REPORT OF STATE BOARD OF FISH COMMISSIONERS 97 



On account of the difficulty in seeing eggs under water, it has been 

 impossible to determine the rate at which ova are deposited. The 

 motions of the fish show just when ova are being extruded, but observa- 

 tion a1 a distance of 5 feet, with the aid of a field glass, lias failed to 



disclose the ee-'j'S. 



Tbe female a1 irregular intervals turns over on her side and digs her 

 tail into the gravel. If the gravel is fine there is often a considerable 

 hillock thrown up, leaving a hole 6 or 8 inches deep and 2 feel across. 

 This digging is probably not for the purpose of covering the eggs, nor 

 to mfikc a space for them to lie in. but by the violent exercise to loos 

 the eggs from the ovaries. If the purpose were to cover the eggs it 

 would be repeated every time any were deposited. Gravel does no1 

 drift as far as the eggs, and if such were the purpose it would not be 

 accomplished. Besides, it is almosl impossible to cover eggs with gravel; 

 the eggs, being almost as lighl as the water, slide away from the gravel. 

 .More than that, a covering of over an inch of even fine gravel kills 

 them. The hillock, by forming an eddy at the bottom of the stream, 

 prevents many eggs from floating away and being devoured by other 



fishes, but such are liable to be covered t leeply and killed in that 



way. Some of the fine sediment, however, may settle on the eggs and 

 tend to make them invisible to egg-eating Ashes. The "nest" can hardly 

 be made as a place for the eggs to lie in, for the cm-rent always carries 



them below it. 



The presence of the other sex is not necessary to excite either to 

 spawning efforts. I have seen the female spawning alone at Battle 

 Creek fishery, and other persons have reported similar observations 

 from other places. In September, 1900, I saw a male spawning alone 

 near Sims, the female having been killed by a sportsman in order to get 

 trout bait. Like observations have been reported by other persons. 



Percentagt of Fertilization. — As one pair of salmon deposits an 

 average of 6,000 eggs the increase would be enormous unless there was 

 great loss at some period. It is usually supposed that the greater part 



of this loss is due to a lack of fertilization of the ova. The great care 

 necessary to secure perfect fertilization artificially has led fish-culturists 

 to suppose that the percentage of fertilization under natural conditions 

 must necessarily be very low. In artificial fertilization the ova and 

 milt are mixed together in a vessel, insuring a coating of milt or sperma- 

 tized water over each ovum. In natural spawning the ova are cauJu 

 in the eddies among the rocks, either near the nest or within a few yards 

 below it. A few seconds after the ova are spawned a small quantity of 

 milt is disseminated in the current to be carried against them. It seems 

 very unlikely that a large percentage could be fertilized under such 

 conditions. 

 7— fc 



