MEPS 403:219-230 (2010)  -  DOI: https://doi.org/10.3354/meps08461

ABSTRACT: To provide a key piece of information for understanding the functioning of the Bering Sea pelagic ecosystem, we estimated the biomass of immature chum salmon in the Bering Sea basin in autumn using a return-at-age analysis incorporated with the results of genetic stock identification studies. The estimated biomass was 742000 t in 2002 and 617000 t in 2003, which is possibly an underestimate because of the uncertainty of trawl selectivity parameters used in the estimation. Although chum salmon has been the dominant nekton species in the pelagic ecosystem of the Bering Sea basin in recent years, biomass estimates for the species were smaller than one-tenth of the maximum biomass of walleye pollock in the 1980s. Previous studies have highlighted the importance of the huge biomass of mesopelagic planktivores, such as myctophid fishes and gonatid squid, to the ecosystem function of the pelagic Bering Sea. Planktivorous Pacific salmon including chum and pink salmon may also play a significant role as competitors and predators of small planktivores, thus affecting the dynamics of ecosystem function and nekton community structure in the pelagic Bering Sea.

KEY WORDS: Pelagic ecosystem · Planktivores · Biomass estimate · Salmon · Catch-at-age analysis · Genetic stock identification · Markov chain Monte Carlo