Growth of Atlantic Bluefin Tuna: Direct Age Estimates

New models were fit for recent samples of Atlantic bluefin tuna on the basis of annulus interpretations in otoliths. Samples were specified further based upon whether individuals originated in western or eastern nursery systems using otolith stable isotope analysis. A model fit to recent year-classes (after 1970) for western captured, western-origin Atlantic bluefin tuna yielded von Bertalanffy coefficients of K=0.20; L∞=257; and t0=0.83. These coefficients are substantially different than those from the Turner and Restrepo model (K=0.08; L∞=382; t0= -0.71), and predicts lengths at age which are similar to about age 12, but increasingly divergent at greater ages. Growth models were also fit for the eastern population, but coefficients were probably biased due to the small sample size. Given the established accuracy of direct age estimates from otoliths and the feasibility of complementary age and natal assignment determinations using the same prepared otoliths, we recommend future assessments be based upon direct ageing of otoliths over other approaches.