Fishery bulletin of the Fish and Wildlife Service - NOAA

292 SALMON OF THE KAKLTJK KIVER, ALASKA
average number of eggs per female, as reported by Gilbert and Rich (1927), is approximately
3,700. If the spawning fish are 56 percent females (table 30), then there would
be an average of 2,072 eggs per fish in the escapement. With a ratio of return to
escapement of 2 to 1 the mortality between eggs and seaward migrants would be 99.55
percent, while with a ratio of return to escapement as high as 4 to 1 the mortality
between eggs and seaward migrants would still be over 99 percent. Thus the mortality
rate of these salmon, during the fresh-water stage of their life history, is extremely high.
There are a number of factors which contribute to this terrific loss in fresh water.
Many eggs are destroyed by the spawning fish which, during their spawning activities,
dig out eggs laid by earlier spawners. While the eggs are being deposited and during
the incubation period, there is a loss caused by predators such as trout and birds.
Meteorological conditions during the incubation period affect the success or failure of
a brood year. Floods, dry spells, or freezing weather may affect the eggs adversely.
After hatching, the fry work their way out of the gravels of the spawning beds and,
if hi the tributaries, migrate downstream to the lake. Until the young fish distribute
themselves along the lake shores and seek shelter among the rocks and boulders on
the bottom, they are preyed upon by trout. During the next 2 or 3 years they are
subject to diseases and parasites, and many are devoured by fish-eating birds such as
mergansers and terns. Thus, there is a constant decimation of the popxilation, until
less than 1 percent of the possible number of progeny have survived to migrate to the
ocean.
Of the fraction of 1 percent of possible progeny which have survived to the seaward
migrant stage, 79 percent perish while in the ocean due to disease and natural enemies,
leaving only 21 percent of the seaward migrants (between 0.1 and 0.2 percent of the
possible number of progeny) to return as mature fish.
SUMMARY AND CONCLUSIONS
1. There has been a marked reduction in the abundance of Karluk River red
salmon since the inception of intensive commercial fishing in 1888. The average yearly
catch for the period 1888 to 1894, inclusive, was more than 1,000,000 fish greater than
the average yearly total run (catch plus escapement) for the period 1921 to 1936.
2. Karluk red salmon migrate to the ocean in their first to fifth year counting
from the time the eggs are deposited in the gravel of the spawning beds, the majority
migrating in then- third or fourth year.
3. From a few months to 4 years are spent in the ocean, after which the fish
return as adults to spawn.
4. While the fish range from 3 to 8 years of age at maturity, the 5-year age group
is usually dominant, followed in importance by the 6-year age group.
5. The number of fish in the spawning escapements during the period 1921 to
1936 has ranged from 400,000 to 2,533,402 and averaged 1,113,594.
6. The runs of red salmon at Karluk are bimodal, and it is considered that there
are actually two distinct runs, spring and fall.
7. The fluctuations in the ratio of return to escapement have been considerable,
and no correlation has been found between escapement and return. This is due in
part to unfavorable environmental conditions on the spawning grounds in certain
years.