FIELD BOOK OF PONDS AND STREAMS 



mingbird, and pearl organs appear on the head of the blunt- 

 nosed minnow (p. 336). 



During the breeding season the male and female usually 

 stay close together and the male discharges sperm cells over 

 the eggs the instant they are scattered into the water. Often 

 at this time both fishes take a very definite position. The 

 female rainbow darter half buries herself in the bottom gravel 

 and lays a few eggs at a time, the male shedding sperm cells 

 over them as soon as they appear. Many fishes build nests, 

 sometimes elaborate and constructed by both parents, some- 

 times only by the male, as in the brook stickleback (p. 339), 

 which fashions its nest and then swims forth to coerce a mate 

 into it. 



The eggs may be guarded and cared for, the male often 

 taking the greater if not the sole responsibility for them. 

 Among the yellow catfishes both parents keep the eggs clean 

 by stirring and fanning them with their fins; occasionally they 

 take a few into their mouths, then spit them out again, repeat- 

 ing the performance over and over. After hatching, they 

 tend the young fry even more thoroughly and turn them over 

 and about, using their barbels (Fig. 278) for stirring rods. 



Aquarium study. — Several of the fishes later mentioned live 

 well in aquaria, but whatever their kind, they must be small, 

 unless the aquarium is a very large one. A fish about one 

 inch long should be given a gallon of water, and water should 

 always be allowed in proportion to the size and number of 

 fishes. They should have plenty of water plants (p. 39) 

 about them and a small supply of food. Natural food is the 

 best for them, is healthier and far more interesting than pre- 

 pared fish foods. The best natural fish foods are small crus- 

 taceans like Daphnia and Cyclops, midge larvae, and other 

 small insects, especially the nymphs of quiet water mayflies. 



In selecting the fishes it is important to choose those which 

 will live peaceably together. Different kinds of minnows 

 will do this, but sunfishes, catfishes, and sticklebacks will not. 



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