Fishery bulletin of the Fish and Wildlife Service - NOAA

254 SALMON OF THE KARLUK RIVER, ALASKA
spawning grounds during the last of June and the peak of the spawning occurs during
the third week of July. These fish populate all the spawning streams entering the
lake and, to a slight extent, certain parts of the lake shores where seepage through the
gravel promotes conditions suitable for spawning. By the end of July or the first week
of August the fish have completed spawning, and there is a definite scarcity of live
fish on the spawning grounds. During late August, fish again appear in numbers on
10
17 24 3l 7 14 2l 28 б 12 19 26 Z 9 16 23 30 6 13 2O JL7 Л II
MAY JUNE JULY AUG. SEPT. OCT.
FiauBE 2.—Percentage of total run appearing each week during season.
the spawning grounds. An appreciable percentage of the fall run spawns along the
beaches, and some of the fish spawn in the Karluk River for a distance of a mile or two
below the lake, an area never populated by fish of the spring run. The majority of the
fish in the fall run do spawn, however, in the tributary streams of the lake.
Although the two runs of fish spawn, to a great extent, on the same spawning
grounds, the time interval precludes a thorough interbreeding of the two populations.
The only interbreeding possible is between the late spawners of the spring run and
the early spawners of the fall run. 'Whether'or not the separation between the two
groups has been sufficient to produce any anatomical differences that might be detected
biometrically has not been determined conclusively. Even though the differences
could not be detected biometrically, such an absence of differences would not repudiate
the theory of two populations of red salmon inhabiting one watershed and spawning
in the same gravel. Environmental conditions undoubtedly do account, in a large