NATURAL HISTORY OF THE QUINNAT SALMON. 
85 
estimate of the average number of alevins that a trout will eat in a day, at which 
rate each trout would destroy about 150 before the absorption of the yolk-sac; and 
1,000 trout would destroy 150,000 alevins. The lesson is obvious. 
Just here it may be well to state that in 1897, although only 150,000 fry — not 
alevins — -were planted in Olema Creek, large numbers of them were yet to be found 
in June following, and quite a number in August. In 1898, 850,000 alevins were 
planted in Olema Creek, and in June following there was a smaller number left in 
the stream than was found in August the year before. There are two ways to 
account for this. One is that the alevins were washed out to sea before they began 
swimming; but it is more probable that they were eaten by trout and sculpins. 
In the spring of 1898, 7,000,000 salmon were planted at the hatchery on Battle 
Creek about two weeks before the yolk-sac was absorbed. Although trout are not 
numerous there, the stream swarms with sculpins ( Coitus gulosu-s), salmon fry 
remaining from the season before, Sacramento pike ( Ptyclioclieilus grandis), black 
pike ( Ortliodon microlepidotus ), hitch (. Lavinia exilicauda), split-tail ( Pogonichthys 
macrolepidotus), and suckers ( Catostomus occidentalis). All of these, though they 
do not feed exclusively on animal matter, take salmon eggs and alevins when they 
can get them. The Sacramento pike is very destructive to young fish. The split-tail 
is the most numerous species, and lives on salmon eggs during the spawning season. 
Each day while the hatchery was in operation the bad or addled eggs picked 
from the hatching baskets were thrown into the stream. Usually they were thrown 
into a small brook near its entrance to the creek. In a very short time after 
emptying a can of eggs the split-tails always began to appear, running in from the 
creek. In a few minutes the water would be alive with them, almost a solid mass 
tumbling one over the other, splashing the water and crowding each other in their 
frantic efforts to get the eggs, until some were forced into the mud at the edge, 
while others were lifted upward till their backs or bellies were out of water, or one 
might get into a vertical position with its head or tail out of water. Frequently 
one would gorge itself till throat and mouth were so full that the passage of the 
water over the gills was shut off and it suffocated. It usually required about 5 
minutes to consume 5 gallons of eggs. 
Alevins are almost as helpless as eggs and fully as palatable, and there can be 
little doubt of their fate when planted in such an environment. 
Results of observations. — The egg and alevin stages are the periods in the life 
of the salmon when the care of the fish-culturist is most needed. The art of taking 
and caring for the spawn has been so perfected that the loss in hatching need not 
be over 10 per cent, and is often less. The loss of alevins, if thej" are retained in 
the hatching- troughs or nursery ponds, need not be over 2 per cent. If the young- 
are planted during the alevin stage, the loss is very great. If large numbers of 
alevins are released in unsuitable places, where the bottom is comparatively free 
from stones, and where such predaceous fishes as the split-tail and trout abound, the 
loss may even be greater than if the parent salmon had been allowed to take their 
natural course in spawning. 
Young salmon should never be planted until the yolk-sac lias entirely disap- 
peared and their swimming power has fully developed, even though they have to be 
fed a few days. There is no advantage in holding them after this time. 
