for National Geographic News
At least 7.8 million sharks are killed off southern Africa each year by hooks intended for other animals, a new study says.
Accidentally caught animals, or bycatch, also include some 34,000 seabirds and 4,200 sea turtles every year off the west coasts of South Africa, Namibia, and Angola, according to the report, released last week by the conservation organizations WWF South Africa and BirdLife South Africa.
The animals get caught on baited hooks on longlines used by fishing boats targeting tuna and hake. The heavy fishing lines can trail for several miles behind a ship.
"The majority of albatross and sea turtle species and many shark species are listed as threatened with extinction by the IUCN (World Conservation Union), with fisheries impacts being cited as a major cause," said a WWF South Africa statement.
Marine experts say bycatch around the world has contributed to a serious decline in the population of some sharks, mammals, seabirds, turtles, and numerous other species.
"About a third of the fish that are caught [around the world] are discarded as bycatch," said Beth Babcock, an ocean scientist at the University of Miami in Florida. "That's just an incredible amount of fish that are killed and wasted without being food for anyone."
"You look at some of the threatened fish, and bycatch in fisheries is the main reason why they're threatened," Babcock added.
Different types of fishing practices tend to kill different species as bycatch, WWF says. Nets often kill dolphins and whales. Longline fishing kills sharks, birds, and turtles. Bottom-trawling scoops up sea stars (starfish) and other creatures living on the seafloor.
Shrimp fisheries have the highest level of bycatch, says the nonprofit environmental group Greenpeace. More than 80 percent of a catch may consist of marine species other than the shrimp being targeted, Greenpeace says.
According to some estimates, more than a hundred million sharks and rays may be caught and discarded every year. (Related: "Shark Declines Threaten Shellfish Stocks, Study Says" [March 29, 2007].)
"It has become increasingly apparent over the last several years that fisheries have dramatically reduced populations of top predators in many areas of the world, and sharks are particularly hard hit," said Mike Heithaus, a marine biology professor and shark expert at Florida International University in Miami. (Heithaus has received grants from the National Geographic Society, which owns National Geographic News.)
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