Southwest Region - Tuna Dolphin Interaction
In the eastern tropical Pacific Ocean (ETP) west of Mexico and Central America, large yellowfin tuna swim with several species of dolphins. This ecological association of tuna and dolphins is not clearly understood, but it has had two important consequences:
(1) it has helped create a successful tuna fishery, and
In one type of fishing method, fishermen intentionally capture both tuna and dolphins in a large purse seine, and then use various procedures to release the dolphins from the net. In the mid-1960s widespread awareness of the degree of dolphin mortality in the ETP tuna fishery occurred. Dolphin mortality has since decreased from almost 13 dolphins per set to an average of 0.1 dolphins per set over the last 20 years. Although this decline in dolphin mortality has been dramatic, ETP dolphin stocks are not recovering at the expected rate. Several hypotheses have been offered to explain this, including indirect effects such as ecosystem or environmental changes, and direct effects of repeated chasing and encirclement (internal injuries, stress, and hypothermia). Evaluating these hypotheses and estimating the impact of the fishery are the focus of ongoing research (ETP Cetacean Assessment).
Current Management Actions
A 2004 decision by the U.S. District Court set aside the final finding made by NMFS that the fishery had no adverse impact on dolphin stocks in the ETP. The court ordered that the "dolphin-safe" labeling standard for yellowfin tuna harvested by large purse seine vessels in the ETP would be governed by the Dolphin Protection Consumer Information Act. A federal appeal failed in 2007, and "dolphin-safe" in the United States continues to pertain to tunacaught on a trip in which (1) the purse seine was never intentionally deployed on or to encircle dolphins, and (2) no dolphins were killed or seriously injured during the sets in which the tunawere caught. The Department of Commerce is reviewing the court’s most recent decision and considering next steps.