Large, mature yellowfin in the tropical eastern Pacific Ocean school together with dolphin pods. In the 1950s, fishermen discovered they could catch these yellowfin by setting their nets around the pods of dolphins. In the 1980s, when this became more widely publicized, fishermen changed their practices due to consumer pressure and began using large pieces of wood or other devices shaped like dolphins to lure tunas into their nets. Because there is still so much bycatch using these devices, many conservationists and fishermen feel this method of fishing for tuna is not the solution.
In 1990, the Dolphin Protection Consumer Information Act (DPCIA) prohibited labeling tuna cans "dolphin safe" if the tuna is harvested using methods harmful to dolphins. In a separate agreement called the Panama Declaration several Latin American nations agreed to hold the total annual dolphin mortality below 5,000 in exchange for the amendment of this U.S. dolphin-safe standard. The amendment allows fishermen to set nets on dolphins to catch larger, mature tuna that school under dolphins, and then back down the net to let the dolphins jump over and escape.
While this back-down technique appeared to be a viable solution, more recent research has shown this activity causes undue stress to dolphins that may affect their long-term survival. On average, a northeastern spinner dolphin is chased 11 times per year and caught three of those times. The research revealed some dolphins found dead in the nets died of heart lesions consistent with overexertion—other animals showed evidence of healed heart and muscle lesions, suggesting that heart and muscle damage is routine. Stress may suppress their immune function and reproductive fertility and cause some pregnant dolphins to abort their fetuses. In addition, any chase lasting more than 30 minutes results in dolphin calves becoming separated from their mothers, an experience most calves can't survive. Researchers concluded that the impact to dolphins is greater than first thought, a situation that requires more research. However, authorities amended the dolphin-safe standard to allow the use of the back-down technique if no dolphins were killed.
It’s important to note that while the dolphin-safe label has improved the impact of the fishery on dolphins, they’re not completely out of harm’s way. This is why even tuna labeled "dolphin-safe" is a good alternative but not a best choice. Canned tuna that’s troll or hook-and-line caught is a best choice.
For a list of sustainable tuna sources, please visit our Sustainable Seafood Sources section