show the information available on 

 fish nutrition. Although such a re- 

 view is not included here, it is sug- 

 gested that interested persons con- 

 sult the issues of The Progressive 

 Fish Culturist (Fish and Wildlife 

 Service publication available in 

 many libraries) for the past few 

 years. This periodical contains 

 much information of value to the 

 salmon and trout culturist. 



Experience and research indicate 

 that the various species of salmon, 

 and of trout, do not thrive upon the 

 same diet. In fact, a diet of appar- 

 ently the same components fed to a 

 species of fish at one hatchery may 

 not be adequate for the same species 

 at another hatchery. Basic diets 

 have been developed, but these 

 usually must be altered to meet the 

 reauirements at different hatcheries. 



In past years it was possible for 

 each hatchery to secure its fish food 

 locally. Beef, hog, and sheep 

 livers, spleen, lungs, tripe, and 

 other products not commonly used 

 by humans were readily and cheap- 

 ly available. In recent years the in- 

 creased consumption of liver by hu- 

 mans and the marketing of dog and 

 cat foods utilizing the other prod- 

 ucts have greatly reduced the sup- 

 ply and increased the costs. During 

 this same period the requirements 

 for salmon and trout fingerlings to 

 maintain fisheries increased tre- 

 mendously. The result has been a 

 search for substitute foods readily 

 available in quantity and at low 

 cost. Many waste products have 

 been tried, but only salmon vis- 

 cera — eggs, testes, and ovaries — are 

 available in large quantities, es- 

 pecially in Alaska . Salmon viscera, 



when combined with some fresh 

 meats, have proved nutritionally 

 equivalent to foods previously fed. 

 It is probable that salmon viscera 

 from Pacific Northwest canneries as 

 well as large quantities from Alaska 

 must be utilized, as the annual fish- 

 food requirement of Pacific-coast 

 salmon hatcheries alone is expected 

 to exceed 10 million i)()uiids within 

 a few years. 



A practical hatchery diet must be 

 made up of components available in 

 quantity at low cost and providing 

 the nutrients necessary to produce 

 desired growth with minimum mor- 

 talities. Whether raw or frozen, 

 the food must be fresh when re- 

 ceived and must be retained un- 

 spoiled until fed to the fish. Meat 

 or fish products that have been 

 frozen should not be permitted to 

 thaw until required for the fish, and 

 thawed products or diets should not 

 be refrozen. The materials to be 

 incorporated in the diet should be 

 such as will combine to be presented 

 to the fish in the most desirable con- 

 sistency and form. 



Dry animal meals have been used 

 extensively in both trout and 

 salmon diets. Unfortunate results 

 have attended some of these efforts, 

 but satisfactory results may be se- 

 cured by preparing the meal at low 

 temperatures and considering the 

 percentages to be included in the 

 diet, the water temperatures, and 

 the species to be fed. Good results 

 have been achieved at the Grand 

 Coulee stations of the Fish and 

 Wildlife Service, where Burrows 

 (19-19) determined that— 



the Leavenworth production diet more 

 closely fulfills the various requirements 



34 



