John Wiley & Sons, Ltd.

Comparative organochlorine accumulation in two ecologically similar shark species (Carcharodon carcharias and Carcharhinus obscurus) with divergent uptake based on different life history

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Trophic position (TP) and body mass are traits commonly used to predict organochlorine (OC) burdens. Sharks, however, have a variety of feeding and life‐history strategies, and metabolize lipid uniquely. Because of this diversity, and the lipid‐association of OCs, the dynamics of OC accumulation in sharks may be ineffectively predicted by stable isotope‐derived TP and body mass as is typical for other taxa. This study compared ontogenetic OC profiles in the dusky (Carcharhinus obscurus) and white shark (Carcharodon carcharias), which differ in metabolic thermoregulation and TP throughout their ontogeny. While greater OC concentrations were observed in the larger bodied and higher TP white shark (e.g., p,p'‐DDE: 20.2 ± 2.7 ng/g, vs. 9.3 ± 2.2 ng/g in the dusky shark), slopes of growth‐dilution corrected concentrations with age were equal to those of the dusky shark. Similar ontogenetic TP increases in both species, less frequent white shark seal predation than previously assumed, or inaccurate species‐specific growth parameters are possible explanations. Inshore habitat use (indicated by δ13C values) and mass were important predictors, in white and dusky sharks respectively, both of overall compound profiles and select OC concentrations. This study clarified our understanding of TP and body mass as reliable predictors of interspecific OC accumulation in sharks, whereas regional endothermy and diet shifting were shown to have less impact on overall rates of accumulation. This article is protected by copyright. All rights reserved

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