Research Document - 2011/026

Historical Grey Seal Abundance and Changes in the Abundance of Grey Seal Predators in the Northwest Atlantic

By W.D. Bowen

Abstract

Grey seals have inhabited the north-western Atlantic for millennia. Estimates of grey seal abundance prior to the 1960s are vague, but clearly indicate that the species was considered rare during much of the early part of that century. Grey seals were once abundant enough to be hunted by indigenous tribes and by early European explorers. Although abundant enough to hunt, we have little idea of historical population size. Nevertheless, the current size of the grey seal population is the highest in the last century. Hunting can account for their rarity, but why have they increased so dramatically? A number of hypotheses have been advanced to account for the rapid growth, including release from predation by sharks and killer whales, reduced incidental bounty kill, increased ice-breeding habitat for pup rearing, and changes in the ecosystem favouring seals. Although none of these hypotheses can be completely discounted, reduce mortality in the bounty, increased breeding habitat and greater food availability must have all played a role.

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