94 REPOET OF COMMISSIONER OF FISH AND FISHERIES. 



the deep pools and eddies where it can lie concealed beneath the shelter 

 of grassy banks or logs, and see without being seen. Under artificial 

 conditions it endures higher temperature than in its native waters, 

 where it is seldom found in water warmer than 00° to 05°. It thrives 

 at much higher temperature in swift, well-aerated streams tban in 

 sluggisli waters. 



The broolv trout si)awns in autumn during the falling of the water 

 temperature. The season, which usually lasts about two monllis, begins 

 earlier in northern latitudes, in the Lake Superior region in September 

 or even August, while in New York, Kew England, and lower Michigan 

 it commences about the middle of October. 



As the spawning time approaches the fish push up toward the 

 shallower waters where the female selects a spot near the bank of the 

 stream and prepares her nest by washing out the sand with her tail 

 and pushing aside the gravel with her nose. After forming a slightly 

 concave depression she deposits a part of her eggs on the newly cleansed 

 gravel, and the male — which up to this time has been playfully swim- 

 ming around the nest — emits milt upon them almost simultaneously. 

 The female then covers the eggs with the loose gravel. The spawning, 

 impregnating, and covering are repeated continuously until the eggs 

 are all laid. After the spawning-ground is once selected it is hard to 

 drive the fish away, the female especially returning to the same spot at 

 the earliest opj)ortunity. A female has been taken from her nest and 

 marked and then returned to the water a mile down the stream, and 

 the next morning was found on the same bed as though nothing had 

 happened. 



The eggs vary in size, but are usually one-sixth of an inch in 

 diameter. The number yielded by one fish depends on its size and age, 

 yearlings usually producing from 150 to 250, two-year-olds 350 to 500, 

 and older fish 500 to 1,500. The time necessary for developing the eggs 

 is dependent on the temperature of the water, varying from about 125 

 days in water at 37° F. to about 50 days in water at 50° F. 



TROUT-CULTURE IN AMERICA. 



The first attempt at artificial trout-culture in America was made in 

 Oliio in 1853 and marked success attended the efforts. Further satis- 

 factory trials were made in 1S55 and 1859 in Connecticut and New York, 

 and in 1861 a hiitchery was established in New York which became a 

 practical success in carrying on the work on a large scale. Somewhat 

 later the work was taken up by the State and United States govern- 

 ments and is now very extensively carried on in all parts of the United 

 States. 



The methods described in the following pages are those which have 

 been found advantageous at the Northville station, and are there pur- 

 sued. In addition to the eggs obtained from brood fish held in ponds 

 at the hatchery a field station for collecting eggs from Avild trout is 

 operated on the Au Sable Eiver. 



