| Summary: | Study History: This investigation was initiated with a detailed study plan that subsequently became Fish/Shellfish Study Number 27. The initial research plan coupled parallel investigations on Kenai/Skilak Lakes in Cook Inlet with Red and Akalura lakes on Kodiak Island. A final report on F/S No. 27 was published by D.C. Schmidt and K.E. Tarbox within the Fisheries Rehabilitation, Enhancement and Development Report series (No. 136) titled Sockeye Salmon Overescapement. Subsequent studies (93002, 94258, 95258, 96258 and 97251) focused on restoration efforts which consisted of continued monitoring of the affected populations with an interim ADF&G Regional Information Report (No. 5J95-15) published by Schmidt et al. (1995). The data collected from Kodiak Archipelago sockeye populations were included in these reports while publications focused solely upon Kodiak Island sockeye data with limited analyses have also been generated: Barrett et al. (1993a, 1993b); Swanton and Nelson (1995); Swanton et al. (1996). Abstract: The impacts of large escapements on sockeye salmon (Oncorhynchus nerka) systems with freshwater production constrained by limitations on lake rearing capacity were substantiated with empirical data for several Alaskan stocks. As a result of the Exxon Valdez oil spill, Red and Akalura lakes on Kodiak Island received escapements that were 2X the upper end of the escapement goals. Data collected were macrozooplankton biomass, species composition and size structure along with abundance and size of rearing fry and smolt. Two sockeye salmon systems, Upper Station and Frazer lakes, were used as controls. Zooplankton density and biomass decreased at both Red and Akalura lakes when fry from the 1989 brood year were present, however only the decrease for Akalura Lake sockeye was statistically significant. Rearing fry population estimates for both study lakes were deemed of low utility owing to numerous instances where they were less then subsequent smolt population estimates. Sockeye smolts from the 1989-1991 brood years exhibited increased percentages of age-2 fish alluding to the rearing environment having been impacted by heightened foraging of rearing fry. These results although not definitive, suggest that a depression in the rearing environment was caused by the 1989 escapement event and persisted through 1992.
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