| Summary: | [Missing any annual plankton and CTD data sets from this study] Prince William Sound (PWS) is one of the largest areas of protected waters bordering the Gulf of Alaska (GOA). It, and the nearby open waters of the Gulf, provide foraging areas for populations of apex predators including piscivorous seabirds and marine mammals. These surface- dependent predators were adversely impacted by the EXXON VALDEZ oil spill (EVOS); and many experienced declines from which they have not recovered. Piscivorous seabirds and marine mammals in PWS are near the apex of food webs based on pelagic production of small fishes, including Pacific herring (Clupea pallasi), Pacific sand lance (Ammodytes hexapterus), walleye pollock (Theragra chalcogramma), capelin (Mallotus villosus) and eulachon (Thaleichthys pacificus); and macroinvertebrates, especially euphausiids, commonly called krill. The lack of recovery by some seabirds may be due to long-term changes in forage species abundance. In this report we describe abundance and distribution patterns of small pelagic fishes in Prince William Sound, based on acoustic surveys. The research described in thls report was part of a program (APEX) designed to determine if prey availability is limiting the recovery of seabird populations that were impacted by the EVOS. The main tool for measuring the distribution and abundance of forage fishes is hydroacoustics. Hydroacoustics can measure horizontal and vertical abundance and biomass at scales not possible by traditional net sampling techniques, and has been used to quantify fish (Thorne et al. 1977, Thorne et al. 1982, Mathisen et al. 1978) and the spatial patterns of a variety of aquatic populations (Gerlotto 1993; Baussant et al. 1993; Simard et al. 1993). Ln Alaskan waters, acoustics have been used to measure biomass relative to tidally-generated frontal features (Coyle and Cooney 1993) and the relationship between murre foraging, tidal currents and water masses in the southeast Bering Sea (Coyle et al. 1992). Acoustic sampling cannot positively identify the species of targets; consequently, net sampling must be conducted concurrently with acoustics to identify species and to provide size distribution data necessary for biomass estimations. Sources: Haldorson, L. Shirley, T. 1995. Biomass and distribution of forage species in prince william sound, Exxon Valdez Oil Spill Trustee Council Annual Report (Alaska Predator Ecosystem Experiment 95163-A), Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks. Haldorson, L. Shirley, T. Coyle, K. Thorne, R.1996. Forage species studies in prince william sound, Exxon Valdez Oil Spill Trustee Council Annual Report (Alaska Predator Ecosystem Experiment 96163-A), Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks. Haldorson, L. Shirley, T. Coyle, K. 1997. Forage species studies in prince william sound, Exxon Valdez Oil Spill Trustee Council Annual Report (Alaska Predator Ecosystem Experiment 97163-A), Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks. Haldorson, L. Shirley, T. Coyle, K. 1998. Forage species studies in prince william sound, Exxon Valdez Oil Spill Trustee Council Annual Report (Alaska Predator Ecosystem Experiment 98163-A), Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks.
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