Natural and anthropogenic drivers of foraging behaviour in bottlenose dolphins: Influence of shellfish aquaculture

In the coastal environment, marine mammals are exposed to one of the fastest growing food production sectors; namely, the shellfish farming industry. Identification of critical habitats, such as foraging grounds in highly human-impacted areas, is essential to species conservation. Therefore, understanding the variables that influence a species' foraging behaviour is important for their conservation, especially for long-lived mammals such as cetaceans. The aims of this study were (a) to identify and quantify the environmental and anthropogenic drivers of wild bottlenose dolphin (Tursiops truncatus) foraging behaviour, and (b) to investigate whether the shellfish farming industry influences the behaviour of this species. Behavioural observations were conducted along the north-western coast of Spain, an area affected by intensive human activities, particularly the shellfish aquaculture industry. A multi-modelling approach highlighted the importance of shellfish farm areas as a foraging ground for bottlenose dolphins. Dolphins were predicted to be more likely found foraging inside shellfish farm areas than outside (57% vs. 43%). Variability in bottlenose dolphin behaviour is likely a result of the interactions of environmental and anthropogenic drivers with prey availability and the physiological needs of the dolphins. Although shellfish farm areas provide high prey density for dolphins, they can also pose threats in a number of ways (i.e. collisions with vessels, entanglement with ropes, habitat loss, noise and water pollution). From a conservation perspective, aquaculture management should consider the presence of dolphins foraging and minimize the associated risks that this industry may pose to these coastal cetaceans.