Distribution of bottlenose dolphin in Galician region (NW Spain), the impact of mussel farming on species

The spatial and seasonal distribution of common bottlenose dolphin and possible links with environmental conditions were studied at the Galician continental shelf. Data was collected between June 2019 and July 2019 during opportunistic surveys onboard fishing boats. Modelling results indicated that the number of common dolphin sightings per unit effort was higher further in the outer ria in shallow waters. Shellfish farming is an expanding segment of marine aquaculture, but the impact of this industry on bottlenose dolphins is only beginning to be considered. Over a period of 1 month spent in the field, 11 daily boat surveys and 53 common bottlenose dolphin encounters were done. Results of this research confirm that bottlenose dolphins prefer areas relating to such factors as sea surface temperature and prey availability. Moreover, there is an overlap between distribution of the dolphins and mussel production as mussel farming rafts cover 17% of Ria de Arousa. However, it was revealed that bottlenose dolphins are not avoiding the area of mussel production and can be outside the mussel rafts the same amount of time as inside. This research provides new insight into the mussel farming impact on the common bottlenose dolphins in Galician waters showing that this limiting factor is not major in the area.