In 1972, the United States Congress enacted a law to protect dolphins and other marine mammals. This act, called the Marine Mammal Protection Act ("MMPA"), was passed because citizens and environmental groups were concerned that certain marine mammals were in danger of extinction or depletion due to human activity. [Congress sought to achieve a "balance" in enacting the MMPA.] In particular, Congress was concerned with the high dolphin mortality rates caused by the tuna fishing industry.
Almost all tuna sold in cans is caught in nets with a method called "purse seining." Seining is a very technical procedure which involves circling schools of fish with large nets (up to a mile long and 600 feet deep) and "pursing" the bottom of the net with a huge drawstring to trap the fish. For reasons that are still not understood, tuna and dolphins swim together in large numbers in the eastern tropical Pacific Ocean ("ETP"). Dolphins die in the nets because they are unwilling or unable to jump over the closing net and escape. Between 1959, when purse seine nets became widely used, and 1972, tuna fishermen in the ETP killed millions of dolphins. [Congress initially heard testimony that 200-400,000 dolphins were being killed per year due to purse seining.]
In passing the MMPA, Congress found that certain species of marine mammals, are, or may be, in danger of extinction and that such species should not be permitted to diminish to a point where it could damage the ecosystem of which they are a part. The MMPA established a prohibition, with certain exceptions, on the "taking" (defined in the law to mean "to harass, hunt, capture, or kill, or attempt to harass, hunt or kill) of marine mammals in the United States, and on the importing of marine mammals and marine mammal products into the Untied States. [The case of U.S. v. Hayashi further delineated the term.]
Congress has amended or changed the MMPA many times since 1972. [Significant amendments occurred in 1981, 1984, and 1988]. The agency responsible for implementing the MMPA, the National Marine Fisheries Service ("NMFS"), has issued a number of regulations as well. Finally, the courts have addressed many issues and controversies under the act. [Cases have dealt with feeding wild dolphins and releasing captive dolphins among other things.] These amendments, regulations, and court decisions have tried to strike a balance between protecting dolphins, and other marine mammals, and the security of jobs and livelihood of the commercial fishing industry.
For more on dolphins, see Detailed Discussion.