Graduate Thesis Or Dissertation
 

Biology of juvenile sockeye salmon resident in Chignik River, Alaska

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8049g7411

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  • The life history of juvenile sockeye salmon (Oncorhynchus nerka) resident in Chignik River, Alaska, represents a departure from the lacustrine, pelagic existence typical of juveniles of this species. For this reason, the distribution, relative abundance in different parts of the river, growth, and upstream and downstream movements of juvenile sockeye in the river were studied during the summers of 1963 and 1964. The objectives of the study were to gain information on the possible origins of juvenile sockeye resident in Chignik River, and on the role of Chignik River in production of sockeye salmon. Distribution and abundance were estimated by seining and underwater observation. Juvenile sockeye appeared to be restricted to quiet waters along the shore. Catches of sockeye fry tended to increase through the summer, whereas catches of yearlings decreased. Smolts were taken in significant numbers only in June and July. early summer, large numbers of yearling sockeye were concentrated in Chignik River just below the outlet of Chignik Lake. In Sockeye fry and yearlings captured in the lower river were generally larger than those captured in the upper river. Juvenile sockeye in the upper river grew slower than those in most other parts of the watershed. Scale analysis of sockeye salmon spawning in Chignik River showed that these fish entered the ocean at a larger size than did fish reared in Chignik Lake or Chignik River. This suggests that at least part of the progeny of river spawners do not remain in the river, but descend as fry to the brackish estuary, where growth conditions are superior. Upstream movement of schools of yearling sockeye was observed in the upper portions of the river. Such a movement has been observed many times in Chignik River in past years and has at times involved large numbers of fish. Schools of yearling sockeye have been observed to enter Chignik Lake. Fish of the same size group were captured while moving downstream at the lake outlet at night, suggesting a circular movement involving displacement of fish into the river at night and a positive rheotactic response causing them to re-enter the lake during the day. Juvenile sockeye salmon resident in Chignik River may include both progeny of river spawners, and fish which have moved down from Chignik Lake; Chignik Lake is probably the more important source. Chignik River is judged to have a minor role in the production of sockeye salmon, relative to the other rearing areas in the watershed.
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