NATURAL HISTORY OF THE QUINNAT SALMON. 
135 
for the purpose of covering the eggs, nor to make a space for them to lie in, but by 
the violent exercise to loosen the eggs from the ovaries. If the purpose were to 
cover the eggs it would be repeated every time any were deposited. Gravel does 
not drift so far as the eggs, and if such were the purpose it would not be accom- 
plished. Besides, it is almost impossible to cover eggs with gravel; the eggs, being 
almost as light 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, prevent s many eggs from floating away and being devoured 
by other fishes, but such are liable to be covered too deeply 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 fishes. The “nest” can hardly be made as a place for the 
eggs to lie in, for the current 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 b}^ a sportsman 
in order to get front bait. Like observations have been reported by other persons. 
Percentage 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 con- 
ditions must necessarily be very low. In artificial fertilization the ova and milt ai’e 
mixed together in a vessel, insuring a coating of milt or spermatized water over each 
ovum. In natural spawning the ova are caught 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. The following experiments throw some light on the question: 
To determine the percentage of fertilization under as nearly natural conditions 
as possible a box was built 4 feet wide, 14 feet long, and 15 inches deep, and a strong 
current of water turned through it,. About 5 inches of gravel was put in the upper 
three-fifths. A pair of salmon were placed in the box October 28, 1897. A female 
not quite ripe was selected, in order to allow a few days to become accustomed to 
the place. Pickets nailed to the side prevented the fishes from jumping out. By 
November 2 they seemed to be at home in the box, and their actions indicated that 
they wei’e ready to spawn. A few eggs were deposited the next day. On the 4th 
the male died, having become almost entirely covered with fungus in the one week. 
Another was put in immediately, but the spawning was interrupted, as it required a 
day or two to get used to the place. The female died November 12, having deposited 
but few eggs. No cause of death could be ascertained. Of the 512 eggs deposited, 
343 were killed while being deposited. Of the remaining 169, 129 or 76 per cent were 
fertilized. In the second attempt 82 per cent were fertilized. 
In 1898 a pair of salmon were put in a ravine with simply a rack to prevent 
their going downstream. No eggs were deposited. 
So far as the number of eggs killed is concerned this experiment is not a fair 
test. The level floor of the box made few eddies, and the eggs were washed into the 
corners and killed The percentage of fertilization would certainly be no greater 
