Economic Importance for Humans: Negative
Grey seals are widely believed by commercial fisherman to be a pest. They may remove fish from nets, become tangled in nets, damage traps, and feed on farmed fish. These seals are also hosts for a parasitic roundworm called codworm (Pseudoterranova decipiens), that infects cod and other commercially harvested fish.
There is some dispute about the large-scale impacts of grey seals on the Atlantic fisheries, but they are at least occasionally a problem in local situations.