Numbers and Biomass of Natural‐ and Hatchery‐Origin Pink Salmon, Chum Salmon, and Sockeye Salmon in the North Pacific Ocean, 1925–2015

Abstract

AbstractNumerical abundance and biomass values presented here for Pink Salmon Oncorhynchus gorbuscha, Chum Salmon O. keta, and Sockeye Salmon O. nerka in the North Pacific Ocean span 90 years (1925–2015), representing the most comprehensive compilation of these data to date. In contrast to less populous species of salmon, these species are more abundant now than ever, averaging 665 × 106 adult salmon each year (1.32 × 106 metric tons) during 1990–2015. When immature salmon are included, recent biomass estimates approach 5 × 106 metric tons. Following an initial peak during 1934–1943, abundances were low until the 1977 regime shift benefited each species. During 1990–2015, Pink Salmon dominated adult abundance (67% of total) and biomass (48%), followed by Chum Salmon (20%, 35%) and Sockeye Salmon (13%, 17%). Alaska produced approximately 39% of all Pink Salmon, 22% of Chum Salmon, and 69% of Sockeye Salmon, while Japan and Russia produced most of the remainder. Although production of natural‐origin salmon is currently high due to generally favorable ocean conditions in northern regions, approximately 60% of Chum Salmon, 15% of Pink Salmon, and 4% of Sockeye Salmon during 1990–2015 were of hatchery origin. Alaska generated 68% and 95% of hatchery Pink Salmon and Sockeye Salmon, respectively, while Japan produced 75% of hatchery Chum Salmon. Salmon abundance in large areas of Alaska (Prince William Sound and Southeast Alaska), Russia (Sakhalin and Kuril islands), Japan, and South Korea are dominated by hatchery salmon. During 1990–2015, hatchery salmon represented approximately 40% of the total biomass of adult and immature salmon in the ocean. Density‐dependent effects are apparent, and carrying capacity may have been reached in recent decades, but interaction effects between hatchery‐ and natural‐origin salmon are difficult to quantify, in part because these fish are rarely separated in catch and escapement statistics. The following management changes are recommended: (1) mark or tag hatchery salmon so that they can be identified after release, (2) estimate hatchery‐ and natural‐origin salmon in catches and escapement, and (3) maintain these statistics in publicly accessible databases.