96011: Dolphin Protection and Tuna Seining
Updated March 4, 1997
Eugene H. Buck Environment and Natural Resources Policy Division
Schools of yellowfin tuna associate with dolphins in the eastern tropical Pacific (ETP) Ocean. U.S. fishermen began to exploit this resource in the late 1950s by encircling the dolphin schools with large purse seine nets to capture the yellowfin tuna swimming beneath the dolphins.
Despite efforts to release the entrapped dolphins (which were of no commercial value to the U.S. fishermen) while landing the tuna, dolphins became entangled in the nets and drowned. By the early 1970s, as many as 300,000 or more dolphins were estimated to have been drowned each year by U.S. tuna seiners fishing in the ETP.
From its inception in 1972, one of the goals of the Marine Mammal Protection Act (MMPA) was to reduce the incidental mortality of dolphins in the ETP tuna fishery. Strict regulations promulgated under MMPA authority set standards for tuna seining and motivated technological improvements that substantially reduced dolphin mortalities in this fishery -- by 1977, annual dolphin mortality caused by U.S. tuna seiners had declined to about 25,450 animals. Despite the extensive mortalities, no ETP dolphin population has been listed as endangered or threatened under the U.S. Endangered Species Act. However, two ETP dolphin stocks have been listed as depleted under the MMPA.
The ETP purse seine fishery was dominated by U.S. vessels through the 1960s and into the 1970s. By the 1980s, the U.S. fleet was declining, and more foreign vessels were entering the fishery. With this shift, total dolphin mortality began to increase again until more than 100,000 dolphins were killed by foreign tuna purse seine vessels in 1986. In April 1990, the three largest U.S. tuna processors responded to concerns over dolphin mortality by announcing that they would no longer purchase tuna caught in association with dolphins. This action caused many U.S. tuna seiners in the ETP to relocate to the western Pacific. Congress responded by enacting the Dolphin Protection Consumer Information Act to set standards for labeling tuna as "dolphin-safe," and the International Dolphin Conservation Act of 1992 to prohibit the sale, purchase, transport, or shipment in the United States of any tuna that was not dolphin-safe after June 1, 1994.
In response, foreign nations strengthened their programs for protecting dolphins during tuna seining through the non-binding International Dolphin Conservation Program developed by the Inter-American Tropical Tuna Commission. However, foreign nations barred from the U.S. tuna market became increasingly vocal that the United States should recognize their success in reducing dolphin mortalities by reopening the U.S. market to their tuna.
A Declaration of Panama was signed by 12 nations including the United States in October 1995, agreeing to modify U.S. law in exchange for binding commitments for further progress in dolphin protection. Four bills -- H.R. 2823, H.R. 2856, S. 1420, and S. 1460 -- were introduced in the 104th Congress to implement the Declaration of Panama. However, differences exist on the details of how U.S. law should be changed, particularly whether the definition of "dolphin-safe" tuna should be modified.
When the 104th Congress adjourned, the House had passed H.R. 2823, while the Senate had reported S. 1420. This issue will be taken up in the 105th Congress -- H.R. 408/S. 39 have been introduced.
MOST RECENT DEVELOPMENTS
The 104th Congress adjourned without taking final action on this issue. In the 104th Congress, H.R. 2823 was passed by the House, while S. 1420 was reported by the Senate Committee on Commerce, Science, and Transportation. In the 105th Congress, H.R. 408 was introduced in the House on Jan. 9, 1997, while S. 39 was introduced in the Senate on Jan. 21, 1997. (For daily or weekly summary updates providing more current information on marine and freshwater fisheries and marine mammal issues, send an e-mail message to email@example.com requesting to be added to the summary distribution list.)
BACKGROUND AND ANALYSIS
Tuna in the Eastern Tropical Pacific
In 1949, two bilateral Conventions were concluded to coordinate and manage expanding U.S. interests in tuna harvests in the eastern tropical Pacific (ETP) Ocean, a 20 million square mile area off the coast of Latin America westward to Hawaii. The United States signed a Convention with the Republic of Costa Rica for the Establishment of an Inter- American Tropical Tuna Commission (IATTC) and a Convention with Mexico for the Establishment of an International Commission for the Scientific Investigation of Tuna. In 1950, these agreements entered into force and were implemented domestically by the Tunas Convention Act of 1950. The IATTC was to carry out research on tuna and other fish taken by tuna vessels and to make recommendations for actions to maintain populations of these fish. In subsequent years, additional ETP tuna fishing nations became parties to the IATTC agreement, and the influence of the IATTC increased. With the increased reliance on the IATTC agreement, the Mexican bilateral agreement was terminated in 1965. About 8 million square miles of the ETP is designated as the IATTC's Yellowfin Regulatory Area, wherein most of the yellowfin tuna purse seine fishery is conducted.
Yellowfin Tuna Purse Seine Fishery
For a variety of reasons, schools of large, mature yellowfin tuna regularly congregate and swim beneath schools of dolphins in the ETP. U.S. fishermen began to exploit this association in the late 1950s by encircling the dolphin schools with large purse seine nets to capture the yellowfin tuna swimming beneath the dolphins. Purse seine nets may be a mile in length and hang as deep as 600 to 800 feet beneath floats on the ocean surface. After a dolphin school is sighted, speedboats are launched for a high-speed chase to tire and herd the dolphins into a tight group amenable to net encirclement -- chase and herding lasts an average of 20 minutes, with some extreme chases lasting more than an hour. The purse seiner surrounds the dolphin school with the net, with a large skiff holding one end of the net stationary. Upon encirclement, the bottom of the net is drawn together (pursed) by cables to keep tuna from diving beneath the net to escape.
The United States provided an expanding market for tuna as U.S. per capita tuna consumption more than doubled between 1950 and 1965 until, by 1974, more than a quarter of all fish consumed in the United States was tuna. Approximately 30% of the world's yellowfin tuna harvest is taken from the ETP. The U.S. tuna seiner fleet was at its peak vessel number in 1979 when 140 purse seiners with a carrying capacity of 102,000 metric tons fished for ETP yellowfin tuna. Changes in the 1980s to more efficient, larger vessels reduced the U.S. ETP tuna seiner fleet to about 65 vessels with a combined capacity of about 100,000 metric tons by 1990.
However, despite efforts to release the entrapped dolphins (which were of no commercial value to the U.S. fishermen) while landing the tuna, dolphins became entangled in the nets and died by asphyxiation, since dolphins are air-breathing mammals. IATTC scientists claim that dolphin mortality is easily noticed and documented (i.e., little unseen mortality occurs) since dolphin carcasses float and are visible from a great distance. Others contest this statement, believing that not all dolphin carcasses float since, if a dolphin's lungs fill with water, the carcass should sink, only resurfacing after decomposition gasses accumulate.
Tuna seiners took early action to reduce dolphin mortalities. In 1957, acting on suggestions from experienced European purse seine fishermen, tuna seiners modified procedures to back-down vessels so as to release dolphins over the top of the purse seine net. In 1971, tuna seiner Harold Medina developed and introduced a special panel for seine nets that further reduced dolphin entanglement. These two methods were improved further after passage of the Marine Mammal Protection Act in 1972. Despite these efforts and prior to 1973, estimations based on limited data indicated that more than 300,000 dolphins may have died each year during U.S. purse seine fishing for yellowfin tuna in the ETP.
Dolphin populations in the ETP, particularly northeastern spotted and eastern spinner dolphins, declined due to mortalities from early tuna seining. The population sizes appear to have stabilized, but more years of monitoring will be required to determine whether these populations are recovering or not. About 88% of ETP dolphin encirclements by tuna seiners were conducted on spotted dolphins. Currently, eastern spinner dolphin stocks are estimated to be between one-half and one-fifth of their original abundance, while northeastern offshore spotted dolphin stocks are estimated to be about one-fifth of their original abundance. However, critics question the ability of managers to accurately back-calculate original dolphin abundance estimates, due to data limitations.
Under the authority of the Marine Mammal Protection Act (MMPA), eastern spinner dolphins were declared depleted on Aug. 26, 1993; northeastern offshore spotted dolphins were declared depleted on Nov. 1, 1993. Despite the estimated extensive mortalities, however, no ETP dolphin populations have been listed as endangered or threatened under the U.S. Endangered Species Act, although petitions for listing were submitted and denied. However, critics of current policy suggest that these two dolphin populations could warrant a threatened or endangered listing if recovery continues to prove elusive. Estimates of ETP dolphin populations of most concern, published in 1993, were northeastern spotted dolphins (588,700 to 970,400 animals) and eastern spinner dolphins (389,500 to 938,300 animals). Combined populations of all species of dolphins in the ETP fishery may total from 9.5 million to 10 million animals.
ETP Marine Ecology
The IATTC has conducted research on the food habits of dolphins, tunas, and other large open-ocean predators. Preliminary results indicate that yellowfin tuna are primarily daytime feeders, while spotted and spinner dolphins feed during the nighttime as well as at dawn and dusk. The two dolphin species differ in their prey -- spinner dolphins feed more often on small mid-water fishes such as lanternfish, while spotted dolphins feed on a wider variety of near-surface and mid-water fishes and squids. Mature yellowfin tuna feed primarily on near-surface fishes, squids, and swimming crabs. Both dolphin species and mature yellowfin tuna are generalist feeders and do not seek out specific prey species. Similar food habits may contribute to formation of the tuna-dolphin aggregations, but this appears not to be the major cause for such association.
Natural predators of dolphins and mature yellowfin tuna include large sharks and billfishes and some small whales such as false killer whales. Natural predation rates have not been estimated for either of the dolphin species or the yellowfin tuna.
Regulation of the ETP Yellowfin Tuna Seine Fishery by the MMPA
From its inception in 1972, one of the goals of the Marine Mammal Protection Act was to reduce the incidental mortality of dolphins in the ETP yellowfin tuna purse seine fishery to approach zero. The MMPA gave management authority for dolphins to the National Marine Fisheries Service (NMFS), within the National Oceanic and Atmospheric Administration in the Department of Commerce. Strict regulations promulgated by NMFS under MMPA authority set standards for tuna seining and motivated technological improvements in purse seine methods that substantially reduced dolphin mortalities in this fishery. By 1977, annual dolphin mortality attributable to U.S. tuna seiners had declined to about 25,450 animals (Table 1). Tuna industry sources, however, suggest that the dramatic 1972-1977 mortality decline for U.S. vessels was partially the result of better data collection methods validating a lower actual mortality, although critics consider this unlikely, given pre-1972 fishing techniques (notably no required back-down), which almost certainly resulted in higher mortality than was observed post-1972.
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The ETP purse seine fishery was dominated by U.S. vessels through the 1960s and into the early 1970s. By the 1980s, the U.S. fleet was consolidating as high interest rates and increasing fuel costs encouraged the replacement of older vessels by fewer, larger, more efficient tuna seiners. A strong El Nino event and a growing Asian cannery industry in the early 1980s induced more U.S. vessels to relocate to the Western Pacific. In addition, some U.S. tuna seiners were sold and reflagged in foreign nations, and many inexperienced foreign operators entered the fishery. With these shifts, annual dolphin mortality began to increase again until more than 100,000 dolphins were killed by foreign tuna purse seine vessels in 1986. As foreign-caused dolphin mortalities rose, various U.S. interests sought ways to encourage or pressure foreign tuna harvesters to place more emphasis on reducing dolphin mortalities.
Meanwhile, the IATTC coordinated efforts to disseminate information to foreign tuna fleets concerning how purse seine nets might be modified to pose less of an entanglement threat for dolphins, and how fishing methods could be modified to allow more dolphins to escape without obvious injury after encirclement. In 1977, the IATTC established a tuna-dolphin investigation whose objectives included reduction of dolphin mortality and ensuring the survival of the dolphin stocks involved in the fishery.
Congress responded in 1984 and 1988 by amending the MMPA to establish comparability standards for foreign tuna harvesters interested in exporting their catch to the U.S. market. However, with the number of U.S. vessels in the ETP declining, the comparability standards became progressively more difficult for foreign nations to meet. After the 1988 amendments, the threat of embargoes and potential loss of the U.S. tuna market encouraged the foreign tuna industry to develop more non-U.S. markets for their tuna. In addition, IATTC extension services, gear research, and the initiation of dolphin mortality limits in 1992 played a major role in reducing mortality by foreign seiners. A more pessimistic description of the resulting situation in the foreign tuna industry mentions trade havoc, collapsed global tuna prices, capital flight, soured international relationships, decimated fleets, and a near collapse of the ETP fishery's international management regime.
Current (1995) ETP dolphin mortality levels are well below the potential biological removal (PBR) levels for marine mammals mandated by the MMPA for U.S. fisheries other than ETP tuna seining. PBRs are designed to be conservative limits that would allow marine mammal populations to return to and be maintained at or above their optimum sustainable population level. The total PBRs for all ETP dolphin stocks in 1996 is greater than 50,000 dolphins, while current mortality is less than 4,000 animals. Both NMFS and IATTC scientists agree that current levels of dolphin mortality are low enough that the populations will recover, given that certain assumptions are satisfied, including that the chase and encirclement do not have a negative effect on the dolphins.
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