Evidence of growth-selective mortality of European anchovy larvae in the Bay of Biscay based on otolith microstructure analysis

Abstract

We tested the hypothesis that anchovy juveniles that survived until autumn in the Bay of Biscay were the larger and faster-growing members of their cohorts. Anchovy larvae and post-larvae were collected in August 2005 and juveniles in September-October 2005 in the south-eastern part of the Bay of Biscay. Their otoliths were analysed, and larval, post-larval, and juvenile hatch date distributions, as well as daily growth patterns, were estimated. Subsequently, larval growth trajectories of juveniles were compared with those of larvae and post-larvae from the same cohort. Additionally, a generalised additive mixed model was applied to characterize otolith growth trajectory. Juveniles exhibited higher growth rates than larvae and post-larvae, providing evidence of growth- selective mortality. These differences were observed from 16 to 20 days onwards and could be related to the onset of diel vertical migration and/or larval aggregation. Our results support the hypothesis that fast growth increases the survivorship of anchovy during the larval stage. These findings contribute to a better understanding of the role of predation pressure on anchovy survival in the Bay of Biscay.