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

Abstract

1. 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. 2. 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. 3. Behavioural observations were conducted along the north-western coast of Spain, an area affected by intensive human activities, particularly the shellfish aquaculture industry. 4.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 ofenvironmental 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). 6. 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.

A global review of protected species interactions with marine aquaculture

“…Seal abundance was the same at sites with and without mussel farms, and no negative interactions were reported. Along the northwestern coast of Spain, mussel farms influence habitat uses and foraging behaviour of bottlenose dolphins 91,92 . The shellfish culture method may impact animals differently due to the gear configurations and materials used.…”

“…Along the northwestern coast of Spain, mussel farms influence habitat uses and foraging behaviour of bottlenose dolphins. 91,92 The shellfish culture method may impact animals differently due to the gear configurations and materials used.…”

Vulnerability of a top marine predator in one of the world’s most impacted marine environments (Arabian Gulf)

“…When dolphins were sighted, searching effort ceased and the vessel slowly maneuvered toward them to minimize possible disturbance during approach. A group of bottlenose dolphins was de ned as one or more individuals observed within a 100-m radius and, if more than one, interacting with each other and performing the same behavioural activity (Methion and Díaz López 2019). At least two observers with digital SLR cameras equipped with telephoto lenses attempted to photograph both sides of the dorsal n of each dolphin of the group.…”

“…Bottlenose dolphins (Tursiops spp. ), despite being widely considered some of the most adaptable of the world's cetaceans, are highly susceptible to environmental changes (Bejder et al 2006;Sprogis et al 2018;Díaz López 2019;Methion and Díaz López 2019). Due to their inshore distribution and life history characteristics (i.e., relatively large size, slow growth, late maturation, long gestation period, single births at a time, and long calving interval), bottlenose dolphins are vulnerable to a range of anthropogenic impacts such as habitat modi cation, over shing, noise and chemical pollution, bycatch, and boat strikes (Díaz López 2006;Wang and Yang 2009).…”

Effects of pollution on marine organisms

“…A meta‐analysis of the impacts of marine and freshwater aquaculture found that aquaculture facilities attract a variety of species, particularly wild fish, which were found to be on average 1.2× larger and 1.7× heavier than fish from reference sites; marine mammals showed no consistent response to the presence of aquaculture facilities, though pinnipeds were found to experience higher mortality from aquaculture facilities due to culling and entanglement (Barrett, Swearer, & Dempster, 2019). Bottlenose dolphins ( Tursiops truncates ) off the northwestern coast of Spain, however, were found to forage predominantly inside shellfish farming areas, with such behavior correlated to both environmental conditions (sea surface temperature and time of day) and the presence of shellfish farms (Methion & Lopez, 2019).…”