So many dead dolphins are washed up on the Atlantic coast of France that marine biologists are deeply concerned about the survival of local populations of marine mammals.
The vast majority of the dead dolphins drowned in the trawls of fishing vessels. Carcass research often identifies bone fractures, tail and fin fractures and deep cuts caused by the nets. Some cadavers were further damaged by fishermen who removed them from the nets.
“We have reached a mortality rate that threatens the survival of the dolphin population in the Bay of Gascony,” said Marine biologist in Brittany Morgane Perri. “In the last three years, we’ve had a four-month period each winter with more than 1,000 dead dolphins and porpoises.”
“Actual number of dead dolphins up to ten times greater”
Common dolphins are the hardest hit. Scientists believe that the dolphin carcasses found on beaches are only a small part of the total number of dolphins killed in fishing nets off the French coast. The actual number of dead dolphins is five to ten times greater, they estimate.
Dolphins have been entangled in nets on Europe’s west coasts for decades, but marine biologists say the number of dead animals has been growing in recent years due to changed fishing techniques. In particular, fishing vessels fishing for sea bass in pairs with trawls would kill many dolphins.
French law requires that fishermen who find cetaceans in their by-catch report it. According to Perri, this rarely happens.
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Jumping dolphins at Cancale, France. (Photo: Reuters)
Dolphins are extra vulnerable
Dolphins reproduce slowly, making their populations extra vulnerable if their numbers drop sharply. Helene Peltier, a researcher at the Pelagis Observatory in La Rochelle, said that models now show that the dolphin populations are stable. “But once you see a decrease there, it’s actually too late.”
Activist organization Sea Shepherd wants to prohibit trawl fishing in sea bass spawning grounds and increase fisheries surveillance. Some fishermen experiment with sound signals to deter dolphins.
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