The International Dolphin Conservation Program Act (IDCPA) was a 1997 amendment to the US Marine Mammal Protection Act. It is the U.S. implementation of the international Agreement on the International Dolphin Conservation Program, to which the U.S. is a signatory. Among other things, the IDCPA directed the National Marine Fisheries Service to conduct studies to determine "whether the intentional deployment on or encirclement of dolphins with purse seine nets is having a significant adverse impact on any depleted dolphin stock in the eastern tropical Pacific Ocean." The act required a preliminary report in 1999 and a final report in 2002. A series of reports and papers supported the final summary report.
Since 2002, scientists at the Southwest Fisheries Science Center have continued studies focused on the question of the impact of the fishery on dolphins. These further studies have included cruises to the Eastern Tropical Pacific and further analyses. The first question is whether the dolphin populations are recovering as expected. The reported kill has been reduced to such a low level (less than 0.1% for each dolphin stock) that it should have a negligible impact, and the dolphin populations should be recovering from the reduced levels due to earlier high bycatch. At this time, however, it does not appear that the dolphin populations are growing at rates that we would expect.
There are 3 hypotheses for the lack of recovery:
1. The fishery (the kill is underreported or negative effects of the fishery go beyond the direct kill)
2. Habitat (the ocean has changed negatively for these dolphins)
3. Other species (recovery might be prevented or delayed because of interactions with other species)