590 U. S. BUREAU OF FISHERIES 



has been shown to give the best growth of any meat ordinarily used 

 at hatcheries, it was fed to the control lots and was the only meat 

 used straight. 



It is interesting to find that the growth obtained with mixtures of 

 meat and suitable dry products has each year approached more 

 closely or even surpassed that obtained in the controls, and this year 

 all the diets, with three exceptions, gave a greater growth than beef 

 liver. The results show very clearly that there are now a number 

 of dry products which, when fed in combination with fresh meat, 

 are superior to a straight meat diet and cost considerably less. In 

 other words, by the use of dry products it is possible to produce 

 better fish for less money than can be produced on the standard 

 hatchery diets in common use. 



The outstanding feature of the feeding experiments for 1930 was 

 the excellent growth and high color secured with dry salmon eggs. 

 For this reason it was planned to give the salmon-egg meal a thor- 

 ough test in the 1931 experiments and eight rations were made up 

 with the meal incorporated in various proportions. In general the 

 results of these experiments fully confirmed the conclusion reached 

 in 1930 — that in proper combinations salmon-egg meal makes the 

 best trout food now available. As is to be expected, the best results 

 were obtained with a mixture of salmon-egg meal and beef liver. 

 The meal was used at 30 and 50 per cent levels, but the results show 

 that 50 per cent of salmon eggs is too high for small fingerlings, 

 although it can be safely used after the fish reach a length of 3 to 4 

 inches. With small fingerlings a considerable percentage of the 

 meal is uneaten if more tlian 30 per cent is used in the mixture. In 

 general the smaller the fish the greater the difficulty in feeding dry 

 products, and in ordinary hatchery practice there is probably little 

 to be gained in attempting to feed such products before the young 

 trout are about 2 inches long. 



The fish fed a mixture of sheep liver and salmon eggs made a 

 slightly greater growth than those on beef liver mixture, but the 

 mortality was higher. Data secured in previous experiments indi- 

 cate that sheep liver is inferior to beef liver for brook trout when 

 fed straight, but that in combination with certain dry products it 

 gives much better results than when fed alone. Pig liver when used 

 with salmon eggs was somewhat inferior to either beef or sheep 

 liver, but owing to its lower cost it may be found advisable toi use it 

 with the larger fingerlings. For some reason a mixture of pork 

 melts and salmon eggs proved a complete failure — the fish refuse to 

 eat it and suffered such a heavy loss that the lot was discontinued 

 early in July. 



The superiority of salmon eggs rests not only on its ability to 

 produce rapid growth but also on the fact that fish reared on this 

 product show exceptional vigor and remarkably brilliant coloration. 

 As might be expected, the latter is more marked in yearling than 

 in fingerling fish, but is very noticeable at any age. It has also been 

 found that an equally marked improvement in the color of rainbow 

 and black-spotted trout follows the use of salmon eggs. This was 

 especially noticeable in a lot of yearling rainbows, which showed a 

 remarkable development of red and orange hues before the end of 

 the summer. 



