The grey seal is easy to identify, particular the male with a head looking like a horse. At birth the pups have a white (greyish), long-haired coat called lanugo. The birth weight is approximately 15 kg. During a two-week sucling period they increase their body mass to 40–60 kg.
The grey seals occur in colonies of various densities on the most offshore islands along the Norwegian coast from Rogaland to Finnmark. In the area from Froan in Sør-Trøndelag to Lofoten in Nordland, the breeding season is in mid Sepember to late October, while the pupping period in Rogaland, Troms and Finnmark is from mid November to mid December.
The grey seal is managed separately in three areas: Lista–Stad, Stad–Lofoten and Vesterålen–Varanger. Recent DNA studies of grey seals show a strong genetic differentiation between the three current management areas
The grey seal is a main host for parasitic worms occurring in fish species, and can interact significantly with fisheries and fish farms.