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The linkage between growth rate and feeding success has been shown to strengthen the effects of early growth rate on later growth rate in the early life history of fish. However, the growth–feeding linkage largely remains to be tested at the individual level within the same populations/cohorts. We examined the growth–feeding linkage for multiple populations/cohorts in Japanese anchovy Engraulis japonicus larvae and Pacific round herring Etrumeus micropus larvae, through otolith microstructure analysis, based on samples collected from the commercial fishery for larval fish in the Kii Channel, Japan. The three growth–feeding mechanisms, which are based on the respective potential advantages of larger somatic size, higher growth rate, and earlier morphological development for achieving feeding success, were tested to understand how growth rate relates to feeding success. The "somatic size" mechanism was supported for all of six samples for anchovy larvae and three of four samples for round herring larvae. The "growth rate" mechanism was supported for two of six samples for anchovy larvae and three of four samples for round herring larvae. The "morphological development" mechanism was supported for three of four samples for anchovy larvae and all of three samples for round herring larvae. Overall, the present analysis supported the growth–feeding linkage but revealed the dynamics of the growth–feeding mechanisms. All the mechanisms were shown to operate at least for certain populations/cohorts, but none of them were universally effective over all populations/cohorts across the two species. Understanding the dynamics of the growth–feeding mechanisms would provide precious hints for considering strategies of predicting recruitment dynamics. [ABSTRACT FROM AUTHOR]

Johan Hjort's "critical period" hypothesis, which postulates that year‐class strength is determined in the short period following the onset of exogenous feeding, has rarely been supported by empirical data. Instead, the current understanding is that recruitment is determined by cumulative mortality throughout early life. Recent studies relied on the measure of growth autocorrelation derived from otolith daily increment widths to test the link between growth rate achieved during the post‐hatch period and during subsequent phases of the larval stage. Based on this approach, we revisit the role of larval growth in driving survival potential in three clupeoid species: Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, and Pacific round herring Etrumeus micropus throughout the larval stage, using a combination of published datasets of otolith increment widths. Strong growth autocorrelation was detected for all three species throughout the larval stage, suggesting that initial growth determines to some extent growth rates achieved later in life. The extent of autocorrelation was reduced in sardine relative to anchovy and round herring at older ages. This interspecific difference could be attributed to differences in sensitivity to variability of environmental factors such as water temperature and food availability. The present findings suggest that the effect of early growth rate persists into later life stages for driving survival potential, which could reconcile the classic concept of "critical period" and the current "growth–survival" paradigm. [ABSTRACT FROM AUTHOR]