SALMON AND TROUT— SCHULTZ 375 



Usually the eggs are well covered within an hour or two to a depth of 

 2 inches or more. This post-spawning behavior offers distinct advan- 

 tages for the protection of the eggs and recently hatched fry, as 

 pointed out by Needham (1934, p. 336) who says: "Eggs laid in the 

 first portions of the nest are gradually buried deeper and deeper by 

 materials being washed downstream from pits dug above as she works 

 upstream." The eggs remain in the nests covered with gravel until 

 hatched. The oxygen supply needed by the eggs and young trout 

 dm-ing their development in the gravel is supplied by the seepage of 

 water through the loose material of the stream bottom. The time 

 required for the eggs to hatch depends on the species as well as on the 

 water temperature. Eggs laid in cold water take longer to hatch than 

 those laid in warmer water, the time varying from 2 or 3 weeks to 6 or 

 8 months. The baby salmon or trout after hatching remain in the 

 gravel until their yolk sack has been absorbed, then they gradually 

 make their way through the gravel into the water of the stream. 



DESTRUCTION OF EGGS 



The eggs, after being covered by the female, are relatively safe from 

 predatory animals. However, when first laid, some may be swept 

 from the nest pit by the current. Should any of these escape the 

 mouths of fish lurldng in the vicinity ready to eat them, they would 

 never develop for they would be carried to the pools below, where the 

 eggs would settle to the bottom, gradually becoming covered with 

 sediment that would cause them to be suffocated. Other hazards 

 await the eggs. Fungus often attacks them and may spread through 

 the nest when the eggs are too crowded, but it can make little headway 

 when they are well separated. Freshets often wash out the eggs of the 

 salmon and trout, and once they are removed from the nest they have 

 little or no chance of survival. In certain areas the streams recede 

 after the trout have spawned, leaving the nests high and dry, which 

 soon kills the eggs. These, among other dangers, take their toll of 

 the new crop of eggs and young fish planted so carefully by the 

 mother. 



LITERATURE CITED 



Davidson, Frederick A. 



1937. 'S Migration" and "homing" of Pacific salmon. Science, vol 86, 

 pp. 55-56. 

 Gilbert, Charles Henry. 



1923. The salmon of the Yukon River. Bull. U. S. Bur. Fish. 1921-1922, 

 vol. 38, pp. 317-332, figs. 274-300. 

 Greeley, John R. 



1932. The spawning habits of brook, brown, and rainbow trout, and the 

 problem of egg predators. Trans. Amer. Fish. Soc, vol. 62. pp. 

 239-248. 



