NATURAL HISTORY OF THE QUINNAT SALMON. 
125 
indicates an attempt to go downstream. They may frequently be seen coming 
downstream toward the rack, though I have never seen any try to get through it. 
When they get close enough to the rack to feel the force of the swift current, they 
always try to turn back. Eventually they become so weak that they are unable to 
keep from being carried onto the rack, where many of them perish. 
There are also a few fishes that drop downstream as they become exhausted 
from long residence in fresh water; rarely from spawning. Such were found almost 
daily on the upper rack at Battle Creek fishery in 1900. Very few of them had 
spawned, though they were almost completely exhausted and hardly ever lived over 
a day after coming near the rack. Such specimens usually lie in the less swift 
water some 10 or 15 yards above the rack, where little effort is required to maintain 
a position. As they become weaker and the current carries them back toward the 
rack, they swim back and forth across the creek, their bodies set obliquely to the 
current, and their tails frequently almost touch the rack. A very little of such 
exertion soon exhausts them, and frequently they go but a few feet before being 
carried against the rack, where they die in a few minutes. 
Relation between weather and migration . — It is popularly supposed that the 
movement of salmon in the rivers is largely determined by weather conditions. 
Almost any fisherman can tell of a notable run of salmon that accompanied or fol- 
lowed a south wind. Observations made during two years at Battle Creek fishery 
show that there is no relation whatever between the direction of the wind and the 
movements of salmon. A strong wind of any direction, however, does apparently 
cause them to move upstream when they have been lying in a pool for some time. 
The most notable movement at Battle Creek fishery in 1898 was coincident with a 
strong north wind. A rain or a slight rise in the water usually causes them to run 
upstream, but not always. There is apparently no relation whatever between 
weather conditions and ripening of fish. 
CHANGES IN SALMON AFTER ENTERING FRESH WATER. 
The alimentary canal . — It is not uncommon for fishes of the salmon family to 
fast during the breeding season. Such is the case with the Atlantic salmon, the 
various white-fishes of the Great Lakes, and probably with other species, and it is 
well known that adult Pacific salmons do not eat while in fresh water. The Sacra- 
mento salmon will often snap at bright floating objects and can frequently be taken 
with the spoon while on their spawning-grounds or while passing up the river. 
Seventy-five specimens were taken in this way at Jelly Ferry during October and 
November, 1900. They have never been known to take food, though indigestible 
material, such as leaves, is sometimes found in the stomach, A 13-inch, mature, 
sea-run male salmon was taken at Battle Creek fishery in October, 1898. The 
stomach was contracted the same as in the ordinary adults, but contained two small 
bits of ehitinous substance looking somewhat like portions of the thorax of a grass- 
hopper, but may have been portions of a crustacean. 
As they do not eat after leaving salt water, the digestive organs immediately 
begin to shrivel up. In most of the specimens of the fall run that reach the head 
of Suisun Bay the stomach and cieca have already contracted and their walls have 
become firm. Only rarely are they thin and flaccid, as if food had recently been 
