74 FISHFOOD 



practical purpose of catching daphnia in sufficient quantities to feed fish 

 the collector should hunt pools in which there is considerable animal or 

 vegetable decomposition in process. Such conditions are found to perfec- 

 tion in the pools on the ground where city refuse is dumped. When the 

 conditions are favorable the daphnia rise to the surface in such quantities 

 as to color the water, the usual color being a rusty red. The color varies 

 from this to olive and gray. Fish breeders like to see the daphnia as 

 bright a red as possible, although it is an open question as to whether 

 the red ones are better food. The same individuals will alternate in color, 

 probably due to a difference in food. Usually these crustaceans are not 

 so plentiful as to color the water, and we have to use our eyes more 

 closely to locate them. The collector should provide himself with a 

 cheesecloth net about 12 inches in diameter and 15 inches deep, fastened 

 on a pole or jointed handle not less than 6 feet long. If an examination 

 of the water does not at first reveal any daphnia, the net should be tried 

 anyhow, using a gentle stirring motion back and forth, to stir up the 

 bottom water. Daphnia have very peculiar habits, and one can never 

 tell from day to day just how they are to be found, so that the collector 

 will always have to depend somewhat on his own resources. If an ex- 

 amination of the net after dipping for a few minutes shows nothing, try 

 elsewhere. If a swarm has been located do not take too many into 

 the net at one time, as the weight of the top ones crushes those beneath. 

 A mass that would bulk about equivalent to a small orange should not 

 be exceeded. Reverse net into pail of water and repeat until the water 

 is thick with daphnia. In cool weather the pail may be carried in this 

 crowded condition for about an hour. If the day is hot, a piece of ice 

 should be added to the water— enough to keep temperature down until 

 home is reached. Newspaper wrapped about the can helps the ice to last 

 longer. As soon as home is reached, add fresh water to the pail and 

 transfer the daphnia to tubs or tanks kept for the purpose. Like fish, 

 the water they are in should have as much air surface as possible. Do 

 not try to keep too many in stock, as overcrowding suffocates a number 

 and these, in turn, decomposing, kill the living ones. The cooler they 

 are kept, the longer they will last. In hot weather they can be kept about 

 three days and in October about two weeks. 



In transferring from carrying pails to stock tanks it is well to first 

 pour in small portions to a white enamel basin, which enables one to 

 carefully go over the catch and remove any insect enemies. (See page 

 96.) If the daphnia are too thick to be readily examined, some water 

 should be added. A little care in keeping out the enemies at the start is 

 energy well invested. Most of the enemies and the dirt may be sifted 

 out (under water) by using a screen just large enough for the daphnia. 



