Reproduction and Growth 167 



stirred into the mass. They are set aside for an hour to 

 harden, for the eggs when they first reach the water are 

 soft and slightly sticky. At the end of that time they can be 

 placed in the flowing current of the hatchery troughs, where 

 they remain until they hatch. The young can be put in the 

 waters to be stocked as soon as the yolk-sac is absorbed, or 

 they can be retained and fed until they reach any desired 

 size. 



Trout are particularly well suited to the artificial method 

 for two reasons. In the first place the eggs, while not set 

 free in the body cavity as has often been stated, are so loosely 

 held by a thin membrane that the trained human hand can 

 easily manipulate them along the troughlike duct and out 

 the abdominal opening. (Both membrane and duct are so 

 delicate that it is difficult to open a trout without destroying 

 them, and they are therefore rarely seen.) And in the second 

 place, the eggs are only very slightly adhesive even at first, 

 and soon after extrusion absorb water to such an extent that 

 they become hard and elastic. 



There are other game fish in which artificial spawning is 

 practically impossible. In such a highly desirable form as 

 the black bass, the eggs, smaller and held by a much tougher 

 membrane, are hard to "strip" from the fish. They are very 

 sticky, and adhere to whatever they first touch. The term 

 "artificial propagation" is almost a misnomer as applied to 

 them, for the third method is artificial only in that the fish 

 are confined in prepared ponds. Here the adults, either cap- 

 tured from the wild or raised for breeding purposes, are 

 kept in a ratio of about two females to one male, and here 

 they deposit, care for, and hatch out their eggs just as they 

 would in natural waters. Either the fry or the parents can 

 be moved to other ponds after hatching to prevent can- 

 nibalism, and if golden shiners or other small fish have been 

 allowed to spawn in the water at the same time their off- 



