Walleye pollock as predator and prey in the Prince William Sound ecosystem

Walleye pollock as predator and prey in the Prince William Sound ecosystem

R.E. Thorne

Walleye pollock as predator and prey in the Prince William Sound ecosystemThis is part of Resiliency of Gadid Stocks to Fishing and Climate Change
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Description

Research during the Sound Ecosystem Assessment (SEA) Program during the mid-1990s identified walleye pollock and Pacific herring as the two major pelagic fish biomasses in Prince William Sound. Pollock predation was also identified as a major source of mortality on juvenile pink salmon. Subsequent research at the Prince William Sound Science Center has focused on three aspects of the role of pollock in the Prince William Sound ecosystem: (1) winter-period population abundance, (2) pink salmon predator monitoring, and (3) marine mammal predation studies. Prince William Sound Science Center conducted winter-period surveys of adult pollock from 1995 to 2003. Pollock biomass in Prince William Sound ranged from 22,000 to 43,000 metric tons. The pink salmon predator monitoring studies assessed pelagic fish abundance and distribution synoptic with spring-period zooplankton surveys from 2000 to 2006. Both pollock and herring showed progressive migrations during the spring that were consistent with predation on inshore fishes
including pink salmon fry. Marine mammal assessment was added to the winter-period surveys beginning in 2000. Steller sea lion abundance and distribution were positively correlated with herring and negatively correlated with pollock. Walleye pollock and Pacific herring exhibit major differences in overwintering distributions that have substantial impacts on predator populations, especially marine mammals and seabirds. The difference in relative dominance between these two species
is likely a major factor in long-term ecosystem change.

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