MANUAL OF FISH-CULTURE. 



183 



The fisli is so abundant, however, and the su])ply so well maintained 

 that fish-cultural work in its behalf is not now generally required. 



This fish spawns in late winter and early spring in the fresh waters 

 of the coast rivers and in the Great Lakes. In the Potomac River 

 spawning- takes place in February, March, and April. The water tem- 

 perature at which spawning begins is about 44° F., while 49° seems to 

 mark the maximum limit. This narrow range of temperature which 

 bounds the spawning act is somewhat noteworthy. 



Ovary of a yellow perch with nearly-ripe eggs, the forked 

 extremity beiug the anterior part of the roe. 



The eggs of the yellow perch are among the most remarkable that have 

 been artificially hatched. The spawn is in one piece, a much elongated 

 ribbon-like structure, of a semitrausparent light-grayish color. One 

 end of the large egg mass, corresponding to the anterior part of the roe, 

 is larger than the other, and is bluntly forked. The string is very long, 



Part of a receutly-laid mass of yellow-perch eggs. 



but may be much compressed lengthwise by virtue of its arrangement 

 in regular transverse folds like the sides of a bellows or accordeon. 

 When deposited the eggs are in a loose globular form, and after being 

 fertilized and becoming "water-hard" their mass rapidly becomes many 

 times larger than the fish which laid them. The length of the strings 

 is from 2 to more than 7 feet, depending on the size of the fish. One 



