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Marine Ecology Progress Series

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MEPS 462:273-286 (2012)  -  DOI:

Winter foraging by a top predator, the grey seal Halichoerus grypus, in relation to the distribution of prey

V. Harvey1, M. O. Hammill1,*, D. P. Swain2, G. A. Breed3, C. Lydersen4, K. M. Kovacs4

1Maurice Lamontagne Institute, Mont-Joli, Quebec G5H 3Z4, Canada
2Gulf Fisheries Centre, Moncton, New Brunswick E1C 9B6, Canada
3UC Santa Cruz, Long Marine Lab, Santa Cruz, California 95060, USA
4Norwegian Polar Institute, Tromsø 9296, Norway

ABSTRACT: Identifying foraging areas of individuals and correlating them with potential food resources allows for a better understanding of predator–prey relationships. Herein, we examine whether grey seal movements were associated with overwintering concentrations of several commercial fish species in the Cabot Strait, Atlantic Canada, using data from satellite transmitters deployed on grey seals (between 1993 and 2005) and winter bottom-trawl survey data (1994 to 1997). The distribution of searching effort by male grey seals varied throughout the winter. In early winter, males concentrated their movements around St. Paul’s Island. In late winter, they were found to the southeast of this area, where females also occurred. The fish community differed between apparent foraging and non-foraging areas. Densities of small plaice, hake and redfish, large herring and cod of all sizes were relatively high in the male grey seal foraging zones; female foraging zones were characterized by higher densities of small plaice and redfish and large cod. Areas where grey seal foraging was not concentrated were characterized by high densities of medium and large redfish as well as large turbot and witch flounder. Diet samples are needed to determine whether grey seals are feeding on the fish groups that distinguish foraging from non-foraging areas or alternatively on other prey that occur in the same areas.

KEY WORDS: Marine predator · Foraging areas · Cod · Spatial overlap · First-passage time · Groundfish · Gulf of St. Lawrence

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Cite this article as: Harvey V, Hammill MO, Swain DP, Breed GA, Lydersen C, Kovacs KM (2012) Winter foraging by a top predator, the grey seal Halichoerus grypus, in relation to the distribution of prey. Mar Ecol Prog Ser 462:273-286.

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