Quantitative estimation of the ecosystem services supporting the growth of Japanese chum salmon

Abstract

Chum salmon (Oncorhynchus keta) are distributed widely in the subarctic North Pacific. The Japanese stock is maintained by artificial release procedures. Chum salmon, including the Japanese stock, provide important ecosystem services for humans that are related to provisioning, culture and support. These ecosystem services are supported by the supply of prey and habitat that the fish use. We regard the supply of prey and habitat as supporting services for salmon. We developed a procedure to estimate supporting services quantitatively, based on the prey biomass consumed by individual salmon, by coupling a bioenergetics model and a lower trophic level ecosystem model. Using this procedure, we estimated the prey biomass consumed by a cohort of Japanese chum salmon released in a single year. The phytoplankton biomass indirectly consumed by a cohort was also estimated and considered to be the primary production supporting the fish. The Japanese chum salmon cohort was estimated to consume ca. 4.2–4.7 × 109 kg wet weight of zooplankton, of which more than half is eaten in the Bering Sea. The Japanese chum salmon cohort is supported by an estimated primary production of 2.0–2.2 × 109 kg C, which amounts to 0.17%–0.19% of primary production in the areas and periods through which the fish migrate. We also attempted to calculate the monetary value of supporting services for the growth of Japanese chum salmon.