Under-ice diel vertical migrations of Oncorhynchus nerka and their zooplankton prey
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Date
1999
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Abstract
We used stationary hydroacoustics and measures of environmental conditions (water temperature, dissolved oxygen, light levels, and zooplankton) to determine what factors, foraging or predation risk, influenced die! vertical migrations of Oncorhynchus nerka during winter in three high-mountain lakes. The Sawtooth Valley lakes are deep,
oligotrophic, glacial lakes located in central Idaho, U.S.A., and historically contained populations of anadromous
O. nerka. In general, low light intensities limited foraging opportunities of O. nerka under ice, especially at night. In
Stanley Lake, O. nerka underwent diel vertical migrations to exploit available light to feed. Oncorhynchus nerka
occupied shallow water at night, where there was still sufficient light to feed, but were found in deep water during the
day. It is unknown whether O. nerka occupied deep depths during the day to feed on high densities of zooplankton or
to avoid predators. In Alturas Lake, O. nerka remained in the top 25 m both day and night to feed high densities of
zooplankton found near the surface. In Redfish Lake, O. nerka also showed little migration: O. nerka stayed in shallow
water both day and night and occupied the same depths with the highest zooplankton densities. The vertical
distribution of O. nerka during the winter appears to be determined by available food and light, but the deep daytime
distribution found in Stanley Lake is still unexplained.
Description
Abstract in English and French.
Keywords
Oncorhynchus nerka, Stanley Lake, diel vertical migrations
Citation
Steinhart, Geoffrey B.; Wurtsbaugh, Wayne A. "Under-ice diel vertical migrations of Oncorhynchus nerka and their zooplankton prey," Canadian Journal of Fisheries and Aquatic Sciences, v. 56, no. S1, 1999, pp. 152-161.