Trends in Run Size and Carrying Capacity of Pacific Salmon in the North Pacific Ocean

• Main Authors: Masahide Kaeriyama, Hyunju Seo, Hideaki Kudo
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: carrying capacity; long-term climate change; Pacific salmon; run size; Keta; Pacific; Sockeye; aleutian low; Pink salmon
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.183.23; http://www.npafc.org/new/publications/Bulletin/Bulletin%20No.%205/NPAFC_Bull_5_293-302%28Kaeriyama%29.pdf

Abstract: Pacific salmon (Oncorhynchus spp.) play an important role as keystone species and as ecosystem services in the North Pacific ecosystem. Our objective is to evaluate the trends in and causes of variation in run size and carrying capacity of Pacific salmon, and to predict their future production dynamics. Salmon catch data indicate that the abundance of Pacific salmon has declined since the end of the twentieth century, despite the healthy condition of stocks. At the beginning of the 21st century, chum (O. keta) and pink salmon (O. gorbuscha) maintained high abundance commensurate with a sharp increase in hatchery-released populations. However, sockeye salmon (O. nerka) have shown a reduction trend since the late 1990s. The abundance of coho (O. kisutch), Chinook (O. tshawytscha), and masu (O. masou) salmon, which spend more than one year in fresh water, has declined sharply since the 1980s due to degraded environmental conditions in freshwater habitats (e.g., habitat loss, urbanization, and river channelization). The significant positive correlation between the carrying capacity (K) of three species (sockeye, chum, and pink salmon), defined as the replacement level of Ricker’s recruitment curve, and the Aleutian Low Pressure Index (ALPI) indicate that their carrying capacity is synchronous with long-term trends in climate change. The carrying capacity of the three species is expected to continue the downward trend seen since the 1998/99 regime shift.