88 
BULLETIN OF THE UNITED STATES FISH COMMISSION. ' 
it was found they had eaten only caddis larvae and periwinkles. On the Upper 
Sacramento River I have examined many trout taken while the stream was full of 
the small salmon fry, hut have never found that they had eaten young salmon. 
The same is the case with the sculpin, and these are the only fishes to be feared in 
the Upper Sacramento. Farther down stream many of the smaller Sacramento pike 
have been examined, but none of them were guilty of eating young salmon. 
In the spring of 1899, while observing the migration of the salmon fry on the 
lower Sacramento River by means of a fyke-net trap, we occasionally caught cat-fish 
along with the young salmon. In every case it was found that the cat-fish had 
eaten salmon fry. Their capacity for young salmon was greater even than that of 
the trout for alevins. Several cat-fish 9 inches in length were found with over 60 
salmon fry in their stomachs, and one of this same size had eaten 86 of the fry 
which averaged a little over TV inches long. To determine whether the cat-fish 
captured the fry only while in the bag of the net we caught nearly 50 with hook and 
line. The stomach of none of them contained a young salmon. Thus it is evident 
that the cat-fish likes salmon fry and would catch them regularly if it could. It is 
too sluggish a fish, however, to catch salmon fry under ordinary circumstances. 
The only other fish at all likely to prey upon the young salmon in fresh water 
is the striped bass ( Roccus lineatus), which is found in the lower river and in large 
numbers in the brackish water of Suisun Bay. It is also found in San Pablo and 
in San Francisco bays. I have no information on the subject, except that the 
striped bass preys to a large extent on the carp in the sloughs of the lower rivers 
and in the salt or brackish water feeds almost exclusively on small crabs. It is 
significant, however, that both striped bass and salmon are increasing in numbers 
in California waters, the former enormously, and it can not, therefore, be very 
detrimental to salmon. Young pike, suckers, and split-tails are abundant in the 
waters inhabited by the bass, and all are sluggish in comparison with the salmon. 
It would seem that young salmon would be the last fish upon which 1 hey would prey. 
A young salmon is very active and strong and much more shy than even a trout of 
same size; after it has begun to swim about and feed it is perfectly able to take care 
of itself, and the number killed by enemies in the Sacramento is very small. 
MIGRATION OF FRY. 
In 01 'em a Creelc . — The first year at Olema 150,000 fry, and the second year 
.850,000 alevins, were released in Olema Creek. The stream was seined about a 
month after the fry were planted in 1897, and in 1898 about a month after the time 
when the fry should have begun swimming. Very few young salmon were taken in 
either year, and the results show that over 95 per cent had left the stream within 
the month. 
Battle Creek station . — The observations in Battle Creek were made while we 
were engaged with the hatchery experiments during October and November, 1898. 
In obtaining data concerning the young salmon we used a 50-foot seine such as was 
employed in nearly all of the investigations; but the most important device for this 
work was a trap which caught the young salmon as they were going downstream. 
The trap was made by sewing a piece of fine-meshed webbing across the mouth of 
the bag of a 30-foot seine and fixing a funnel to extend back into the bag from the 
middle of the webbing. It was set in a strong current just below the upper rack at 
