1

Introduction

Approximately one quarter of the world's tuna catch takes place in the eastern tropical Pacific Ocean (ETP). In that area (usually defined as east of 150° W, sometimes 160° W), the most economically important tuna species, the yellowfin (Thunnus albacares), often is found in association with various species of dolphins. * Since the late 1940s, tuna fishermen increasingly have taken advantage of this association and catch tuna by setting their nets around the highly visible herds of dolphins, which, being mammals, must surface often to breathe. Despite improvements in techniques and in gear that have substantially reduced the number of dolphins killed in the ETP tuna fishery, thousands of dolphins are still killed each year.

When the Congress reauthorized the Marine Mammal Protection Act of 1972 on November 23, 1988, it stipulated several amendments to the act. One of these amendments (Section 110 (a)) focused on identifying appropriate research into promising new methods of locating and catching yellowfin tuna without the incidental capture of dolphins. It further directed the Secretary of Commerce to “contract for an independent review of information pertaining to such potential alternative methods to be conducted by the National Academy of Sciences with individuals having scientific, technical, or other expertise that may be relevant

* Dolphins and porpoises are small, toothed, whale-like marine mammals (cetaceans). The term “dolphin” is usually applied to members of the family Delphinidae; “porpoise” usually refers to members of the family Phocoenidae. Some people refer to the whole group as porpoises; others, as dolphins. Some confusion results from the latter term because the fish Coryphaena hippurus is also commonly called dolphin (this is the American Fisheries Society's approved common name (Robins et al., 1991)). However, because the cetaceans most affected by the tuna fishery are members of the family Delphinidae, we refer to them as dolphins in this report.



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DOLPHINS AND THE TUNA INDUSTRY 1 Introduction Approximately one quarter of the world's tuna catch takes place in the eastern tropical Pacific Ocean (ETP). In that area (usually defined as east of 150° W, sometimes 160° W), the most economically important tuna species, the yellowfin (Thunnus albacares), often is found in association with various species of dolphins. * Since the late 1940s, tuna fishermen increasingly have taken advantage of this association and catch tuna by setting their nets around the highly visible herds of dolphins, which, being mammals, must surface often to breathe. Despite improvements in techniques and in gear that have substantially reduced the number of dolphins killed in the ETP tuna fishery, thousands of dolphins are still killed each year. When the Congress reauthorized the Marine Mammal Protection Act of 1972 on November 23, 1988, it stipulated several amendments to the act. One of these amendments (Section 110 (a)) focused on identifying appropriate research into promising new methods of locating and catching yellowfin tuna without the incidental capture of dolphins. It further directed the Secretary of Commerce to “contract for an independent review of information pertaining to such potential alternative methods to be conducted by the National Academy of Sciences with individuals having scientific, technical, or other expertise that may be relevant * Dolphins and porpoises are small, toothed, whale-like marine mammals (cetaceans). The term “dolphin” is usually applied to members of the family Delphinidae; “porpoise” usually refers to members of the family Phocoenidae. Some people refer to the whole group as porpoises; others, as dolphins. Some confusion results from the latter term because the fish Coryphaena hippurus is also commonly called dolphin (this is the American Fisheries Society's approved common name (Robins et al., 1991)). However, because the cetaceans most affected by the tuna fishery are members of the family Delphinidae, we refer to them as dolphins in this report.

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DOLPHINS AND THE TUNA INDUSTRY to the identification of promising alternative fishing techniques. ” The report from the National Academy of Sciences would then be submitted by the Secretary, together with a proposed plan of research, development, and implementation of alternative fishing techniques, to the Committee on Commerce, Science, and Transportation of the Senate and the Committee on Merchant Marine and Fisheries of the House of Representatives. This report provides background information on catching yellowfin tuna in the ETP and the incidental capture of dolphins, recommendations from workshops focusing on improving current fishing techniques, and recommendations from the Committee on Reducing Porpoise Mortality from Tuna Fishing for research on alternative techniques. THE PROBLEM Catching tuna with purse seines is the most productive method available. There are three major modes of fishing this way. The first is school fishing, in which schools of tuna near the surface are found visually and the purse seine is set around the school. The second, called log fishing, depends on the attractive power of floating objects for tuna. Purse seines are set around natural logs or fish-aggregating devices and catch the fish that are often associated with them. The third method—the focus of this report—is “dolphin fishing.” Yellowfin tuna and certain species of dolphins are often associated, especially in the ETP. (The extent and effects of dolphin-associated tuna fishing in other oceans are poorly quantified or unknown.) Dolphins frequently come to the surface to breathe and thus are easy to see from a boat. The purse seine is set around the dolphin herds, and because the tuna are closely associated with them, catching dolphins usually means catching tuna as well. Although a variety of techniques and equipment have been developed to release the dolphins safely, thousands are still killed each year by dolphin fishing. Although all three methods of purse seining catch tuna, log and school fishing catch mostly small, sexually immature tuna. Dolphin fishing usually catches large fish that are often sexually mature and produces larger average catches than the other methods. Thus, redirecting the fishing away from tuna associated with dolphins would be less efficient and would have a negative effect on the yield of the fishery and perhaps on the conservation of tuna populations. From the point of view only of economics and harvesting tuna, large tuna should be sought; fishermen should fish on dolphins and be discouraged from fishing on logs or schools. However, dolphin fishing kills dolphins; to minimize the killing of dolphins, all fishing should be directed away from dolphins. This dichotomy is the basis of the tuna-dolphin problem. Two operational factors are related to the total number of dolphins killed in purse seining for tuna. The first is the number of times purse seines are set around dolphins, and the second is the average number of dolphins killed in

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DOLPHINS AND THE TUNA INDUSTRY each such set. The first factor is affected by market prices and availability of tuna of different sizes, restrictions such as the policy of some processors not to buy tuna caught on trips that have involved the intentional encirclement or death of dolphins (so-called “dolphin-safe” tuna), and the availability of alternative methods of catching tuna. The second factor depends on conditions such as the fishermen 's motivation, skill, and experience; the condition of the vessel's equipment; weather conditions; and technological developments. Therefore, two general approaches are available to achieve the goal of reducing dolphin mortality—economic and technical—and each approach has several options. BACKGROUND ON REDUCING DOLPHIN MORTALITY FROM TUNA FISHING The Current Tuna Fishery and Its Development More than 70 nations participate in the world tuna fishery, but only 10 of them account for almost 85% of the catch. They are Japan, which accounts for about 29%; the United States, 12%; Spain, 8%; the Republic of Korea, 6%; the Philippines, France, Indonesia, and Mexico, 5% each; the Republic of China, 4%; and Venezuela, 3% (IATTC, 1989a). About 36% of this catch is consumed by Japan and about 31% by the United States (IATTC, 1989a). Over the years, one of the most productive tuna fishing areas has been the ETP. On an average, this area accounts for nearly one quarter of the world tuna catch (IATTC, 1989a). Albacore or longfin tuna (Thunnus alalunga) has been fished commercially off southern California since the turn of the century. It was the first tuna to be canned and is the only tuna known as “white-meat” tuna. As the demand for canned tuna increased, southern California fishermen ventured off the coast of Mexico to catch yellowfin and skipjack tuna (Katsuwonus pelamis) and by the 1920s, by which time bait could be kept alive for days, boats ventured farther offshore. In the 1930s, mechanical coolers made it possible to freeze the catch on board, further freeing the vessels to explore offshore waters; a fishing area developed as far south as the equator and up to several hundred miles offshore where yellowfin and skipjack tuna were the target species. Synthetic webbing and the advent of the Puretic power block in 1955 led to the completion of transforming bait boats to ocean-going purse seiners capable of staying at sea for a month or more. The fishery continued to expand southward to Peru and Chile, and during the late 1960s and the 1970s, it expanded farther offshore to about 145° W. The capacity to operate far offshore led vessels to areas where yellowfin tuna were more abundant and where they associated more frequently with dolphins than they did nearer the coast (Hofman, 1981). A major fishery for yellowfin caught in association with

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DOLPHINS AND THE TUNA INDUSTRY dolphins developed. In this fishery, purse seines are set around herds of dolphins and schools of tuna with the intention of retaining the tuna and releasing the dolphins. (Skipjack tend to be caught close to shore, and less than 0.4% of the total catch is caught in association with dolphins.) These changes and economic considerations made purse seining so efficient that by 1961 nearly all of the larger bait boats had been converted to purse seiners. Since then, purse seiners have been the dominant type of vessel in the fishery (98% of the mean 1984–1988 capacity) (see Table 2 in IATTC, 1989a). The annual catch of yellowfin tuna in the Pacific Ocean east of 150° W was approximately 159,000 metric tons in 1980 with a value of approximately $192 million. After a decline in the El Niño years of 1982–1983, the catch in the area increased to 269,000 metric tons in 1986 (IATTC, 1987). In Table 1-1, the Inter-American Tropical Tuna Commission (IATTC) data on the fishery for yellowfin in the ETP are broken down by fishing mode (dolphin vs. non-dolphin), area (inside and outside 200-mile national Exclusive Economic Zones), and fleet (U.S. vs. non-U.S.). Dolphin fishing includes all sets made on tuna associated with dolphins; non-dolphin includes all other purse-seine sets. Note that (1) 67% of the dolphin catch is taken outside the Exclusive Economic Zones, and 84% of the non-dolphin catch within them; (2) 77% of the U.S. catch of yellowfin in the ETP and 59% of the non-U.S. catch are dolphin catch; and (3) 84% of dolphin sets involve spotted dolphins, in either pure or mixed herds. In Figure 1-1 and Figure 1-2 it can be seen that the TABLE 1-1A Mean ETP Yellowfin Catch in Thousands of Metric Tons, by Fishing Mode, Area, and Fleet, 1984–1988a Area and Fleet Dolphin Non-dolphin Total Inside 200 miles 50.8 73.5 124.3 Outside 200 miles 101.4 12.0 113.3 Total 152.2 85.5 237.6 U.S. Fleet 66.1 19.4 85.5 Non-U.S. Fleet 89.2 62.4 151.6 Total 155.3 81.8 237.1 TABLE 1-1B Percentage of Sets on Different Types of Dolphin Herds, 1984–1988 a Type of Dolphin Herd Percentage Spotted Pure 45.5 Spotted + Eastern Spinner 21.9 Spotted + Whitebelly Spinner 16.5 Spinner Pure 1.7 Common Dolphin 4.6 Other 9.8 Total 100.0 a Data from IATTC.

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DOLPHINS AND THE TUNA INDUSTRY geographic distribution of the catch of yellowfin and skipjack tuna is different for dolphin and non-dolphin fishing. The figures refer to April–September 1986, but are representative: in general, tuna associated with dolphins are caught farther offshore than those caught in non-dolphin fishing. Until recently, the fishery was dominated by the U.S. fleet. A small tuna fishery existed in Mexico before World War II, and during the 1950s, tuna fisheries were developed in Peru and Ecuador. However, the fleets were small and the combined catch of these countries at that time amounted to less than 10% of the total catch from the eastern Pacific. Since 1960, fleets of nations other than the United States have increased greatly by construction of new vessels and transfer of flags, and the U.S. fleet has decreased. The proportion of the catch taken by U.S. vessels decreased from 90% in 1960 to 32% in 1988 and 11% in 1991, and that taken by Latin American countries bordering the Pacific Ocean increased from 10% to 47% in 1988 and 57% in 1991 (IATTC, 1989a; M. Hall, IATTC, La Jolla, Calif., personal commun., 1991). Until about 1975, the U.S. market consumed about 80% of the catch of surface-caught (i.e., by bait-poles and purse seines) tuna from the ETP. With FIGURE 1-1 Dolphin-associated sets. Eastern Pacific real distribution of yellowfin and skipjack tuna purse-seine catch for April–September 1986 from usable log-book data. (1 short ton = 0.907 metric ton.) Source: Richard Deriso, IATTC, La Jolla, CA, unpublished material.

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DOLPHINS AND THE TUNA INDUSTRY FIGURE 1-2 Non-dolphin-associated sets. Eastern Pacific areal distribution of yellowfin and skipjack tuna purse-seine catch for April–September 1986 from usable log-book data. (1 short ton = 0.907 metric ton.) Source: Richard Deriso, IATTC, La Jolla, CA, unpublished material. the expansion of the non-U.S. fleets during the 1980s, the share of the catch absorbed by the U.S. market declined, falling to 45% in 1987. Most of the difference went to Latin America, Europe, and the Far East (IATTC, 1989a). Of particular interest to the committee is the surface fishery for yellowfin tuna in the ETP. Surface-caught yellowfin and skipjack tuna provide the raw material for the canned light-meat tuna product marketed primarily in the United States, Europe, and the Far East. Over the years, as new fishing areas have become viable, the ETP has contributed a smaller fraction of the world catch of yellowfin and skipjack. Dolphin Mortality Associated with the Tuna Fishery Although no accurate data are available for the early years (1950 –1972), the increased offshore operation of increasingly sophisticated fishing vessels setting their nets on dolphin herds clearly led to very high mortality in the ETP. Estimates of dolphin mortality (e.g., Perrin, 1968, 1969; NMFS, 1980a; Lo and Smith, 1986) are based on extremely small, nonrepresentative, and probably biased data sets,

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DOLPHINS AND THE TUNA INDUSTRY vary from one investigator to another, and vary from year to year. Nonetheless, it seems likely that from 1960 to 1972, more than 100,000 dolphins were killed each year by the U.S. fleet. After 1972, the annual number killed by the U.S. fleet declined to approximately 20,000 in 1979—23,595 according to Hofman (1981) and 17,938 according to the National Marine Fisheries Service (NMFS, 1980a); IATTC (1991a) estimated total 1979 mortality at 21,467. In 1988–1990, the annual U.S. kill according to NMFS was 19,712 in 1988, 12,643 in 1989, and 5,083 in 1990 (MMC, 1991). This decline was due to a decrease in the rate at which tuna boats killed dolphins (Wahlen, 1986) and a decrease in the number of boats in the U.S. fleet. Most of the tuna fleet is now registered in other countries; by 1986, only 34 boats of the 103-boat fleet were registered in the United States and subject to NMFS regulations (NMFS, 1987). IATTC (1991a) estimated that the total kill for 1989 was 97,000–102,000 dolphins, of which the 12,643 attributed to the U.S. fleet was less than 15%. In 1990, the total mortality declined to 52,000–56,000 dolphins (IATTC, unpublished data), less than 10% of which (5,083) was caused by the U.S. fleet. To date in 1991 (M. Hall, personal commun., 1991), average mortality per set has fallen to half of the 1990 values; this, added to a reduction of fishing effort on dolphins, is projected to result in a total mortality of about 25,000 dolphins for the whole international fleet in 1991. Three species of dolphins are most commonly affected: the spotted dolphin (Stenella attenuata), the spinner dolphin (Stenella longirostris), and the common dolphin (Delphinus delphis). NMFS, which has responsibility for protecting marine mammals under the Marine Mammal Protection Act of 1972, set an annual quota in 1980 of 20,500 dolphins that could be killed by U.S. tuna boats, that quota including subquotas for various species and stocks. Additional regulations apply to fishing techniques. Reducing Dolphin Mortality Improvements in fishing gear and techniques discussed in Chapter 3 and Chapter 7, the mandatory observer program, and the kill quota were responsible for the dramatic decline in the number of dolphins killed by boats in the U.S. fleet. Currently, only about 0.5% of dolphins encircled by purse seines are injured or killed and almost all of those are killed in a small number of “problem” sets (NMFS, unpublished data). Most sets on dolphins are zero-kill sets. Three major advances have influenced the reduction in dolphin kills. The first is a procedure developed by tuna fisherman Anton Misetich known as “backdown,” in which the seine is pulled out from under the dolphins, thus allowing them to escape without losing the fish in the net. The second advance is the use of Medina panels. Designed by tuna fisherman Harold Medina, strips (panels) of relatively fine-mesh sections of net about 33 feet deep are placed adjacent to the backdown area and below the corkline. The fine mesh is small enough to prevent the entanglement of the

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DOLPHINS AND THE TUNA INDUSTRY the corkline. The fine mesh is small enough to prevent the entanglement of the snouts and flippers of dolphins in the net and thus has a major effect in reducing dolphin mortality. Third, several methods have been developed to aid the release of dolphins from the net, such as the use of speedboats equipped with towing bridles to keep the net open and the use of a raft inside the net to facilitate hand rescue. Many other modifications of gear and techniques have been tried, but the three mentioned above have played the largest role in reducing mortality. The NMFS regulations reflect this: They require all purse seiners to use Medina panels and to carry at least two speedboats and an inflatable raft. Backdown is required. Night sets on dolphins are also prohibited and bringing live marine mammals on board is prohibited. All those modifications were implemented more than a decade ago. More recent declines in mortality can be traced to improvements in equipment and the performance of the fishermen. Industrial groups have set up national technical advisory offices that in collaboration with IATTC include organizing training courses for vessel captains and crews, inspecting the condition and performance of dolphin-saving gear, and diagnosing individual vessel or skipper problems. The Porpoise Rescue Foundation, funded by the tuna industry, has also contributed ideas and methods to reduce dolphin mortality. The recent declines in mortality, from 130,000 dolphins in 1986 to perhaps as few as 25,000 in 1991, were achieved without any major technological advances or additions to the fishing gear. Although mortality of dolphins has been drastically reduced, the annual kill is still substantial. In addition to being of humanitarian and ecological concern, the killing of dolphins is detrimental to fishermen. For example, they have to disentangle the animals from the nets, a long and sometimes dangerous procedure. Furthermore, fishermen view the dolphins as a valuable resource because they attract and hold large yellowfin tuna near the surface where they can be caught. Thus, reducing dolphin mortality as much as possible is in their interest. Several workshops have focused on improving current fishing techniques and the development of alternative ones (Ralston, 1977; Hofman, 1979, 1981; NMFS, 1986; DeMaster, 1989). Participants in these workshops included representatives of the U.S. Navy, the National Science Foundation, the tuna and other industries, the Porpoise Rescue Foundation, academe, the Marine Mammal Commission, NMFS, IATTC, and various environmental organizations. The workshops have been distinguished by a spirit of cooperation. At a workshop held in October 1988 several points received consensus. No single alternative to purse-seine fishing on dolphins has proved acceptable thus far to the tuna industry. The industry will continue to work toward reducing dolphin mortality

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DOLPHINS AND THE TUNA INDUSTRY due to tuna fishing, but if purse-seine fishing on dolphins continues, some dolphin mortality will occur. Available information is insufficient to identify or evaluate alternative methods; additional research is necessary and desirable. Research should focus on alternative methods that appear most promising. These are using longlines; understanding and breaking the tuna-dolphin bond; locating and catching schools of yellowfin tuna not associated with dolphins; and using new technology such as fish-aggregating devices, longrange sonar, and remote sensing. THE COMMITTEE'S STUDY Because of concerns over the incidental capture and death of dolphins in operations of yellowfin tuna fishing, the U.S. Congress requested that the National Research Council (NRC) form a committee to search for promising new techniques for locating and catching yellowfin tuna without killing dolphins. The NRC Board on Biology, in collaboration with the Board on Environmental Studies and Toxicology and in consultation with the Marine Board, has convened this committee of experts on tuna and dolphin biology (including behavior and ecology), fishing-gear design and operation, fishery and wildlife management, resource economics, hydroacoustics and communication systems, and remote sensing. The committee has reviewed aspects of the scientific and technical information concerning the following topics, as they bear on the tuna fishery and the incidental killing of dolphins: Biology and ecology of yellowfin tuna. Biology, ecology, and behavior of dolphins at risk from purse seining. Economic and management implications of harvesting tuna of various sizes and ages. Development of economically viable alternatives to the setting of nets on dolphins. Nature of the tuna-dolphin bond and methods of breaking the bond while in and around nets. Evaluation of potential research leading to cost-effective methods of finding and catching tuna without killing dolphins. The committee did not evaluate various target levels of either dolphin population size or mortality. Some target levels are determined by ethics alone (e.g., zero mortality) and not science, whereas other target levels can be grounded scientifically (e.g., optimal sustainable population). The committee was not charged with selecting among various methods or targets for reducing dolphin mortality (for a discussion of this topic see Aron, 1988).