50 U. S. BUEEAU OF FISHERIES. 



FOOD. 



Beef or sheep heart ground or chopped to a pulp seems to be the 

 most satisfactory artificial food for young trout. Second to this in 

 value is sheep liver, which is drier and more granular than beef 

 liver, and it can be used to good advantage for the first two or 

 three months or until the fish are large enough to thrive on a mixed 

 diet. European fisli-culturists have achieved at least loartial suc- 

 cess in producing a natural or living food, such as insect larvae 

 and small crustaceans, for artifically reared trout,^*' but nothing 

 better than the meats mentioned has been found. 



The proper method of feeding young fry should be understood 

 thoroughly, as the losses resulting from improper feeding are fre- 

 quently great. If there is undue haste, the water becomes polluted or 

 the food is so distributed that some fish do not receive their share. 

 Polluted water is very injurious to the young fish, sometimes causing 

 inflammation of the gills and other ailments, which often result in 

 heavy mortality. It may also produce, undersized fish. 



The fry are ready to take food as soon as the sac is absorbed, the 

 time required for this depending upon the rate of growth, which is 

 governed by the temperature of the water. In a uniform temperature 

 of 53° they will take food in about 30 days after hatching, and the 

 time to begin feeding may be closely estimated by observing the 

 movements of the fish. 



It is preferable to feed artificially reared rainbow trout on meat 

 entirely if it is plentiful and cheap ; otherwise a combination of liver 

 and mush will give satisfaction. The mush is made by stirring 

 wheat shorts or middlings in boiling water and cooking it until the 

 mixture becomes thick. After the mush is thoroughly cool the finely 

 ground heart or liver is added, the proportion usually being 20 

 to 25 per cent mush to 75 or 80 per cent meat. In some localities rye 

 shorts are obtainable in better grades than wheat shorts and at a 

 lower price, and the rye seems to be quite satisfactory as food for the 

 young fish. Enough of the mush for several feedings may be made at 

 one time, as it keeps well in a cool place, but the meat should not be 

 added at one time, but only as needed. 



Before the sac is entirely absorbed the school of fry at the bot- 

 tom of the trough will begin to break up and scatter through the 

 water, rising higher from the bottom each day until they can bal- 

 ance themselves gracefully in a horizontal position, all of them 

 heading against the current and swimming well up in the water. 

 By dropping small bits of cork or prepared food on the surface 

 of the water it can be determined if they are ready for food. If 

 they strike at the pieces as the current carries them down, it is evident 

 that they are hungry. 



The food is prepared by chopping it very fine and mixing it with 

 water, in order that it may be distributed evenly. It should be 

 given to the fish by dipping a feather into the food and gently 



10 Fresh-water Crustacea as Food for Young Fishes. By William C. Kendall. Appen- 

 dix I, Report U. S. Commissioner of Fisheries, 1922. Bureau of Fisheries Document No. 

 914, 1921, 



