The intentional targeting of tuna-dolphin associations is a practice unique to the Eastern Pacific Ocean. In this region, purse-seine fishers capitalize on the natural tendency of yellowfin tuna to school beneath herds of dolphins. By setting their nets around these mixed groups, fishers are able to maximize their yellowfin yields.
While dolphin mortality was initially very high, the Inter-American Tropical Tuna Commission (IATTC) estimates that deaths have declined by 98% since the late 1980s. This significant reduction followed the collaborative development of “back-down” techniques by fishers and scientists, which allow dolphins to be released alive while the tuna are retained.
Despite these technical successes, the practice remains controversial:
• Post-Release Stress: Some scientists argue that unquantified mortality occurs after the dolphins are freed, triggered by extreme stress and the accidental separation of calves from their mothers.
• Outdated Data: Fishery-independent surveys from 2008 suggested that most regional dolphin populations were stable or increasing. However, because the last comprehensive survey was conducted in 2006, there is significant uncertainty regarding the current status of these cetacean populations.
On a broader ecological note, the incidental catch (bycatch) of other non-target species in these specific dolphin-associated operations remains remarkably low.