116 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



1 foot 2 inches wide. At intervals of 18 inches, cleats If inches high 

 are mortised across the bottom, and in the sides of the trough, at 

 the ends of the cleats, grooves are made to admit the placing of a fine- 

 meshed vertical screen, which can fit tightly to the partition at the 

 bottom. Everything is coated with asphaltnm paint. The trough has a 

 fall of one-fifth of an inch to the foot, the overflow being at the end 

 through a tin spout. Another trough may be set at the lower end of 

 the first, provided, as with hatching-troughs, a sufiicient fall is given for 

 aeration, 



A week or ten days before the disappearance of the yolk-sac, which 

 will be absorbed in five or six weeks, with water at a temperature of 40° 

 to 45°, the fry intended for rearing should be transferred to the troughs. 

 In a single trough of the size described, 15 gallons of spring water per 

 minute, with a temperature ranging from 45° to 50° ¥., will support 

 8,000 fry during the first few weeks they are held. Up to this time it is 

 not necessary to insert the vertical screens except at the head and out- 

 let, but as the fry increase in size they become restless, snapping at each 

 other and crowding together in a mass at the head of the trough, and 

 then it is necessary to thin them out and separate them by subdividing 

 the troughs, holding an equal number of the fry in each of the compart- 

 ments. The action of the fish determines when this should be done. 

 The use of warm water hastens the development of the fry, the same as 

 it does with the eggs. 



For the first four weeks the fry are fed four times per day on finely 

 cliopi)ed beef liver, ladled through a close screen to remove all lumps. 

 The liver is diluted with water and the mixture fed to the fry with a 

 feather. For some days they do not appear to take their food, but tlie 

 routine is continued, and as soon as the sac is entirely consumed they 

 commence feeding. No rule can be laid down prescribing a definite 

 amount of food, but the fry are fed till their appetites are api^eased and 

 every fish has obtained a morsel. Some days they display more hunger 

 than usual, a warm day especially increasing their appetites. After 

 they begin to feed well the liver may be given to them but three times a 

 day, more being thrown in at a time. 



The troughs uuist be cleaned out daily by turning on an additional 

 supply of water — not so much that the fish will be carried against the 

 screen — and the foul matter stirred up from the bottom witli a feather 

 and worked through the wires with a. small sponge. Twice a week the 

 sides and bottom are sponged off. 



Three months after being transferred to the feeding-troughs, trout 

 will take food well and be from 1 to 2 inches long. They are then ready 

 to go outside to the rearing-x)onds. These ponds are about 32 feet long- 

 by 5 feet wide, with from 10 to 20 inches of water, and have a minimum 

 water supply of 20 gallons per minute. The bottom is graveled and 

 the sides constructed of planks or cobblestones, and on the sides where 

 the sun strikes the warmest during the day a board shades the trout 



