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White seabass, Atractoscion nobilis , is an important coastal resource throughout both California and Baja California, but whether this species comprises a single or multiple subpopulations in the northeastern Pacific is not known. The aim of this study was to infer larval rearing habitats and population structure of white seabass by sampling adults from three regions spanning a latitudinal temperature gradient and a distance of over 1000 km, and analyzing the isotopic composition (δ 18 O and δ 13 C) of otolith aragonite corresponding to the larval, juvenile and adult stages. Otolith cores revealed high isotopic variability and no significant differences among regions, suggesting overlapping rearing conditions during the larval stage, the potential for long distance dispersal or migration or selective mortality of larvae at higher temperatures. Back-calculated temperatures of aragonite precipitation derived using regional salinity-δ w relationships and local salinity estimates also did not differ significantly. However, there were significant differences between the δ 18 O values of the first seasonal growth ring of age 0 fish as well as back-calculated aragonite precipitation temperatures, suggesting the presence of two potentially discrete subpopulations divided by Punta Eugenia (27°N) along the central Baja California peninsula. These findings are consistent with regional oceanographic patterns and are critical for understanding white seabass population structure, and provide information needed for the implementation of appropriate management strategies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]