Dead dolphins are washing up on France’s Atlantic coast in such large numbers that regional populations of the animals are at jeopardy, marine biologists state.
The overwhelming majority died in the nets of fishing trawlers. Post mortems frequently reveal cracks, broken tails and flippers and extensive cuts cut into their skin by the nets. Some have been damaged as fishermen free their bodies, Reuters reported.
“We’re reaching mortality rates that threaten the survival of the dolphin population in the Bay of Gascony,” said Morgane Perri, a marine biologist in Brittany, western France.
“For the last three years, we’ve seen more than 1,000 deaths (of dolphins and porpoises) over four months each winter.”
Common dolphins are the hardest hit. Experts assume those discovered on shores represent a small portion of the total number falling in fishing nets off the coast of France. The actual number is expected to be five to 10 times higher, they estimate.
Dolphins have for decades been trapped in fishing nets in the Atlantic waters off Western Europe. But marine scientists maintain the spike in numbers in recent years is a consequence of shifting fishing practices, and in special, the fishing boats that trawl in pairs for sea bass.
French law obliges fishermen to maintain all cetacean by-catch, but Perri said this seldom occurred.
The National Committee of Maritime Fishermen did not directly reply to a request for an explanation.
The delayed breeding rates of dolphins, mammals that demand to surface to breathe, indicates they are especially vulnerable to sharp falls in numbers, according to the Pelagis Observatory in La Rochelle.
Population models show numbers are stable, said Helene Peltier, a researcher at the observatory. “But once you see the decline, it’s too late.”
Activist group Sea Shepherd wants trawlers to be banned from fishing in sea bass spawning grounds and better monitoring of fisheries. Acoustic ‘pingers’ designed to repel dolphins are also being trialled on some fishing boats.
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