Otolith-based growth estimates and insights into population structure of White Seabass, Atractoscion nobilis, off the Pacific coast of North America

Abstract

White Seabass (Atractoscion nobilis; Sciaenidae) comprise an important commercial resource in the USA and Mexico, but there are few growth rate estimates and its population structure remains uncertain. Growth rates were estimated based on otolith analysis of fish collected at three locations spanning 1000-km. Variations in growth rates were assessed at the population level and by reconstructing individual growth trajectories. Seabass were sampled from fisheries operating off southern California (SC) and the northern and southern (NBC and SBC) Baja California peninsula from 2009 to 2012 (n=415). Ages ranged from 0 to 28-years, but fish >21-years of age were sampled infrequently. Size-at-age was highly variable, particularly for fish <5-years. White Seabass grew quickly during the first 8-years of life after which growth rates decreased considerably. Fitting the size-at-age data with the von Bertalanffy growth function and applying the likelihood ratio test to parameter estimates indicated that SC, NBC and SBC did not differ significantly in growth rates (0.18–0.19-yr−1) or asymptotic length (141-cm total length). Individual otolith growth trajectories showed high variability within regions and there were only significant differences in the average width of the first annuli. However, residual analysis of the average annual radii suggests fish from SBC had a larger size-at-age. Those differences may be related to the higher coastal temperatures found in southern coastal waters. Although growth rates may differ during the first year of life, findings suggest growth to be similar across the study range.