Linking Early Growth Rate and Recruitment Variability of Japanese Anchovy ( Engraulis japonicus ) in the Central Seto Inland Sea, Japan

Early growth rate in small pelagic fish is influenced by both exogenous and endogenous factors, and faster growth within a cohort is generally associated with higher survival and successful recruitment. In the central Seto Inland Sea, Hiuchi‐Nada, western Japan, recruitment of Japanese anchovy ( Engraulis japonicus ) has markedly decreased over the past decade due to reduced early‐life survival. This study assessed the link between early growth rate and recruitment indices by comparing growth rates of recruits between periods of high (2002–2006) and low (2013 and 2015–2019) recruitment. Growth rates were significantly lower during the low recruitment period, with fish exhibiting only about 80% of the growth rate observed during the high recruitment period at a given temperature. A time‐series analysis revealed that prey biomass per spawning female, maternal condition factor, and nauplius density per larval density declined over the study period, while temperature increased. During the low recruitment period, recruits generally exhibited higher early growth rates than larvae (original population) of the same age, suggesting that faster growing individuals were more likely to survive. However, in 2017, the highest growth rate among recruits coincided with the lowest recruitment and survival indices, implying that the elevated growth may have resulted from growth‐selective mortality favoring a small subset of rapid‐growing individuals under intense top‐down pressures. These findings suggest that the recent decline in early growth rates may be attributable to deteriorating maternal conditions and increased intracohort competition for prey under warming conditions, while year‐specific growth‐selective mortality may further shape recruitment outcomes.