It’s a practice that animal conservation groups say is widespread in the South American country.
We need to warn you that this report by CNN’s Rafael Romo can be too graphic for some viewers.
Off the Peruvian pacific coast in South America, a fishing vessel is sailing in rough waters. Right under the ship's bow, several dolphins swim back and forth while a menace lurks on the surface, just a few meters above.
One of the dolphins has been harpooned and is now being hauled onto the ship, bleeding profusely. What happens next is hard to watch. Fishermen begin to cut up the dolphin while the animal is still alive.
"It's then flensed, which is the technical term for the skin of the dolphin being peeled of its back. And it's cut to be used as fish bait."
Jim Wickens, a journalist with the London-based ecologist film unit, witnessed the scene along with a photographer from Argentina who recorded the gruesome images on video.
The dolphins are chopped up to be used as bait for sharks.
"In recent years in Peru there's been an upsurge in the targeting of sharks. The shark meat is predominantly consumed within Peru but the fins we're told are being exported to the Far East for use as shark fin soup."
"It's very hard to know how many dolphins are being killed worldwide, Rafael, because it simply happens out of sight and out of mind. Conservation experts Mundo Azul in Peru estimate over 10,000 are being killed every year in Peruvian waters alone."
Peruvian officials say the practice has been illegal since 1996 and are considering banning shark fishing to discourage the use of dolphins as bait.
"We're evaluating and if we find out that this is a widespread practice and the fishing of one species is affecting another, then we're going to take drastic measures. That means using tool at our disposal including banning the fishing of certain species as well as the sale of others."
Dolphin hunting has financial incentives. NGOs estimate every fishing expedition nets the fishermen about 22,000 dollars.
"It's a conservation car crash: one apex predator being taken out of the ecosystem, being chopped up and fed to catch another. Whichever way you look at it, it’s bad news for the ocean."
The London-based ecologist film unit in cooperation with the Pulitzer center for crisis reporting collaborated with the Peruvian animal conservation NGO known as Mundo Azul to obtain the video. The fishermen knew the foreigners were journalists and allowed them on board for a week in exchange for fuel money and the protection of their anonymity, although they didn't know the full scope of their investigation.
Conservation groups say the practice is not unique to Peru. They've also received reports of dolphin fishing for shark bait in Asia, where shark fin soup is considered a delicacy.