Fishermen may be slaughtering up to 15,000 dolphins annually in Peru's waters, using the marine mammals' fat and meat as bait for sharks, whose fins are prized in Asia, the Mundo Azul environmental group said.

"Between 5,000 and 15,000 (dolphins are killed for bait) ... We have to add to them about 1,000 or 2,000 dolphins that are used for illegal meat consumption. The same fleet that uses them as bait also supplies the illegal (meat) market," Mundo Azul executive director Stefan Austermuhle told Efe.

A video shot by Mundo Azul and provided to Efe shows the cruel treatment dolphins are subjected to by fishermen, who operate without fear of a crackdown by authorities even though the marine mammals have been a protected species since 1996 in Peru.

Peruvian law bans dolphin fishing, as well as the processing and sale of meat or parts from the marine mammals.

The video shows fishermen harpooning a dolphin and hauling it aboard their boat while the animal flaps around.

The dolphin is beaten repeatedly with a club, cut and left to bleed to death.

Fishermen butcher the dolphin, separating the meat, fat and internal organs in containers, and later tossing what is left of the animal into the sea.

Mundo Azul members posing as documentary filmmakers sailed with the fishermen in May and September, spending 24 days at sea on the second voyage, Austermuhle said.

Fishermen told the environmentalists that blue sharks are attracted to dolphin meat, which is added to bait composed of fish and mollusks, Austermuhle said. EFE