Growth of chum salmon (Oncorhynchus keta) correlated with sea-surface salinity in the North Pacific

Abstract

The average adult size-at-return of North Pacific salmon (Oncorhynchus spp.) has decreased since the 1970s and several hypotheses regarding the cause of this decrease have been proposed. These have included fishing pressure, change of sea-surface temperature (SST) and density-dependence. This paper re-examines recent trends in the catch per unit effort (cpue) of chum salmon (Oncorhynchus keta), SST, sea surface salinity (SSS) and the Aleutian Low Pressure Index (ALPI), and compares them with trends in growth to determine if any of these factors related to the growth of chum salmon in the Sub-Arctic Domain of the Western North Pacific. From 1979 to 1998 chum salmon cpue increased, but fork length and back-calculated year-specific growth-increment size decreased significantly. SST showed no consistent pattern but SSS decreased significantly over time. Of total salmon cpue, chum salmon cpue, SST and SSS, only SSS was significantly correlated with growth-increment size; this relationship was positive. Residuals of the year-SSS relationship were also correlated with residuals of the year-growth increment-size relationship, indicating that SSS was consistently linked to growth-increment size. 2001 International Council for the Exploration of the Sea