116 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
This study shows that young salmon in fresh water feed exclusively on insects, 
and that immature aquatic insects form by far the larger portion of their food. The 
general summary of the table shows that approximately half of the food of the speci- 
mens studied consisted of pupae (or nymphs, which were not distinguished from 
pupae), one-third of larvm, and one-sixth of adult winged insects. 
There was an increase of flying insects in the food of specimens taken in Sulla- 
way Creek in August, and an increase in amount of food in specimens from Sims during 
July and August. It was during September, when apparently there was a scarcity 
of food, that the larger young salmon disappeared from Sims. There was an increase 
in flying insects in food of specimens from Hazel Creek in September; a scarcity of 
food and a noticeable lack of larvae in specimens from Battle Creek in October and 
November, and a smaller amount of food in specimens from the lower stations. (See 
summary for May, page 117.) 
Two specimens from above Bear Valley Dam, near Olema, taken January 18, 
1898, had stomachs gorged with larvae and pupae, one having about 50 of the former 
and 25 of the latter, but no indications of adult insects. 
Three specimens, Nos. 117, 118, and 137, of food table, were taken in October and 
November before the yolk was yet absorbed. One had nothing in its stomach; 
another had some food, but it was unrecognizable; the third had eaten one larva and 
two adult insects, besides some other food that was unrecognizable. This indicates 
that they begin feeding even before the yolk is all absorbed. 
The food data, if arranged according to size of fish, would give the following- 
average amounts per fish. This table shows that pupae and nymphs are the favorite 
food for all sizes. Those from 1.4 to 2 inches in length feed very little upon adult 
insects; the largest size feed very little upon larvae. 
Size. 
N umbei’ 
examined. 
Average number in 
sti imach. 
Larvae. 
Pup*. 
Adult 
insects. 
1.4 to 2 inches 
59 
4 
3 
(“) 
3.1 3 inches 
53 
4 
ti 
3 
3.1 4 inches _ 
48 
r> 
8 
2 
4.1 5 inches 
32 
3 
4 
1 
5.1 ti.3 inches ....... 
8 
1 
14 
8 
<’ Indicates an average of less than one. 
The following table brings together a statement, of the average amount of food 
found in the stomachs of the young salmon from various stations for the month of 
May, the only month in which we secured young salmon from many of the lower 
stations. The table indicates that the important food of the young salmon through- 
out, the basin in May was larva; and pupa;, of which there was an average of 4.4 of the 
former and 6.5 ot the latter per fish. The fish examined averaged 2.5 inches. It 
also shows there was a slightly smaller amount of food in specimens from the lower 
portion of ihe river. They were not starving, however, and there is no evidence 
that the passage down the river is detrimental on account of the lack of food. 
a indicates an average of less than one. The numbers in the columns headed 
“No food'' and “ Paiasites’’ indicate the number of fishes examined that had 
empty stomachs or parasites, as the case may be. The totals are taken from the 
complete table ot food, but only for the month of May, and are not the sums of the 
averages given in this table 
