Research Document - 2010/133
Spatial overlap between a pinniped predator, the grey seal and several prey species on the Scotian Shelf (NAFO zone 4VsW)
By V. Harvey and M.O. Hammill
Abstract
The spatial overlap between 56 grey seals equipped with satellite transmitters and 11 fish species including cod on the Scotian Shelf (4VsW) was examined. Foraging patches of males and females overlapped considerably. Seals remained within their foraging patches for an average of 6.1±0,53 days. Patches were located on average at 97.3±4.6 km from Sable Island. Foraging patch area was larger during the 1990s (493.5±151.3 km²) than during the 2000s (225.4±41.3 km²). The probability of a foraging patch occurring varied with a combination of fish abundance and distance from Sable Island. Overall, the probability of occurrence of a foraging patch decreased with distance from Sable Island. Species selected at close proximity to Sable Island differed from those that overlap with the foraging patches of seals further offshore. In July, female grey seals showed some selectivity for medium size cod, and small silver hake, while no selectivity for cod was observed among males. During March, males showed selectivity for medium (pre-2000) and for large (decade=2000’s) cod. While the foraging patches of males overlapped with large haddock and large cod at close proximity to Sable Island, this association declined gradually with distance from the Island
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