A preliminary habitat suitability model for oceanic whitetip shark in the western Indian ocean
Understanding the temporal, spatial and environmental factors influencing species distributions is essential to minimize the interactions of vulnerable species with fisheries and can be used to identify areas of high bycatch rates and their environmental conditions. Classified as critically endangered by the International Union for the Conservation of Nature, the oceanic whitetip shark (Carcharhinus longimanus) is the second main shark species incidentally caught by the tropical tuna purse seine fishery in the western Indian Ocean. In this study, we used the European Union purse seine fishery observer data (2010-2020) and generalized additive models to develop a habitat suitability model for juvenile oceanic whitetip shark in the western Indian Ocean. Sea surface temperature was the main environmental driver suggesting a higher probability of occurrence of this shark with decreasing temperatures. The type of fishing operation also was an important predictor explaining its occurrence, suggesting a higher probability of incidentally catching this species when using fish aggregating devices as set type. Moreover, predictive maps of habitat suitability suggested the area offshore of Kenya and Somalia are an important hotspot with higher probabilities of incidentally catching this species during the summer monsoon (June to September) when upwelling takes place. The habitat suitability models developed here could be used to inform the design and testing of potential time-area closures in the Kenya-Somalia basin with the objective of minimizing the bycatch of this critically endangered species with the least possible impact on fishing operations and fishery yields of target tunas.