News Main
Animals
Archaeology
Dinosaurs
Earth
History
Human Animal
Space
Tech

Fishing Nets Entangling Fewer Dolphins

Jessica Marshall, Discovery News

The fact that recovery has been slow may indicate that even with new measures in place, dolphins continue to suffer in other ways from the tuna fishery.

Yellowfin tuna swim with dolphins, so fishermen often use dolphin sightings to locate tuna. Then they chase and surround the dolphins with nets to capture the tuna beneath.

Previously, they would scoop up the dolphins along with the fish, but since the regulations took hold they drive their boat in reverse after surrounding the dolphins, to force the nets beneath the dolphins at the water's surface. This approach, known as backdown, lets the dolphins out while still trapping the tuna inside.

But some other aspects of the chase may be slowing recovery.

"Even though the vast majority of dolphins caught in nets are now released alive, scientists believe that repeated chases and separation of mothers from calves continue to stress these dolphins and affect their ability to recover to pre-fishery levels," said Vicki Cornish of the Ocean Conservancy in Washington, D.C.

In the United States, tuna cannot be labeled "dolphin safe" if dolphins are chased at all, even if the backdown method is used. But one of the main alternative methods -- using "fish aggregation devices" that, like dolphins, lure tuna to school beneath -- is not without problems, Cornish said.

"The problem with fish aggregation devices is there's a higher bycatch on turtles and sharks and smaller tuna."

"It's encouraging to see that maybe the dolphin stocks are starting to bounce back," she said. "We need to continue to find fishing techniques that do not affect other species."

Southwest Fisheries Science Center

How Stuff Works: Dolphins

Planet Green

Discovery Earth Live