472 AMERICAN FISHES. 



which immures the Trout in their homes in the hill country as closely as 

 would a mountain wall. Difficult Run, a few miles above Washington, is 

 a natural Trout stream, and the species occurs in other streams near Balti- 

 more and Washington. 



When Trout have no access to the sea they still contrive to avoid a 

 change of temperature with the seasons. In midsummer they lie in the 

 bottoms of lakes cooled by springs, in the channels of streams, or in deep 

 pools, lurking behind rocks and among roots. In spring and early sum- 

 mer they feed industriously among the rapids. At the approach of cold 

 w^eather in autumn they hasten to the clear shallow water near the heads 

 of the streamlets. It is at this time that they deposit their eggs in little 

 nests in the gravel which the mother-fish have shaped with careful in- 

 dustry, fanning out the finer particles wath their tails, and carrying the 

 large ones in their mouths. After the eggs are laid, the parent fish covers 

 them with gravel, and proceeds to excavate another nest. The same nests 

 are said to be revisited by the schools year after year. 



The spawning season begins in New England in October, continuing 

 from three to six months, and during this period the fish should be pro- 

 tected by stringent laws. Mr. Livingston Stone observed that in his 

 ponds at Charlestown, N. H., spawning began October 12 and ended 

 early in December; at Seth Green's establishment, near Rochester, N. Y., 

 it began on the same day, and continued until March. At the former 

 station spring water, with a uniform temperature of 47°, was in use, 

 wdiile at Caledonia the eggs Avere kept in brook water, which is colder in 

 midwinter, retarding development. 



Trout eggs are usually three-sixteenths of an inch in diameter, although 

 varying greatly, and are colorless, red or orange-hued. The quantity 

 yielded by a fish is in direct proportion to its size, the average being from 

 four to six hundred. Mr. Stone took sixty from a half-ounce fish, and 

 eighteen hundred from one which weighed a pound. The eggs having 

 been laid, their time of development depends strictly on the temperature 

 of the Avater. According to Mr. Ainsworth, they will hatch in one hun- 

 dred and sixty-five days with the mercury at 37°, one hundred and three 

 at 41°, eighty-one at 44°, fifty-six at 48°, forty-seven at 50°, thirty-two 

 at 54°, &:c. Seth Green's rule is that at 50° they hatch in fifty days, 

 every degree warmer or colder making a diflerence of five days. After 

 the eggs are hatched the yolk sac is absorbed in from thirty to eighty 



