Fine-scale spatial association between baleen whales and forage fish in the Celtic Sea

• Main Authors: Volkenandt, Mareike, O'Connor, Ian, Guarini, Jean-Marc, Berrow, Simon, O'Donnell, Ciaran
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2015
• Subjects: Balaenoptera acutorostrata; Balaenoptera physalus; baleen whale; baleen whales; Megaptera novaeangliae
• Online Access: http://hdl.handle.net/1807/70981; http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2015-0073

Baleen whales can be regularly observed in the Celtic Sea, however little is known about their local foraging behaviour. The study objective was to determine whether or not baleen whales selectively prey upon particular forage fish species or, on the contrary, is predation on the Celtic Sea plateau driven by random encounters between prey and predator? Concurrent sighting surveys for fin, minke and humpback whales (Balaenoptera physalus, Balaenoptera acutorostrata and Megaptera novaeangliae) were carried out simultaneously from 2007 to 2013 during dedicated fisheries acoustic surveys assessing the abundance and distribution of forage fish. Probabilities of spatial overlap between baleen whales and forage fish were analysed and compared to the probability of a random encounter. For estimations of foraging threshold and prey selectivity, average fish biomass and fish length were calculated when baleen whales and forage fish co-occurred. Whales were dominantly observed in areas with herring (Clupea harengus) and sprat (Sprattus sprattus), while areas with mackerel (Scomber scombrus) were not targeted. A prey detection range of up to 8 km was found, which enables baleen whales to track their prey to minimise search effort. Fish densities within the defined foraging distance ranged from 0.001 to 3 kg m-2 and were correlated to total fish abundance. No prey size selectivity according to fish length was found. By linking baleen whale distribution to high-density herring and sprat areas it was possible to identify the Celtic Sea as a prey hot spot for baleen whales during autumn. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.