The environmentally devastating practices, including practices that can lead to dolphin mortality, of these companies are not "sustainable" or "dolphin-safe." These claims are deceptive and constitute false advertising to consumers, who rely on the accuracy of such representations to make informed purchasing decisions.
Bumble Bee and Chicken of the Sea claim to be "100% dolphin-safe," and all three of the suppliers state they will not purchase tuna caught in association with dolphins—a significant concern because tuna often swim together with dolphins. Dolphins can be traumatized, netted, injured, and killed by typical tuna fishing practices, including the use of giant "purse seine" nets, which capture dolphins along with tuna. Yet while approximately half of tuna consumers believe the dolphin-safe label means no dolphins died for the tuna in their can, the number of dolphins killed or injured by "certified" dolphin-safe tuna fishing methods in reality could number in the thousands every year. According to Greenpeace, around 300,000 cetaceans—whales, dolphins, and porpoises—die as bycatch each year.
Meanwhile, on their packaging and their websites, the top three tuna suppliers all outline their commitment to "sustainable" fishing practices—ones that won't deplete resources or harm the natural cycles of tuna or other marine life. However, the longlines and purse seine nets used to catch approximately 75% of the world's tuna—including tuna sold by Bumble Bee, Chicken of the Sea, and StarKist—kill millions of non-target marine animals as "bycatch" every year, including sharks, sea turtles, dolphins, whales, and even sea birds. Some of these populations have been so decimated by commercial fishing that they are now critically endangered.
Longline fishing and purse seine fishing are not "sustainable." These companies need to stop using greenwashing to deceive well-meaning consumers. If you agree, boycott all three!
Since practices required for 'dolphin-safe' certification don't provide a 100% guarantee that dolphins are not harmed, the best way to be fully assured of dolphin-safety is simply not to eat tuna—this is best for the tuna, as well! However, some fishing practices—like use of giant purse seine nets—are clearly more environmentally devastating, and dangerous to dolphins, than others. If you choose to eat tuna, you can contact tuna companies to find out if their suppliers use purse seine nets.
 GREENPEACE, supra note 18.