Response of cetaceans to changes in their prey availability and environmental conditions

Student: 
Andrea Fariñas

The Celtic Sea Herring stock declined in 2013 and has not yet recovered. Herring and sprat are the most important species for the Irish pelagic fisheries and their stocks are concentrated around the south of Ireland. Baleen whales and common dolphins feed in this area on herring and sprat, among other prey.
The associated changes in the ecosystem and the response of cetaceans to the herring decline are still unknown. This study aims to address these concerns though first characterising the spatio-temporal patterns of abundance in the studied species (herring, sprat, common dolphins, baleen whales) and the environmental conditions (sea surface temperature and primary production proxies), secondly comparing these patterns before and since 2013 and, lastly, modelling the effects of these ecosystem components on cetaceans using Hurdle Generalised Additive Models.
Changes in the herring stock distribution, sprat abundance and environmental conditions were observed since 2013. Common dolphin relative abundance and distribution were influenced by environmental variables and herring, possibly preferring small individuals. Associations with prey species and hence, presumably, prey preference, seemed to differ among whale species, although further research is required to confirm this. Overall, this study emphasises the importance of Ecosystem-Based Management approaches considering the relationships among ecosystem components.