132 U-S. BUREAU OF FISHERIES 



cases a somewhat smaller amount of food was required to produce 

 the same growth than with fingerlings, but this is probably caused by 

 the fact that there is less waste in feeding larger fish. For the same 

 reason larger amounts of dry foods can be included in the diets after 

 the fish reach a length of 4 to 5 inches. 



A number of experiments were undertaken at Leetown in coopera- 

 tion with the Birdseye Laboratories, Gloucester, Mass., in feeding dry 

 meals prepared by a special low-temperature process to rainbow trout 

 fingerlings with and without the addition of fresh meat. Two dry 

 meals were used in these experiments; one being composed of a mix- 

 ture of meat meal, fish meal, and dried skim milk; the other had a 

 similar composition except that it contained a considerable amount 

 of dried beef liver. Each of these meals was fed to 3 lots of fish for 

 over 8 months without the addition of any fresh meat or other food. 

 One lot was fed meal which had been prepared before the experiments 

 were started and stored in air. The second lot was fed meal which 

 had been stored in carbon dioxide, while the third lot received meal 

 prepared fresh each month and likewise stored in carbon dioxide. 

 The losses were not excessive in any lot, but were noticeably less in 

 those receiving meal stored in carbon dioxide. There was little dif- 

 ference in the mortality of the fish fed the meal stored in carbon 

 dioxide from the beginning of the experiment and those receiving 

 that prepared fresh each month. The growth of fish fed meal con- 

 taining dry beef liver was slightly less, but there was very little 

 difference in the mortality of the fish on the two meals. 



Two lots of fish fed dry haddock roe prepared by the same process 

 made a good growth with very little mortality. The growth on had- 

 dock roe was much superior to that obtained with the meals and the 

 fish showed an even more brilliant coloration than those on a salmon- 

 egg meal and liver diet. 



It is evident from these experiments that trout are able to live 

 indefinitely on dry foods when properly prepared. In no case, how- 

 ever, did the fish on an exclusively dry diet grow as rapidly as those 

 fed salmon and liver. The haddock roe was not fed in combination 

 with liver, but both of the meals produced a considerably greater 

 growth when mixed with 20 to 40 percent of beef liver. Even then, 

 however, the growth was inferior to that obtained with diets 

 containing salmon-egg meal. 



Selective breeding. — The work on selective breeding has been con- 

 tinued at Pittsford along the same lines as in previous years. So far 

 the work has been confined to brook trout, but the results have been 

 so encouraging that it is planned to expand it to include rainbow 

 and brown trout. Most of the breeding work with these two species 

 will be carried on at the Leetown station, where several thousand 

 brook, rainbow, and brown trout are now being reared to maturity. 

 During the fall of 1932 eggs were taken from 51 pairs of selected fish 

 at Pittsford and the young will be kept separate until next fall when 

 the inferior lots will be discarded. So far in these experiments spe- 

 cial attention has been paid to rapidity of growth, vigor, and fecun- 

 dity. The results attained have been remarkable considering the 

 short time the work has been carried on. 



Fingerlings reared in these experiments during the past summer 

 represent the third generation of selected fish and many lots made a 

 much greater growth than did the fingerlings from the general brood 



