Incorporating thermal niche to benefit understanding climate‐induced biological variability in small pelagic fishes in the Kuroshio ecosystem

Abstract

AbstractClimate‐induced fluctuations in marine fish populations have been raising great scientific concerns. Previous studies generally dedicate to parameterization of climatic, environmental, and biological variability patterns with focuses on their empirical or incompletely mechanistic relationships. Little consideration on physiological characteristics of organisms prevents from exploring mechanisms behind the apparent relationships. Therefore, incorporating physiological information into investigation on climate–environment–biology relationships is essential to understand climate‐induced biological variability. Small pelagic fishes play unparalleled roles in the Kuroshio ecosystem and show dramatic fluctuations in response to environmental changes, serving as ideal research targets in studies on climate‐induced biological variability. This study focuses on Japanese sardine, chub mackerel, and Japanese anchovy, three key small pelagic fishes in the Kuroshio ecosystem with distinct physiological characteristics, with attempts to incorporate thermal niches into investigations on their responses to climate variability. The recruitment suitable index (RSI) is developed considering both sea surface temperature (SST) and species thermal niche. Results show that the RSI significantly increase explanations on variations in resource abundance indices of the three key small pelagic fishes. Responses of small pelagic fishes to climate variability show differences by species and stocks. In addition, variations in the Siberian High pressure system and Atlantic Multidecadal Oscillation contribute highly to variations in resource abundance indices through affecting the SST and further the RSI. This study demonstrates importance of physiological information for understanding climate‐induced biological variability and effectiveness of combining thermal niches with the investigation on mechanistic climate–environment–biology relationships, which should be extensively considered in the future studies.