32 tr. S. BUREAU OF FISHERIES. 



for two or three weeks after the beginning of the feeding period. 

 As the fingerlings increase in size they must be thinned by removing 

 some of them, and by the time they have attained a length of 3 

 inches not more than 5,000 can be safely carried to a trough. 



For the first four weeks the fry are fed from four to six times a 

 day on finely chopped beef liver or beef heart. The food must be 

 carefully trimmed of all fat and gristle, and, after being run through 

 the finest plate of a meat chopper two or three times, it should 

 finally be passed through a tin having perforations one-tenth inch 

 in diameter. This tin is usually placed between the knives and the 

 plate on the meat grinder. Just before giving it to the fish the food 

 is diluted with water and carefully stirred with a spoon. A small 

 amount is then dipped up with a feather and carefully placed in 

 the troughs. For some days the fish will appear not to be taking 

 their food, but with the continuance of the feeding routine the entire 

 lot will soon commence to feed. No prescribed quantity of food can 

 be suggested for a given number of fish. The amount must depend 

 upon the manner in which the fish take it. From 50 to 70 days after 

 hatching the number of feedings per day may be reduced to three. 



The troughs must be thoroughly cleaned twice daily, morning and 

 evening, and during the cleaning process it is usually well to double 

 the flow of water. The foul matter in the trough may be gradually 

 worked to the foot screen with a feather, and by reducing the depth 

 of water in the trough the scurrying of the fish will hasten the flow of 

 sediment toward the foot screen. 



After the fish reach a length of 2 or 3 inches they may be dis- 

 tributed in outside rearing ponds. At stations of the bureau where 

 lake trout were formerly reared in ponds from 50,000 to 75,000 fish 

 of this size were held in a pond 100 feet long, 5 to 6 feet wide, and 

 provided with a flow of 35 to 50 gallons of water per minute, at a 

 temperature not exceeding 50° F. Ponds for work of this character 

 should have natural earth sides and gravel bottoms. 



o 



