Cyclic Fluctuations in Chum Salmon Abundance along the Pacific Coast of Hokkaido, Japan

• Main Authors: Toshihiko Saito, Kyuji Watanabe, Kei Sasaki, Shigeto Kogarumai, Shoko H. Morita
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: chum salmon; pink salmon; coastal sea surface temperature; scale pattern analysis; odd- and even-year fluctuation; Okhotsk; Pacific; Salo; Pink salmon
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.434.7158; http://www.npafc.org/new/publications/Technical Report/TR8/Saito et al.pdf

Some chum salmon stocks are known to exhibit a two-year cyclic variation in their biological parameters, such as age at maturity, size, marine survival, and abundance (Salo 1991). Previous studies suggest that this variation appears to be associated with pink salmon, which have a prominent two-year cyclic pattern of abundance (Salo 1991; Ruggerone and Nielsen 2004). On the Pacific coasts of Hokkaido (East Pacific, EP; West Pacific, WP) abundance of adult chum salmon, calculated on the basis of coastal and river catches, shows odd- and even-year fluctuations after the 1998 brood year. A similar fluctuation is also observed in chum salmon caught in the southern region of the Sea of Okhotsk, adjacent to the Nemuro Strait (Nemuro, NE). The objective of this study was to explain a possible mechanism causing the cyclic pattern of returning adult chum salmon. Of 48 chum salmon river-stocks along the Sea of Okhotsk and Pacific coasts of Hokkaido, 11 stocks from the Pacific coast illustrate cyclic fluctuations in abundance for brood-years 1998-2004. Only one stock from the Sea of Okhotsk exhibit these cyclic fluctuations. Findings demonstrated that a few stocks from rivers on the Pacific coast cause the cyclic patterns in brood-year abundance in the NE, EP, and WP regions. In general, mass mortality of chum salmon occurs during early marine residence and frequently affects the brood-year abundance of returning adult salmon (Saito and Nagasawa 2009; Saito et al. 2011). The mass mortality is believed to be associated with biological interactions, like predation (Duffy and Beauchamp 2008), and oceanic conditions (Saito et al. 2011). In this study, effects of Asian pink salmon and sea surface temperature