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Evaluation of growth-dependent survival during early stages of Pacific bluefin tuna using otolith microstructure analysis
This study employed otolith analysis-based body size back-calculation to evaluate the hypothesis of growth-dependent survival in young Pacific bluefin tuna (PBF; Thunnus orientalis) from the northwestern Pacific Ocean, to identify critical developmental stages for survival, and to compare interannual differences in early growth. For these purposes, we compared the daily growth trajectories of a large number of larvae (standard length, SL<15 mm), juveniles (15≤SL≤150 mm), and young-of-the-year (YOY; SL>150 mm) collected between 2011 and 2015. Otolith radius and SL were highly correlated and yielded a single relationship applicable for the five yearclasses. Body size back-calculation showed that only larvae with fast, steady growth successfully transitioned to the juvenile stage. Otolith increment analysis, used as a proxy for daily growth rates, revealed interannual differences only in larvae but not in the larval stage of juveniles and YOY. Neither sudden decreases nor increases in otolith increment were observed during the larval stage of any of the stages, suggesting that the observed variability in larval body size may be the result of individual differences in growth rates rather than of drastic, one-time events. Overall, the results of this study indicate that growth-dependent survival of larvae may be the most critical for PBF recruitment.
MF16337 Accepted 04 February 2017
© CSIRO 2017