THE AXGLER AXD HIXTSMAX 107 



fish produce from 500 to 2,500. At Manchester, Iowa, the 

 eggs hatch in from 30 to 35 days in a water temperature of 

 50 degrees F., and brook trout in from 35 to 40 days in a 

 temperature of 50 degrees F. 



. "As a rule, rainbow r -trout eggs measure from 225 to 

 250 per fluid ounce, being considerably larger than those 

 of the brook trout, which range from 325 to 600 per ounce. 



"Experience has shown that the fish hatched from a 

 single lot of eggs frequently show such a wide variation in 

 size that at the age of 1 year some individuals will be only 

 four inches long while others will run from 6 to 8 inches. 

 This seems to be an inherent condition and is not easily 

 overcome, but the tendency may be counteracted to a cer- 

 tain extent by sorting the fish as to size from time to time 

 and giving the smaller ones extra food and attention. 



"The spawning period of the rainbow trout is affected 

 by geographical location. In the eastern States this fish 

 reproduces between early November and January; in the 

 middle western sections of the United States its spawning 

 season begins late in December and lasts for about three 

 months; while in the Rocky Mountain region and farther 

 west it spawns during a period of about six weeks, com- 

 mencing in April. Under natural conditions the fish make 

 a kind of nest by throwing up a mound of gravel in the bed 

 of the stream when the current is swift. The eggs float 

 into the gravel mound and lie in its crevices until hatched. 

 The fry remain concealed in the gravel about a month, 

 until the yoke sac is absorbed; they then begin to swim and 

 search for food. 



"Bearing these facts in mind, the trout culturist should 

 imitate natural conditions in the arrangement of his pond, 

 providing a raceway with a swift current of water and a 

 gravel bottom and allowing the fish access to it, so that they 

 may deposit their eggs at the proper time of the year. The 

 inlet to the raceway should be at least 4 feet wide and 

 from 75 to 100 feet long, both dimensions to be increas- 



