Loggerhead marine turtle (Caretta caretta) ecological facts from a trophic relationship model in a hot spot fishery area: Gulf of Ulloa, Mexico

Abstract

The oceanographic conditions in the Gulf of Ulloa (GU) region make a distinctive faunal assemblage, allowing the presence of species both ecologically and economically important. Constant interaction of emblematic species with the fishing activity has brought social and conservation problems due to the lack of ecological information and/or management tools. For the loggerhead turtle (Caretta caretta), the GU is an important feeding area, so the interaction with anglers is frequent. In this sense, some events of high loggerhead mortality have resulted in restrictive fishing measures; nevertheless, alternative hypotheses should be explored to explain this fact better. With the purpose of not only knowing the ecosystem ecological attributes but also obtaining specific ecological facts of the loggerhead turtle – as instantaneous total mortality – this study proposes Ecopath with Ecosim (EwE) model by calculating Allen's approximation of production to biomass ratio (P/B). Using the thermoregulation theory of ectotherms and this baseline model, the scenarios were run in Ecosim combining two forcing factors (FF): sea surface temperature (SST) and different fishing effort (F) values. All Ecosim scenarios were run over 30 simulated years taking the (P/B) values of the loggerhead turtle. According to the results in this study, the model allowed us to obtain specific ecological attributes for C. caretta, particularly for the P/B estimates in different simulation scenarios, which showed that colder sea surface temperature increases loggerhead mortality. All the information combined provided a better panorama to understand the role this turtle has within the Biological Action Center of the GU system and its interaction with other activities developed on site, such as fishing.