart fed to the other lot. Throughout the experiment there 

 was a marked contrast in the mortality of the two lots. The total 

 mortality from May 29, 1924, to April 29, 1925, in the lot fed a diet 

 containing oil and yeast was 44.1 per cent; while in the control lot, 

 which received only beef heart, the loss was 82.8 per cent. The high 

 mortality in both lots was, no doubt, due in part to the fact that the 

 fish were kept in ordinary hatchery troughs throughout the course 

 of the experiment and, in the case of the vitamin-fed lot, became 

 badly crowded before the experiment was terminated. Yet, in spite 

 of this fact, the mortality in this lot was much lower than among the 

 controls up to the very end of the experiment. This experiment is 

 especially significant because it was conducted under ordinary hatch- 

 ery conditions and continued for a much longer time than any other 

 of the feeding experiments. 



HOLDEN EXPERIMENT STATION 



During the past year arrangements were made to utilize the Holden, 

 Vt., substation for experimental work in cooperation with the divi- 

 sion of fish culture. Such an experimental station is badly needed, 

 as it will provide an opportunity to investigate various problems con- 

 nected with the artificial propagation of trout and other fishes, for 

 which purpose the Holden station is well adapted. The hatchery is 

 supplied with both brook and spring water, which can be mixed in 

 any proportion required. There is also ample room for the construc- 

 tion of ponds of various types, which will be of great value in exper- 

 imental work. 



Experiments were begun at the station during the spring of 1925, 

 but owing to lack of equipment it was possible to hold only a small 

 number of trout through the summer. For this and other reasons the 

 work during the summer was of a purely preliminary character. Sev- 

 eral ponds were constructed and others will be added as soon as funds 

 are available. A small laboratory has been fitted up at the station, 

 and with the increased f acilities available it will be possible during the 

 coming season to carry on extensive investigations in the nutrition and 

 diseases of trout. It is also planned to conduct systematic experiments 

 in selective breeding in the hope that it will be possible to produce 

 a more vigorous and hardier race of brook trout better adapted to 

 hatchery requirements. 



In addition to the work at the station, a series of field investigations 

 is contemplated primarily for the purpose of obtaining more definite 

 information regarding the results of artificial propagation and the pos- 

 sibility of increasing its efficiency. There are numerous native trout 

 streams in the vicinity of the station, which will afford an excellent 

 opportunity for investigations of this nature. 



