Ecological factors affecting the whale shark occurrence in Djibouti and presence of contaminants in the trophic web

Djibouti is an important site where the whale shark (Rhincodon typus Smith 1828) regularly aggregates. Sharks gathering off the Djibouti coast are mostly juvenile males and target dense concentrations of zooplankton. However, only few studies has been carried out, leaving a knowledge gap on the main aspects of the whale shark ecology. Therefore, the main outcome of this study is to determine the environmental factors influencing the presence and distribution of this species in Djibouti. A robust understanding of the spatiotemporal distribution is required for developing successful management strategies for the whale shark protection in this area. Moreover, whale sharks may be potentially exposed to relatively high levels of contaminants in Djibouti since they aggregate along one of the world busiest shipping route. Although the massive release of pollutants in African marine ecosystems and the deleterious effects on biota and humans, at present almost nothing is known about the contamination status of the Gulf of Aden, including Djibouti. The scarcity of studies includes all trophic levels, therefore, with a bottom-up approach, starting from zooplankton to get to predatory shark species, this study aims to characterize the trophic chain from an ecotoxicology point of view. With global decline in shark numbers, evaluating the extent of contaminant exposure is an urgent aspect since anthropogenic pollution may exasperate the current situation. Furthermore, since elasmobranchs are component of the artisanal fishery in Djibouti, and seafood consumption is as an important source of contamination for humans, this study aims to estimate for the first time the exposure health risks derived from shark consumption.