Growth and maturation of Korean chum salmon under changing environmental conditions

Abstract

Salmon populations in the North Pacific have been subject to major changes in environmental and fishing pressure since the early 1980s, including a climate regime shift in 1988–1989, the closure of the high-seas fisheries in 1993, and a subsequent climatic event in 1998. In the present work, we evaluate whether any of these three events has triggered changes in the life-history traits of chum salmon (Oncorhynchus keta) from the Namdae River, on the eastern coast of South Korea, using data collected on females and males from 1984 to 2008. We find that the 1988–1989 regime shift had the most pervasive effects on female and male maturation schedules and growth. We also demonstrate sex-specific responses: whereas growth showed similar patterns of variation in both sexes, age and length at maturation behaved differently in males and females. Our findings contribute to growing evidence that abrupt transitions in climatic conditions can trigger detectable changes in life-history traits. They also strengthen the observation that biological records of salmon populations of the North Pacific carry a stronger signal for the effects of the 1988–1989 regime shift than for the effects of the subsequent environmental changes.