38 
FISHERIES OF ALASKA IK 1909. 
may be taken by the industry without reducing the productivity. It 
is to be remembered that these figures represent highly probable ex- 
tremes and that the present actual rate of increase is somewhere 
intermediate. 
It would be necessary only to count the escape in both Nushagak 
and Wood rivers for seA 7 eral years to arrive at practically accurate 
knowledge of the rate of increase for the Nushagak region. The 
two minor rivers carry so small a part of the total that estimates 
made from a knowledge of fishing experience in them are entirely 
sufficient to prevent important error. This rate of increase may, then, 
be expected to apply without great modification to other red salmon 
fisheries. 
These calculations assume in theory that all the progeny of the 
spawning grounds of the Nushagak basin, and no others, return as 
adults to Nushagak Bay. This is not entirely true, for chance and 
physical conditions probably determine to some extent which indi- 
viduals and how many shall diverge from their course up Bristol 
Bay and enter Nushagak Bay instead of continuing to the fisheries 
at the head of Bristol Bay. There must be some interchange between 
the several regions of Bristol Bay fisheries. As affecting the determi- 
nation of the rate of increase this is a difficulty which at present can 
not be met. It need occasion no anxiety, for it is almost obvious 
that in the long run regions such as the Nushagak depend on their 
ow T n spawning grounds for maintenance. The exchange between the 
fisheries is reciprocal. 
Miscellaneous observations . — As in 1908, all species of Pacific 
salmon were seen at the lake, also several other species of fishes. 
Salmon other than red salmon were many fewer than during the 
preceding year and were unimportant in either season. The Dolly 
Varden trout was also less numerous. 
A tally of the salmon showing the twine marks of the gill nets 
was made on several different days at times of both light and heavy 
runs. The percentage of twine-marked fish ranged from 2 per cent 
at the height of the run up to 15.6 per cent on July 19, the last day 
on which such a count was made. These percentages were somewhat 
higher in 1908,' though the proportion of the run taken was smaller. 
One of the most important and impressive differences between the 
two seasons, observed during the examination of the lake and its 
creeks and of Wood River, was in the abundance of salmon fry. No 
one familiar with the waters in both seasons could fail to be im- 
pressed by the great increase in the number of small redfish fry — 
young of that season — during the 1909 summer as compared with the 
previous one. They were caught in the muddy waters of the upper 
