Study shows rise in Cornwall's dolphin, whale and porpoise deaths

July 7, 2008

Four weeks on from the shocking incident that led to the death of 26 dolphins near Falmouth, research sheds new light on the extent of the problems facing Cornwall's marine mammals.

A study by the University of Exeter and Cornwall Wildlife Trust, published in the journal Biodiversity and Conservation, has revealed a disturbing rise in the number of whales, dolphins and porpoises found dead on Cornish beaches. The frequency of these mammals, collectively known as cetaceans, found stranded on beaches in Cornwall has increased with a sharp rise in the last eight years. After analysing nearly 100 years of data, the researchers believe this could, in part, be due to more intensive fishing.

The research team analysed records of cetacean strandings from 1911 to 2006 from around Cornwall's north and south coasts and the Isles of Scilly. They found a marked increase from the early 1980s, with common dolphins and harbour porpoises being the worst-affected species. In total, fewer than 50 cetacean strandings a year occurred in Cornwall in the 1980s but numbers since 2000 have ranged from 100 to 250 per annum. The south coast of Cornwall experienced the most strandings, particularly around Mount's Bay (Penzance) and two of South East Cornwall's most popular beaches - Looe Bay and Whitsand Bay.

The researchers analysed records of 2,257 cetaceans, 862 of which were common dolphins. They found that, since 1990, at least 61% of incidents in Cornwall are the result of fishing activity, with animals being caught up in nets in a phenomenon known as 'bycatch'. The seas around Cornwall are known to be a major hotspot for large scale fisheries, with many vessels coming from other EU nations.
They analysed data from a rigorous recording scheme, run by Cornwall Wildlife Trust's Marine Strandings Network, which is backed up by full veterinary autopsies as part of a national programme run by the Zoological Society of London and the Natural History Museum.

Dr Brendan Godley of the University of Exeter's Cornwall Campus said: "Many people were shocked by the recent graphic images of the mass dolphin strandings in Cornwall; the cause of which is still a matter of conjecture. We feel that the important message is that strandings have increased in recent years and that the majority are attributable to bycatch in marine fisheries. This is clearly a major issue that needs to be addressed by all stakeholders from Government and the fishing industry in addition to conservation organisations."

The researchers note, however that their findings could, in part, suggest that there are more cetaceans now living off our coastline, as a result of climate change bringing some animals further north.

Joana Doyle, Marine Conservation Officer for Cornwall Wildlife Trust says: "There are several things we need to do in order to safeguard the future of Cornwall's cetaceans. These include establishing a network of Marine Conservation Zones around our coast to protect the species and the habitats they depend on, working closely with the fisheries to develop and test bycatch mitigation measures and pushing for an EU wide ban of pair-trawling for seabass. The strandings and sightings data collected by Cornwall Wildlife Trust is incredibly important for monitoring the status of our cetacean species off the Cornish coast."

Source: University of Exeter