MANUA.L OF FISH-CULTURE. 61 



more eagerly devoured, and ai^pareutly no other food has contributed 

 more to the growth of the fish; but the time expended iu collecting is 

 out of all proportion to the quantity of food secured. Perhaps a series 

 of breeding-tanks arranged in proximity to the fish-troughs, into which 

 the water containing the larvte might be drawn when desirable by the 

 simple opening of a faucet, would reduce the labor involved. 



Middlings and flour have been tried in combination with blood from 

 the shambles, but did not appear to satisfy the fish so well as the vari- 

 ous forms of meat, aiid their use has, therefore, not been continued. 

 They were fed in the form of a pudding composed of two parts blood 

 and one part flour or middlings, cooked carefully to avoid burning, 

 and the mixture was then passed through a meat-chopper and ladled 

 out with a spoon, like other chopped food. 



The growth of live food in the ponds themselves in which the fish are 

 maintained has been the subject of study. Ponds several years old 

 and Avell stocked with vegetation were at one time devoted to these 

 experiments. They had been empty during the preceding winter, and 

 in the spring were fertilized with various sorts of animal and vegetable 

 refuse. They were stocked with different species of Crustacea native 

 to the region, including shrimps {Gammarns) and entomostraca, of the 

 genera Daphnia, Ceriodaphnia^ Sida, Cyclops, Polyphemus, etc., which 

 were systematically collected from open waters by nets and other appa- 

 ratus and placed in the ponds. These forms all multiplied there, some 

 of them enormously, but no means was found of inducing continuous 

 or frequent reproduction of them, and the young fish soon exhausted 

 the supply. 



In serving the food the attendant carries it with the left hand — in a 

 2-quart dipper if chopiied meat, in a larger vessel if maggots — and, 

 dipping it out with a large spoon, strews it the whole length of the 

 trough, being careful to put the greater portion at the head, where the 

 fish nearly always congregate. Finely chopped food, for very young- 

 fish, is slightly thinned with water before feeding. 



It is usual to feed the meat raw except the lights, which chop better 

 if boiled first; but occasional lots of meat, on the point of becoming" 

 tainted, are boiled to save them. All meats fed directly to the fish are 

 first passed through a chopping-machine. To fish just beginning to 

 eat, food is given four times a day, or in some cases even six times, but 

 as the season progresses the number of rations is gradually reduced 

 to two daily. In winter such fish as are carried through are fed but 

 once a day. 



CLEANING THE TROUGHS. 



The troughs are all cleaned daily. When the hollow plug is drawn 

 the water rushes out rapidly and carries most of the debris against the 

 screen. The fishes are excited, and, scurrying about, loosen nearly all 

 the dirt from the bottom; what will not otherwise yield is started with 

 a brush, but after the first few weeks the brush has rarely to be used 



