ARTIFICIAL. PROPAGATION OF TROUT. 51 



skimming it over the surface of the water. After the fish have 

 grown to be 1^ to 1| inches long, they begin to take food that settles 

 on the bottom of the trough, and it may then be given with a spoon. 

 The young fry are fed five times a day, the food being given slowly 

 and sparingly. After they learn to take their food from the bottom 

 of the trough it is necessary to feed them only three times a day, 

 but the amount given at each meal must be increased. Fish that are 

 being fed artificially should not be carried in troughs that overflow 

 into other troughs containing eggs or newly hatched fry, as parti- 

 cles of food will pass through the screen and cause trouble. 



"VA^ien the fish are first fed, the meat is prepared very carefully. 

 The liver is usually " skinned " and all fat and connecting tissue 

 removed from the heart. It is then passed through the finest plate 

 of a meat chopper several times. These machines are provided with 

 plates having holes from one-twelfth to one-half inch in diameter, 

 so that the meat can be prepared fine or coarse, according to the size 

 of the fish to be fed. At the bureau's stations the Enterprise food 

 chopper No. 42, driven by a two or three horsepower gasoline en- 

 gine, is employed. 



The practice of throwing food into the pond by handfuls is en- 

 tirely wrong, as it causes the fish to rush together violently, with 

 open mouths, struggling to get a bite of food. They often hurt 

 each other and injure one another's eyes, sometimes even plucking 

 them from their sockets. This is probably one of the main causes of 

 blindness among pond-fed fish. 



The most approved method of feeding is to walk along the entire 

 length of the pond to the upper end and then scatter a handful of 

 food along the surface of the water so that it will fall to pieces. 

 The fish quickly learn to follow and take up the food and then re- 

 turn to watch for the next handful. The operation is repeated 

 until sufficient food has been given. This method of feeding induces 

 all the fish to head in the same direction while eating, thus reducing 

 the danger of injury. 



The proper amount of food for a given number of trout depends 

 upon their size, the temperature of the water, and to some extent 

 on the kinds of food used. More food is required when the water 

 temperature is comparatively high than when it is low. With water 

 from 50 to 60° F. and food consisting of meat and wheat or rye 

 mush, as described, the following daily ration for 1,000 fish will 

 be found to be approximately right : Fingerlings, 3 to 6 inches long, 

 2 to 3 pounds per day ; yearlings, 8 to 12 inches long, 4 to 8 pounds 

 per day ; adults, 8 pounds per day. 



As the fish increase in size the amount of food should be in- 

 creased proportionately and the number of feedings per day re- 

 duced until at the yearling stage they should receive food only in 

 the morning and evening at regular hours. Some fish-culturists 

 find one feeding per day satisfactory for year-old and older fish. 

 In the table below are indicated the kind and amount of food per 

 month per 1,000 rainbow trout of different sizes at some of the 

 bureau's stations. 



