Inter-annual variation in the relationship between early growth rate and potential survival of the western sand lance Ammodytes japonicus in the Seto Inland Sea in western Japan

Abstract

This study examined whether the potential early survival of sand lance in the Bisan Strait, central Seto Inland Sea, can be explained by variations in the growth rate and duration in the early life stages. Otolith microstructure analysis was conducted to examine the growth trajectories of specimens collected in six sampling years: 2011–2014, 2019, and 2020. There were significant differences in the growth rates of larvae and juveniles among sampling years, but such differences were likely attributable to variations in temperature in given seasons. Relative growth rates standardized by temperature were negatively correlated with the duration of the larval stage, suggesting that faster-growing individuals at given temperatures had a shorter larval stage. In each sampling year, there was a significant relationship between standardized hatch date and relative growth rate during the larval stage but not the juvenile stage. Within a given season, later-born larvae seemed to grow faster relative to the temperature experienced, and the higher percentages of the faster-growing larvae were likely associated with higher recruitment and recruitment per egg production. These findings suggest that the proportion of faster-growing sand lance larvae in a cohort at given temperatures explains the variation in potential early survival, but the higher temperatures in recent years may not necessarily contribute to improved early survival.