Entanglement in marine debris has been internationally recognised as a potential threat to marine species since the 1984 International Workshop on the Fate and Impact of Marine Debris. In particular 56% of pinniped species have records of entanglement.
Average entanglement rates of grey seals Halichoerus grypus at a haul out site in North Cornwall range from 2-5% of sightings. Entanglement rates an order of magnitude lower than this have been implicated in population declines of other pinniped species.
Whilst the focus of many studies has been the population level effects on species, a long-term photo identification study of grey seals Halichoerus grypus visiting this haul out site found that even seriously impacted seals are capable of surviving for up to seven years. This raises welfare concerns for the affected animals that are spending months to years of time with deep constrictions and persistent open wounds.