Tuna fisheries and resources
Peter Makoto Miyake
Federation of Japan Tuna Fisheries Cooperative Associations (Japan Tuna)
3 - 3 - 4, Shimorenjaku, Mitaka-shi
Tokyo 181-0013, Japan
The total world catch of tunas increased steadily from a half million tonnes in 1950 to a peak of almost 4 million tonnes in 1999. The catches in the Pacific Ocean have exceeded those of the Atlantic and Indian Oceans throughout this period, exceeding 2.5 million tonnes in 1998. The catches in the Atlantic Ocean increased more slowly that those in the other two oceans, and have stabilized since 1991. The catches in the Indian Ocean increased rapidly during the 1980s and 1990s, reaching a peak in 1999. The catches in the Indian Ocean have exceeded those of the Atlantic Ocean since 1987.
The greatest catches are those of skipjack tuna (2 million tonnes; 50 percent of the world catch), and the next-greatest catches are those of yellowfin (1 to 1.2 million tonnes; 25 percent of the world catch). The catches of these two species are taken mostly by surface gear, while greater portions of the catches of bigeye and southern bluefin are taken by longline gear. The catches of purse-seine vessels have increased steadily during the last five decades to 2.2 million tonnes, while those of longline and pole-and-line vessels have been stabilized in recent years at about 0.5 to 0.6 million tonnes.
During the 1950s and 1960s the catches of Japan and the United States exceeded those of any other country, but they have been stable since the 1970s, while those of other countries (the Taiwan Province of China, Spain, Indonesia, the Philippines, the Republic of Korea, France, Mexico and Venezuela) have increased greatly since the 1980s.
Technological developments in vessels, gear, navigation equipment and fishing procedures are described. The most important developments are freezers that freeze the fish very rapidly, making them acceptable for the sashimi market, longline fishing at greater depths, the invention of the hydraulic power block, increased carrying capacities of the vessels, use of fish-aggregating devices (FADs) for purse-seine fishing; and development of closed, refrigerated circulation of the bait tank for pole-and-line fishing. Other improvements, such as the use of satellite navigation systems, radar and sonar, are also discussed.
This paper provides general background information on important developments in the world tuna fisheries for a study of management of tuna fishing capacity. Quantifying the effects of these developments is not possible, so only qualitative descriptions are provided.
Fishing capacity cannot be evaluated without considering the catches of the various stocks of tunas, as well as the development of the fisheries, so summaries of catches appear in this report. More detailed information on the catches can be found in Miyake, Miyabe and Nakano (2004).
In this report the borders between the oceans follow the decisions by the Coordinating Working Party on Fishery Statistics (CWP). Each ocean includes all the adjacent seas (e.g. the Atlantic Ocean includes the Mediterranean Sea). Also, the data on the tuna catches include only the principal market species of tunas, albacore, bluefin, southern bluefin, bigeye, yellowfin and skipjack. Swordfish are discussed in a separate section.
The review of the fisheries is limited to the large-scale longline, purse-seine and pole-and-line fisheries, as these take the overwhelming majority of the catches of tunas. Nevertheless, the longline catch data used in this study include both large-scale and artisanal and/or coastal longliners, as the catches of these are combined in the catch data.
The CWP has recently decided that the Pacific and Atlantic bluefin tuna are different species (Thunnus orientalis and T. thynnus, respectively). It is impossible to distinguish these two by their appearance, however, and they are sold and bought without specification as to whether they are Atlantic or Pacific bluefin. Also, since they have been treated as a single species for many years, they are combined as "bluefin tuna" in this report.
There is only one stock of southern bluefin tuna, which occurs in all three oceans. Data on the catches of southern bluefin, by oceans, gear and countries, were not available at the time that this paper was written. Therefore, data on the catches of southern bluefin catch are not included in the analyses of catches of the principal market species of tunas by ocean and fishing gears, (e.g. Appendix 1, Tables 1 and 3), but they are included in those of the catches by species (e.g. Appendix 1, Table 2).
2.1 General developments
Developments in vessels, gear and fishing methods are discussed in this section. It is not possible to quantify the changes that have taken place over the last 50 years, but it is important to understand these developments when evaluating fishing capacity, since those directly affect fishing efficiencies.
There are three types, in general, of technological development; 1) to increase fishing efficiency; 2) to increase economic gain, though not increasing fishing efficiency; and 3) to make the fishing easier, safer and less labor-intensive. Even though 2) and 3) above do not directly increase fishing efficiency, they affect it indirectly.
Some of the developments are common throughout the fishing gears and/or type of fishing vessel, and some are specific to certain fisheries. Most of these developments increased fishing efficiencies, and hence increased the effect of fishing on the stocks, even if the capacities of the vessels did not increase.
2.1.1 Fishing vessels
There have been changes in construction materials. For the large industrial vessels, this occurred mostly during the 1940s. For the small coastal fishing vessels, light modern materials, such as fiberglass and plastic, have often been used since the 1960s.
Replacement of sails with engines began during the late 19th century, and by the 1940s most of the large vessels in the world had engines. The replacement of sails with engines has been expanding to the coastal artisanal fisheries as well.
The fishing vessels have continuously been increasing in size, which increases their fishing power and the safety of the crew.
Increases in engine power and efficiency of propellers (e.g. use of variable-pitch and large-diameter propellers) and reduction of resistance (such as bulbous bows) are always taking place. This increases fishing efficiency, and possibly saves labor.
When there are national or international regulations on fishing vessel size (e.g. carrying capacity or gross registered tons (GRT), vessels have been modified to conform with those restrictions.
Many types of equipment for determining vessel positions, such as Loran and Decca, have been developed.
During the 1960s non-military use of satellite systems became possible, and by the mid-1970s these became widely used by fishing vessels for positioning and for getting weather and fishing ground information.
The development, since the 1960s, of radio buoys has been beneficial to all fisheries. The improvements include "select call radio buoys" during the 1980s and "global positioning system (GPS) tracking radio buoys" during the late 1990s. These are useful for locating longlines drifting at sea and flotsam and artificial fish-aggregating devices (FADs) for purse seiners and pole-and-line vessels.
There have been continuous improvements in sonar and other equipment to measure oceanographic conditions.
2.2 The longline fishery
In 1914 the first powered longliners (30-70 GRT) began fishing in the western Pacific Ocean.
In 1953 the conversion from ice cooling systems to air blast freezers began, which enabled longliners to operate without restrictions as to their distance from the landing ports. The fish were frozen at about -25°C, which made them acceptable for canning, but not for the sashimi market.
More efficient freezers were developed during the 1960s, and by the end of that decade fish could be frozen at -55°C, which made them acceptable, for the first time, to the sashimi market.
By the mid-1960s the costs of labor and fuel in Japan had increased so much that longline fishing was no longer profitable. During the late 1960s the Japanese government and industry began a project to reduce the costs of labor, and the following changes were introduced: a line-casting device; a new method to attach and detach the branch lines; a line-hauling drum; a line winder; and, somewhat later, an automatic bait-attaching device. (However, the line-hauling drum and automatic bait-attaching device have not come into wide usage due to their bulk and technical complexity.) These innovations were soon adopted by longliners of other countries.
In 1967 double-deck longliners, which are more efficient for operations in the rough seas of higher latitudes, came into usage by vessels targeting bluefin and southern bluefin tuna.
During 1972-1973, slow-speed, large-diameter propellers, which made vessel handling easier and reduced costs, came into usage.
Beginning during the late 1960s, the vessels began to modify their gear by using fewer buoys, which had the effect of making most of the hooks fish at greater depths. This resulted in greater catches of bigeye, which brings higher prices than the other species of tunas (other than bluefin and southern bluefin, which are relatively rare).
2.3 The purse-seine fishery
The following events during the 1950s contributed to the development of the modern purse-seine fishery for tunas: invention of the hydraulic power block, which facilitated handling of the net; availability of synthetic netting, which did not deteriorate even in the tropics; and better facilities for freezing the fish (Orange and Broadhead, 1959; McNeely, 1961).
After the introduction of the power block, the sizes of blocks and the power of the winches have increased to further facilitate the fishing operations.
The use of auxiliary boats has increased. These may include: speed boats for herding dolphin-associated tuna schools prior to setting the net around them; use of pole-and-line vessels to attract fish schools, after which they can be surrounded by a purse seine; scouting and transport vessels for two-boat purse seining; and, auxiliary vessels for FAD fishing, mostly to keep good fishing grounds occupied and to assist in fishing operations.
Improvements in fish loading (removing fish from the seine, transferring them from the upper deck to the wells, etc.) have been made.
There have been changes in the structure of the nets in accordance with oceanographic conditions and behavior of the fish. Deeper nets are used in the western Pacific Ocean, where the thermocline is relatively deep, than in the eastern Pacific Ocean, where it is relatively shallow. Also, the nets now sink more rapidly. Accordingly to Delgado Molina et al. (1999) the average set in the Atlantic Ocean took 2.43 hours during the 1970s, but only 1.8 hours during the 1990s.
The use of bird radar, which is very effective in finding flocks of birds (which are frequently associated with schools of tuna), was introduced in 1987 (Delgado Molina et al., 1999). By 1991 the range of bird radar had been extended considerably.
Fishing on the schools associated with flotsam has been practiced by surface fisheries in all oceans, but particularly in the western and central Pacific Ocean. The use of FADs began during the late 1980s and early 1990s. FAD fishing is much different from other surface fisheries, as searching for fish schools is no longer necessary. This also changed the species and size compositions of the catches, most notably increasing the portion of small bigeye in the catches.
2.4 The pole-and-line fishery
Equipment for aeration of the bait wells and for freezing the catch was introduced in 1953, which resulted in significant expansion of the fishing grounds.
Use of forced circulation of seawater in the bait tanks began in 1963.
The first large pole-and-line vessel with forced circulation and brine freezer was built in 1965. Until the mid-1960s many Japanese pole-and-line vessels (whose catches exceeded those of pole-and-line vessels of all other countries) were engaged in longline fishing for tunas during the off-season. These developments made it possible for a vessel to engage in pole-and-line fishing throughout the year.
An automatic (robot) pole-and-line fishing device and fiberglass poles were introduced in 1965. The automatic fishing device made it possible to reduce the number of crew members, but it never came into wide usage because the catch rates were not as high as those of boats without this device.
After several years of experimentation, a complete closed cooling and circulation system was established for the bait wells in 1980. This released the vessels somewhat from restrictions on fishing grounds imposed by lack of baitfish.
Historical trends in the catches of tunas throughout the world are summarized in this section. Further details can be found in Miyake, Miyabe and Nakano (2004).
3.1 Data sources
3.1.1 Catch data
The data bases prepared by the following regional fishery management organizations (RFMOs) were used in this study.
International Commission for the Conservation of Atlantic tunas (ICCAT) for the Atlantic Ocean,
Indian Ocean Tuna Commission (IOTC) for the Indian Ocean,
Inter-American Tropical Tuna Commission (IATTC) for the eastern Pacific Ocean (east of 150°W),
Secretariat for the Pacific Community (SPC) for the western and central Pacific Ocean, excluding Pacific bluefin and North Pacific albacore,
Interim Scientific Committee (ISC) for Pacific bluefin and North Pacific albacore and
Commission for the Conservation of Southern Bluefin Tuna (CCSBT) for southern bluefin tuna in all oceans.
These data bases include data through 200l or 2002. The data are frequently updated, and sometimes major revisions to historical data series are introduced. Data downloaded on 30 September 2003 were used in this study. As they are more recent, the data used in this report differ from these used in the previous studies (Miyake, Miyabe and Nakano, 2004). The important changes for the historical data series are as follows:
Japanese longline catch data in the Indian and Pacific Oceans for the 1950s and 1960s have been considerably changed, due to the revision in conversion procedures for numbers of fish to round weights of fish.
New data for the Taiwan Province of China became available for the 1950s for the Indian Ocean.
Data for the catches of the Taiwan Province of China in the Pacific Ocean since 1992 were revised, based on new compilations of logbook data.
The purse-seine catches reported as mixed tunas in the Pacific Ocean have been disaggregated into bigeye, yellowfin and skipjack, using species-sampling data.
Almost all the above data bases (with exception of those for the Atlantic Ocean) include data for 1952 through 2001. The data for 1950 and 1951 are the author's estimates, and most of the data for 2000 and 2001 are preliminary.
3.1.2 Geographical distributions of the catches
The distributional maps were provided by the FAO Fisheries Department (published on a compact disk as Tuna Atlas and available on the FAO web site). The data base does not include data for the 1950s. These data are summarized in Appendix 2, Figs 1-4. Appendix 2, Figures 1-3 show the catches of all species combined by longline, purse-seine and pole-and-line gear during four periods, 1964-1966, 1974-1976, 1984-1986 and 1996-1998. Appendix 2, Figure 4 shows the distributions of the catches of 1998, by species and gear. Additional details are available in the Tuna Atlas.
The Appendix figures include data only for the fisheries for which the catches are reported by 5-degree areas. Therefore many components of the catch distributions are missing, although the coverage rate has increased in recent years. The data for the Atlantic Ocean are raised to the total annual catches, while those for the other oceans are not raised. Therefore the densities of the catches are not strictly comparable among oceans.
3.2 Global overview of tuna catches
The combined reported total world catches of the principal market species of tunas (not including southern bluefin tuna) in the three oceans are shown in Figures 1 and 2 and in Appendix 1, Table 1. The total world catches increased steadily from a half million tonnes in 1950 to almost 4 million tonnes in 1999.
The catches of the Pacific Ocean dominated throughout the period, exceeding 2.5 million tonnes in 1998 and every year thereafter. The rate of increase in the catch of the Atlantic Ocean has been much less than those of the other two oceans, the catches having been nearly stable since 1991 and having reached their highest level in 1994. The catches in the Indian Ocean were low until 1981, but thereafter increased until 1999, and have exceeded the catches of the Atlantic Ocean since 1987.
Currently the proportions of the catches among the oceans are about 15, 20 and 65 percent for the Atlantic, Indian and Pacific Oceans, respectively. It should be noted that bluefin, bigeye and albacore have been subject to more severe catch restrictions in the Atlantic Ocean than in the other two oceans.
The distributions of the average annual catches of the principal market species of tunas combined, by 5-degree areas and by fishing gears (longline, purse-seine and pole-and-line) are shown in Appendix 2, Figures 1-3.
The combined total world catches of the principal market species of tunas (not including southern bluefin tuna), by major fishing gears, are shown in Figure 3 and Appendix 1, Table 3. Additional information is given in Section 4 of this report and in Miyake, Miyabe and Nakano (2004).
The total world catches of the principal market species of tunas (including southern bluefin tuna), by species, are shown in Figure 4 and Appendix 1, Table 2 (all oceans combined) and in Figure 5 (not including southern bluefin tuna). It should be noted that the scales on y-axis (catch) differ among oceans in Figure 5.
The relative importance of the various species and the trends in catches by species are very different among oceans. The Atlantic catches are more evenly distributed among species, the bigeye catches being almost as great as those of yellowfin and skipjack. Although swordfish are not included in this report, it is worthy of note that it is relatively more important in the
Atlantic Ocean than in the other oceans. Albacore and bluefin were formerly the most important species. The albacore catches have been more-or-less stable since the early 1960s. The bluefin catches increased until 1996 and thereafter slightly decreased, most likely due to the catch quotas introduced by ICCAT.
In the Indian Ocean the catches of skipjack and yellowfin have been increasing since 1982, as a result of rapid development of the purse-seine fishery in the western Indian Ocean (Section 4.4). Since then the catches of those two species have been much greater than those of the other species. During the 1990s, however, the catches of yellowfin have been stable, or have even declined slightly, while those of bigeye have increased rapidly.
In the Pacific Ocean the catches of skipjack and yellowfin began to increase during early 1970s, much earlier than in the Indian Ocean. The catches of skipjack have exceeded those of yellowfin since the mid-1970s, and the dominance has become more pronounced in recent years. The relative importance of the catches of bigeye and albacore are less than in the other two oceans.
The world catches of the principal market species of tunas, by species and gear, are shown in Figure 6. The longline contribution to the albacore catch increased during the 1950s and early 1960s, and in recent years it has accounted for more than half of the total catch. Albacore is also harvested by pole-and-line gear, mostly in the Pacific Ocean, with peak catches during the mid-1970s.
The greatest share of the catch of bluefin has been made, by purse seiners, mainly in the northeastern Atlantic Ocean during earlier years and in the Mediterranean Sea and near Japan during recent years. The longline catch has been less important, with two peaks, one during the 1960s (mostly of fish caught off Brazil) and one in the mid-1990s. Other gears include traps, gillnets and handlines. The catch by traps was very important in the Atlantic Ocean during earlier years.
Bigeye catches were taken almost exclusively by longline gear prior to the mid-1970s. The longline catches increased until early 1990s, and then stabilized. While longline catch has been stable in recent years, the purse-seine catch has been increasing since the early 1990s, so the total catch continued to increase during the 1990s. The increased catch of bigeye by purse seiners is due mainly to increased use of FADs.
In general, the catches of skipjack and, to a lesser extent, yellowfin have dominated the world catches of tunas. Purse seines have increased their share of the catch to more than 60 percent of each of the two species. The catches of both species increased rapidly during the period (Figure 6). The increase in the catch of yellowfin slowed during the 1990s to a level of about 1 to 1.2 million tonnes (over 25 percent of the total), while the skipjack catch is still increasing, reaching its highest level of 2 million tonnes in 1999 (50 percent of the total). It should be noted that in 1999, when the world market price of skipjack declined due to oversupply, the purse-seine industry created the World Tuna Purse-seine Organization (WTPO) to limit the catch of skipjack.
The catch of southern bluefin increased rapidly until 1961 but after that it declined until 1990, after which it stabilized. The downward trend during the 1970s was due to voluntary catch restrictions by Japan, Australia and New Zealand, and, after that, during the 1980s, to regulations adopted by the CCSBT. During the earlier years the catches were made almost exclusively by longlines, but more recently the catches by surface gear, including gillnets, pole-and-line gear, and purse seines, have increased.
This section gives a brief overview of the development of the most important fisheries during the last 50 years. Some developments were the result of the technological improvements discussed in Section 2; some were more related to national and international policies for management of fish stocks and/or fishing fleets or to socio-economic elements. All these elements interact with one another and are often specific to countries, fisheries or fishing gears. The proportions of the world catches of the principal market species of tunas (not including southern bluefin tuna) taken by various fishing gears are shown in Figure 7. The proportions of the catches taken by purse-seine and other gears have increased, and that taken by pole-and-line gear has decreased. The proportion of the catches taken by longline gear increased to the mid-1960s, and decreased after that.
4.1 Overview by decades
Pre-1950s: Tuna fishing has been carried out in various parts of the world for many years. Those fisheries take place near coasts and islands. In the Atlantic Ocean these include purse seining for bluefin off Norway, trolling for albacore in the Bay of Biscay, trap fishing at the Strait of Gibraltar and along the coast of North Africa, bigeye and skipjack fishing near islands and artisanal fishing along the coast of West Africa. In the Pacific Ocean these include various artisanal fisheries near islands in tropical waters, albacore trolling off the west coast of the United States, pole-and-line and purse-seine fishing for yellowfin and skipjack by vessels based in California, pole-and-line, gillnet and purse-seine fishing by vessels based in South America, fishing for various species of tunas with various types of gear near Japan and fishing for skipjack and yellowfin in tropical waters of the western and central Pacific. In the Indian Ocean these include fishing for skipjack off Sri Lanka, India and the Maldives. Longline fishing for southern bluefin tuna took place off Australia.
1950s: Most of the fisheries that took place before 1950 continued during the 1950s. As a result of the increasing demand for tuna as a substitute for salmon in the canning industry, industrialized tuna fisheries began during the 1940s and 1950s. The Japanese longline fishery expanded, reaching the western Atlantic Ocean in 1957. Pole-and-line fishing continued in the eastern and in the western and central Pacific Ocean, and, during the late 1950s, European pole-and-line vessels fished in coastal waters off West Africa. A purse-seine fishery for bluefin tuna existed in the northeastern Atlantic Ocean, and toward the end of this decade purse-seine fishing for tropical tunas increased in the eastern Pacific Ocean.
1960s: European purse seiners began fishing for tropical tunas off West Africa in 1964. In the tropical eastern Pacific Ocean, off Central and South America, pole-and-line fishing was almost completely replaced by purse seining. A large portion of the yellowfin caught in this region is taken in association with dolphins. In accordance with a recommendation by the IATTC, a quota on the catch of yellowfin was adopted in 1965 (which would first take effect in 1966).
In the western and central Pacific Ocean the number of pole-and-line vessels increased, and the area of operation expanded (Suisanshinchosha, 1970). The catch reached a level of 250 000 tonnes. Due to the lack of data, the pole-and-line catches in the western and central Pacific Ocean are not shown in Appendix 2, Figure 3. Longline fishing further expanded into the Atlantic and Indian Oceans, covering most of the world oceans between 40°N and 35°S. The target species were still yellowfin and albacore (Figure 8). Again due to the lack of data, the longline catches in the Indian Ocean are not shown in Appendix 2, Figure 1.
1970s: The fishery in the tropical eastern Atlantic Ocean by purse seiners of European nations developed rapidly, with the primary catches being yellowfin and skipjack. Although strict regulations for the reduction of mortality of dolphins associated with tuna were implemented in the eastern Pacific Ocean, the fishery continued to develop there. However, some effort was diverted from the eastern Pacific to the western and central Pacific, where tunas do not associate with dolphins.
Pole-and-line fishing in the tropical eastern Atlantic and the western and central Pacific expanded in both fleet size and areas in which fishing took place. In contrast, the pole-and-line fishery in the eastern Pacific declined after the middle of the decade.
With the development of facilities for extremely cold storage and deep longline gear (Section 2), the longline fishery gradually changed its target species from albacore and yellowfin to bigeye (Figure 8). The changes affected the fishing areas and seasons, in addition to the species compositions of the catches.
1980s: More regulatory measures were introduced by the IATTC and ICCAT, which affected the fishing patterns, species compositions of the catches and the shares of the catches taken by vessels of various countries.
The purse-seine fishery that begun experimentally in 1974 in the western Indian Ocean expanded rapidly, as vessels that fished in the eastern Atlantic Ocean transferred their operations to the Indian Ocean. The fishing effort in the western and central Pacific and the eastern Pacific increased, and the effort expanded further offshore.
Pole-and-line fishing in the western and central Pacific and eastern Atlantic continued, and new pole-and-line fisheries began in the Atlantic off Brazil and off southern Africa
Deep-longline fishing, targeting bigeye, which was first carried out by Japanese vessels, was adopted by vessels of other nations. There were large changes in the distributions of ownership of longline vessels among the various nations. Small-scale longline fishing operations began in various areas by vessels registered in, among others, several Mediterranean countries, the Philippines and Indonesia.
1990 to present: More and more management measures have been introduced, and these have been circumvented by registration of vessels in countries that do not require their vessels to abide by the restrictions adopted by the international organizations responsible for the management of the fisheries. This illegal, unreported and unregulated (IUU) fishing jeopardizes the management of the fisheries, and has contributed to the increase of total tuna fishing capacity over most of the world.
The most important change for surface fishing is the introduction of FADs. The use of FADs has increased the catches of skipjack and small yellowfin, and especially bigeye, which were seldom taken by surface gear prior to the 1990s. Additional information on FADs is included in Section 4.4.
Pole-and-line fishing continued in the eastern and western Atlantic and in the western and central Pacific. The actual situation is not well represented in Appendix 2, Figure 3, as an important part of the data is missing.
Coastal states had begun chartering vessels registered in other countries during the 1980s, and this trend accelerated during the 1990s. Some of these chartered vessels changed flags to those of the coastal states, and this practice may be intensified in the near future. Partially due to the development of these new coastal fisheries, the fishing effort by traditional longline-fishing countries began to decline.
Tuna farming (keeping tuna in enclosed areas for several months to increase their fatness and have them ready for sale when the prices are higher) began during the 1990s, and nearly 20 000 tonnes of these were sold in 2000. The relatively small tunas taken by purse seiners that were formerly sold for canning can now be converted to products for the sashimi market. Until now, tuna farming has been pursued almost entirely with bluefin tuna, but the practice is spreading to bigeye and yellowfin tuna.
Small-scale longline fishing increased extensively, while the numbers of longline vessels that fish legally have decreased due to industry initiatives to limit fishing capacity.
The catches of artisanal fisheries (e.g. trolling, gillnets, handlines and miscellaneous unclassified gears) increased in the coastal and island countries.
4.2 The large-scale longline fisheries
The world catches of tunas by large-scale longline vessels are shown in Figure 8. As the catches by coastal small scale longliners have increased significantly during recent years, the catches by large-scale longliners are actually declining. The distributions of the catches of all species combined during representative years of the last four decades are shown in Appendix 2, Figure 1, and the distributions of the catches of four species during 1998 are shown in Appendix 2, Figure 4.
The longline catches of the principal market species of tuna increased rapidly during the 1950s, and during the 1960s more than 40 percent of the world catch was made by longline gear (Figure 7). The rate of increase was less from 1960 to 1990, and then somewhat greater from 1990 to 1993. After 1993 the longline catches have been declining. Due to the increased catches by purse-seine gear, longline gear now takes less than 20 percent of the total catch (Figure 7). During the earlier years the catch was taken almost exclusively by offshore longliners of Asian countries, which targeted yellowfin and albacore. During more recent years, with the entry of more coastal longliners into the fishery, the offshore longliners have directed their efforts more toward bigeye, bluefin, and southern bluefin, whereas the coastal longliners are mostly targeting yellowfin and bigeye.
4.2.2 Initial developments
Japanese vessels have always dominated the longline fishery for tunas, and all the technological developments discussed in Section 2 originated in Japan before being adopted by vessels of other nations. The only exceptions are some of the North American and European longline fisheries, which direct their effort mostly at swordfish.
The Japanese tuna fleet existed at the end of the 19th century, and 48 615 tonnes of tunas were caught in 1894 (Matsuda and Ouchi, 1984). The fishery expanded rapidly to the offshore waters of the western Pacific Ocean, with the boats using longline and pole-and-line gear alternatively, depending on the season. When Japan obtained the ex-Trustee Territories (0°-22°N, 130°-170°E) after World War I, facilities for producing dried skipjack sticks (katsuobushi) were constructed in Saipan and the Marshall Islands, and engine-powered vessels began fishing in those waters. This was probably the first industrialized tuna fishery in the world. The Japanese catch of tunas reached 202 439 tonnes in 1940, just before World War II.
4.2.3 The world-wide longline fishery
After World War II, which ended in 1945, the Japanese fishery was restricted to the nearshore areas. This restriction was lifted in 1952, and the fishery expanded rapidly. The expansion was assisted by the development of air-blast freezing to replace ice wells (Gyosen Kyokai, 1986). The fishing grounds expanded to the western and central Pacific Ocean, the eastern Pacific Ocean, the western Indian Ocean and the western tropical Atlantic Ocean during the 1950s. In 1958 the total longline catch reached 200 000 tonnes. During the initial post-war stage, the catches were frozen and maintained at about -20°C. The color of the flesh changed to brownish when the fish were thawed. These fish were not acceptable for consumption as sashimi, so the catch was mostly exported for canning. The vessels looked for the fishing grounds with high catch rates, regardless the species. The catches in tropical waters were mostly yellowfin, with some bigeye, and those in temperate waters were mostly albacore (which drew higher prices than yellowfin). At this stage, motherships of more than 3 000 GRT were widely used. There were two types of mothership, ones that accompany several independent longliners and ones that carry several small longliners on the deck. Foreign fishing bases were established in 1952. These had facilities for providing supplies to the vessels, receiving the catches for transshipment, and exchanging crew members. This contributed to the expansion of the fishing areas.
By the mid-1960s Japanese longliners were operating all over the world (Appendix 2, Figure 1). The Taiwan Province of China and the Republic of Korea began longline fishing during the early 1960s, mostly with used Japanese longliners with Japanese captains. At the same time vessels owned by residents of Japan, but registered in other countries ("flags of convenience"; FOC), entered the longline fishery. The Japanese government's policy of limiting entries to the tuna fishery was partially responsible for the growth of the Taiwan Province of China, Korean and FOC fleets.
Vessels of the Taiwan Province of China, Republic of Korea and FOCs had no domestic market for their catches, so they were sold in foreign markets for canning and later to the Japanese market for sashimi. Their fishing patterns were quite similar to those of the Japanese vessels, although the Taiwan Province of China and Korean vessels directed more effort toward albacore and yellowfin, respectively. This tradition has been maintained even to the current time. Since most of the Japanese foreign bases were operated by fishing or trade companies, the business of Taiwan Province of China, Korean and FOC vessels were accepted. Some bases were even maintained by a Japanese firm solely for non-Japanese vessels.
4.2.4 The sashimi fleet
A new era for the longline fishery began with the development of the extreme cold freezing and storage facilities (-40°C) in 1965. The use of such facilities had become common by 1969, with the fish frozen at -55°C (Gyosen Kyokai, 1986). The fish are frozen, and kept at temperatures that are low enough to prevent them from losing their fresh colour and flavour, and hence can be sold to the sashimi market. Consequently the longliners shifted their effort from fish used by the canning industry (yellowfin and albacore) to fish bringing the highest prices from the sashimi market, (bluefin and bigeye). The changes affected the fishing areas and seasons, in addition to the species compositions of the catches.
Adoption of extreme cold storage facilities changed the entire operating system, as most of the foreign-based cold storage facilities, except for those built in recent years, could not keep the fish at such low temperatures. The catches had to be taken back to Japan, either by the fishing vessels or by special freezer ships to which the fish were transferred in foreign ports or at sea. Also, mothership operations were terminated by 1975, due to their economic inefficiency.
At about the same time (the latter half of the 1960s), the Japanese industry developed several labor-saving devices, including: a line-casting device; a new method to attach and detach the branch lines; a line-hauling drum; a line winder; and, somewhat later, an automatic bait-attaching device. (The line-hauling drum and automatic bait-attaching device have not come into wide usage due to their bulk and technical complexity, but the others have been useful to the industry.)
Following the development of the extreme cold freezing facilities and the change in target species, the next important change, adoption of deep longlining gear, began during the late 1960s. The only change to the gear was decreasing the numbers of floats and attaching more branch lines between floats. Conventional line gear has four to six branch lines between floats, and fishes at 30 to 100 metres, while deep longline gear has up to 18 branch lines between floats and fishes at depths of more than 200 metres. Deep longlining gear, which has proven to be more efficient at catching bigeye, is now being used by almost all the Japanese longliners.
In 1967 double-deck longliners, which are more efficient for operations in the rough seas of higher latitudes, came into usage by vessels targeting bluefin and southern bluefin tuna.
Taiwan Province of China, Korean and FOC vessels adopted extreme cold freezing facilities and deep longlining about six to eight years after the Japanese vessels had done so. However, lesser portions of the Taiwan Province of China, Korean and FOC vessels have adopted these systems because the non-Japanese vessels tend to be older, and installation of new freezing facilities would not be economically feasible.
4.2.5 Initiatives in reducing fleet size and IUU fleet
During the 1980s the size of the Japanese longline began to decline, due to competition in the domestic market with the catches of Taiwan Province of China, Korean and FOC vessels, soaring labor and fuel costs, declining catch rates and a shortage of labor due to competition with other domestic industries. The growth of the Korean fleet began to slow down, but not that of the Taiwan Province of China fleet. Vessels of China entered the longline fishery during the 1990s. Their patterns of development have been almost identical with those shown by Taiwan Province of China and Korean vessels during the 1980s.
The FOC fleet changed its nature completely after the mid-1980s. During the 1980s, and increasingly during the 1990s, regulatory measures were adopted by the CCSBT, the IATTC, ICCAT, and the IOTC, henceforth referred to as Regional Fishery Management Organizations (RFMOs). As the measures were mandatory only to the contracting parties, some boat owners changed the registrations of their vessels to other nations that were not members of the RFMOs, and thus not subject of the regulations. The catches of old-type FOC vessels were generally reported by the countries in which their owners resided. However, data for the new-type FOC vessels are not available. Collectively, these vessels are known as Illegal, Unreported and Unregulated (IUU) fleet. Solutions for this problem were sought by the RFMOs, FAO and at the national level, and some effective measures, including trade restrictions, have been taken, so the size of IUU fleet is becoming reduced. At that time, the Taiwan Province of China and the Republic of Korea adopted limited-entry licensing system, but China continued to increase its fleet size. Finally, in 2001, China adopted a limited-license system.
FAO adopted its International Plan of Action (IPOA) for the Management of Fishing Capacity in 1999. In accordance with the spirit of the IPOA, Japan reduced its total fleet size by 20 percent in 2001. In 2002 the Organization for the Promotion of Responsible Tuna Fisheries (OPRT), an international organization of tuna industries of the major longline countries, was founded to reduce the amount of IUU fishing by changing the registrations of the FOC vessels to the countries in which their owners reside and then to scrap the excess vessels or convert them to some other use.
4.2.6 Other longline fleets, including swordfish longliners
The major large-scale longline fleets are discussed above. However, there are many longline fisheries in various parts of the world that are descendants of the Japanese longline fishery. These were introduced by the Japanese immigrants (Hawaii, Brazil, Mexico), created by transference of technology through establishing a fishing base (Venezuela, Brazil), or the result of charter arrangements through joint-ventures (Brazil, Uruguay, Canada, Iceland, Panama and Honduras). The vessels of those fleets are using gear and operating systems similar to those used by Japanese vessels, but sometimes at earlier stages in their development.
The only tuna longline fisheries that are not the direct descendants of the Japanese fishery are North American and European (Spain and Portugal) swordfish fisheries. These fisheries began during the 1970s, when restrictions on the mercury content of the fish were lifted in the United States. The swordfish longline fishery uses steel leaders and fluorescent light sticks to attract the fish. The gear is set at night, and the hooks are much closer to the surface than are hooks set for tunas. Monofilament main lines have been used since the late 1990s. The lines are installed into a drum. Normal tuna longline vessels (particularly those of the Taiwan Province of China) occasionally direct their effort at swordfish, depending on the area and season of operation. Those vessels use the same gear as for tuna, but add floats so that the hooks will fish closer to the surface, and set the gear at night.
4.3 The small-scale longline fishery
The small-scale longline fishery has also had a long history. Much of the technology was inherited from that used by Japanese large-scale longliners. During 1928-1929, Japan established a tuna base at Kaosiung, Taiwan Province of China, which was under its jurisdiction at that time. In 1937 200 vessels of about 14-15 gross tons based in Kaosiung were fishing at distances of up to 1000 miles from this base. Japan also established fishing bases in what are currently Indonesia and the Philippines. In 1940 139 033 tonnes of tunas were caught by these vessels (Matsuda and Ouchi, 1984).
After World War II these vessels resumed fishing in these areas and became coastal small-scale tuna fleets. The small-scale fleet in the Taiwan Province of China was the basis for the development of the large-scale longline fleet of the Taiwan Province of China during the 1960s, but at the same time the small-scale longliners based in the Taiwan Province of China continued to fish, and the numbers of such vessels increased. Their fishing grounds are mostly in the western Indian Ocean, the East China Sea and the tropical western Pacific Ocean. Except for bluefin tuna in the East China Sea in the summer, the target species are yellowfin and bigeye tunas. During the late 1980s these small-scale longliners expanded their fishing grounds toward the west and south and began landing their catches at foreign ports, mostly in Indonesia and Thailand. During the 1990s the catches increased rapidly, in respond to an increase in demand and better transshipment of the catches by air. These catches might have amounted to well over 100 000 tonnes by the early 2000s. The most of these vessels preserve their catches with ice. The fish of best quality are shipped by air to Japan for the sashimi market, while most of the rest are shipped to the United States for the fresh fish market. There is also some local consumption in the Taiwan Province of China and the Republic of Korea.
The author has tried to separate the catches by small-scale longliners from the total longline catch. This is difficult, however, as most of the catches of small longliners are not reported separately, or are reported as the catches of "unclassified" gears.
Small-scale longline fishing for tunas began on the east and west coasts of the United States during the 1980s. The techniques were not derived from those of Japanese longliners, but are more similar to salmon longline gear, which uses a drum reel for the main line. Small-scale longline fisheries, using similar systems, is beginning in many other parts of the world, e.g. Australia and Reunion.
4.4 The purse-seine fishery
The proportions of the world catches of the principal market species of tuna, by fishing gear, are shown in Figure 7, and the world purse-seine catches of the principal market species of tuna by species, are shown in Figure 9. It is apparent from these two figures that during the 1950s only about 10 percent of the catch was taken by purse seiners and that most of that catch was bluefin tuna. However, the purse-seine catches increased greatly during the second half of the 20th century, from almost nothing during the early 1950s to about 2.2 million tonnes in 2000 (Figure 9). By the mid-1970s the purse-seine catch exceeded that of any other gear, and by the mid 1980s the purse-seine catch exceeded those of all other gears combined (Figure 7). The major species caught since 1960 have been skipjack and yellowfin. The catches of bigeye began to increase during the early 1990s, but the catches of this species are still far less than those of skipjack and yellowfin. The leveling off of the catches of skipjack during the late 1990s and early 2000s is at least partly the result of catch controls adopted by the purse-seine fishing industry.
The distributions of the catches of all species combined by purse seiners during representative years of the 1960s, 1970s, 1980s and 1990s are shown in Appendix 2, Figure 2, and those for the individual species for 1998 are shown in Appendix 2, Figure 4. Bluefin were first caught by purse seiners off California in 1915 (Scofield, 1951), and yellowfin and skipjack were being caught by purse seiners in the eastern Pacific Ocean "since immediately after World War I" (Shimada and Schaefer, 1956). During the early years most of these vessels also fished for sardines and mackerel, but later some of them fished exclusively for tropical tunas. Bluefin were being caught by Norwegian purse seiners in the northeastern Atlantic Ocean during the 1950s.
4.4.2 Old-type seiners
Historically, there are two major types of purse-seining for tunas, single-boat seining and double-boat seining. Double-boat seining started much earlier than single-boat seining, but single-boat seining is now predominant.
4.4.3 Modern seiners
The following events during the 1950s contributed to the development of the modern purse-seine fishery for tunas: invention of the hydraulic power block, which facilitated handling of the net; availability of synthetic netting, which did not deteriorate even in the tropics; and, better facilities for freezing the fish (Orange and Broadhead, 1959; McNeely, 1961). The power block made it possible to retrieve larger nets in less time and reduced significantly the possibility of fish escaping from the bottom of the net. As the catch rates of purse seiners were greater than those of pole-and-line vessels, purse seining rapidly replaced pole-and-line fishing in the eastern Pacific Ocean during the late 1950s and early 1960s (although small numbers of pole-and-line vessels continued to fish in that area through the rest of the 20th century). In the Atlantic Ocean the purse-seine fishery for tropical tunas began in the Gulf of Guinea area in 1964, using vessels similar to those of the eastern Pacific Ocean. However, purse seining did not supplant pole-and-line fishing as much as it had in the eastern Pacific Ocean.
Schools of medium to large yellowfin are frequently associated with dolphins in the tropical eastern Pacific Ocean, and fishers took advantage of this relationship by herding the dolphins, with the tuna, into the net, after which they released the dolphins and retained the tuna (Perrin, 1969). The catch rates were high, and, since the market prices of yellowfin were greater than those for skipjack, this type of fishing was attractive to vessels large enough to use the equipment necessary for fishing for yellowfin associated with dolphins.
4.4.4 Growth of the purse-seine fleet
In 1966 the Inter-American Tropical Tuna Commission (IATTC) adopted a TAC for yellowfin tuna. The regulation allowed a vessel that left port before the TAC took effect to fish freely until the end of that trip. This triggered an increase in carrying capacity of the vessels, resulting in a significant increase in the total capacity of the purse-seine fleet.
Unfortunately, fishing for tunas associated with dolphins resulted in mortality of dolphins that were not able to escape from the nets. The United States adopted the Marine Mammal Protection Act (MMPA), the objective of which was to eliminate or minimize the mortality of marine mammals caused by the fishery for tunas (Joseph, 1994). Consequently, some United States vessels were sold to owners in other countries, and some transferred their operations to other areas, mainly the western and central Pacific Ocean. Also, new vessels were constructed for owners in other countries.
In the western and central Pacific Ocean Japanese two-boat purse seiners, using deeper and longer nets, had been fishing for tunas since the 1960s. Since the thermocline is deeper in the western Pacific than in the eastern Pacific, the United States vessels that transferred their operations there had to use deeper, faster-sinking nets.
Purse-seine fishing developed rapidly in the Atlantic Ocean during the 1970s, mostly by Spanish and French vessels; but also by vessels of the United States, Canada and the Soviet Union. Also, there were some FOC vessels with French or Spanish captains and crews.
Purse-seine fishing by European vessels based in the Seychelles began in the western Indian Ocean during the 1980s, and developed rapidly.
During the mid-1980s (particularly in 1984), the catch rates in the eastern Atlantic Ocean declined sharply, while those in the western Indian Ocean remained high. As a result, many European purse seiners transferred their operations from the Atlantic to the Indian Ocean. By that time, United States purse seiners were no longer fishing in the eastern Atlantic. Development of the Indian Ocean fishery and a subsidy program for construction of fishing vessels adopted by the European Community (EC), led to expansion of the European purse-seine fleet. Although a licensing system was in effect for the EC, when a new vessel entered the fishery, the registration of the one that it replaced was changed, but the vessel remained in the fishery. At the same time, introduction of various equipment (e.g. bird radar and select-call radio buoys in the 1980s and radio buoys and GPS tracking in the 1990s; see Section 2), increase in the size of the vessels and accumulated experience have led to greater fishing efficiency.
Many newcomers entered the purse-seine fisheries for tunas during the 1990s. Vessels of the Republic of Korea and the Taiwan Province of China began fishing in the western and central Pacific Ocean, and these fleets are still growing. Many other Central and South American countries began fishing for tunas in the eastern Pacific Ocean. Some of these were bought from owners in the United States, some were constructed for owners in Latin America, and some fly FOCs. FOC vessels are also very common in the Atlantic and Indian Oceans. To some extent, this reflects the desire of island nations in the western and central Pacific Ocean and coastal developing states in the Indian Ocean to participate in purse seining for tunas. At the time this is written, no purse-seine fleets have been identified as IUU fleets.
4.4.5 Fish-aggregating devices
Schools of tuna frequently associate with flotsam, such as tree parts and lumber lost or discarded at sea (Le Gall, Cayré and Taquet, 2000). Purse-seine fishers have taken advantage of this association by searching for flotsam and making sets around or near the flotsam when there are sufficient amounts of associated fish. This method of fishing was originated in the eastern Pacific Ocean during the 1960s, and has been a major part of the fishing operations in the western and central Pacific Ocean since the 1970s. When fishers found a piece of flotsam they sometimes attached a reflector or a radio buoy to it to assist them in locating it later.
Fishers then began to construct artificial fish-aggregating devices (FADs). Anchored FADs have been used in the western Pacific Ocean for many years by Philippine and Japanese fishers, and further experiments were conducted in the Pacific and Indian Oceans during the 1980s. Drifting FADs were used on a larger scale in the Atlantic Ocean during the early 1990s and shortly thereafter in the Pacific and Indian Oceans. Sophisticated methods of fishing and the use of ancillary vessels began during the 1990s. In the Atlantic about 60 percent of operations are on FADS in recent years, 89 percent (1999) in the East Central Pacific, and 79 percent (1999) in the Indian. In the eastern Pacific Ocean in 2003 19 percent of the sets were made on floating objects, and 86 percent of those sets were made on FADs. The vast majority of the FAD sets in the eastern Pacific Ocean are made between 10°N and 15°S.
Fishing on floating objects, including FADs, is often more profitable than other types of fishing, as the catch rates are higher and the expenditures for fuel and vessel maintenance are less. The sizes of individual yellowfin and bigeye tend to be less than those of yellowfin and bigeye caught by other types of purse-seine sets and much less that those of yellowfin and bigeye caught by longliners. Also, the bycatches of species other than tunas, such as sharks, dorado and wahoo, many of which are of commercial value to other fishers, are greater in floating-object sets than in other types of sets. The recent increases in the catches of bigeye by purse-seine gear are almost entirely the result of fishing for tunas associated with floating objects. In order to reduce the catches of these small fish, voluntary and mandatory restrictions on FAD fishing have been in force in the eastern Atlantic Ocean (since 1997), in the Indian Ocean (in 1998 only) and in the eastern Pacific Ocean (in 2001 only).
4.5 The pole-and-line fishery
The proportion of the catch of the principal market species of tunas by pole-and-line gear decreased from about 50 percent in 1950 to about 10 percent in 2000 (Figure 7). However, the total catches increased from the early 1950s to the mid-1970s, and then leveled off (Figure 10). The distributions of the catches of all species combined by pole-and-line vessels during representative years of the 1960s, 1970s, 1980s and 1990s are shown in Appendix 2, Figure 3, and those for the individual species for 1998 are shown in Appendix 2, Figure 4.
The catches of the principal market species of tunas by pole-and-line gear exceeded those of any other gear during the 1950s, but have been about equal to those of longliners since about 1960 and less than those of purse seiners since the late 1970s (Figure 3). The pole-and-line catches increased sharply during the early 1970s, and then stabilized at about a half million tonnes after 1975. Pole-and-line vessels now take only about 10 percent of the catch. Skipjack is, by far, the most important species in the pole-and-line fishery (Figure 10). However, pole-and-line vessels take a considerable portion of the total catch of albacore.
4.5.2 Traditional fisheries
Pole-and-line fishing has been conducted, at least since the 19th century. There are two types of fishing, the Portuguese style, which originated in the Madeira Islands, and the Japanese style, which originated in southern Japan. Each keeps live bait aboard the vessel to attract the fish and uses pole-and-line gear to catch them. In the Portuguese style the fishers stand in racks outside the stern of the vessel, while in the Japanese style the fishers stand on the deck on the port side of the vessel. Pole-and-line fishing has spread all over the world. The Portuguese style of fishing still takes place in Angola, Senegal, the west coast of Americas and northern Brazil, while Japanese style of fishing is practiced in Ghana, southern Brazil and the Taiwan Province of China.
4.5.3 Historical developments
During the 1950s pole-and-line fishing was the predominant method of fishing for tunas. There were important fisheries in the Bay of Biscay (for albacore and bluefin), near various islands in the eastern Atlantic Ocean (e.g. Madeira, where bigeye were caught), the northwestern Pacific Ocean (for albacore) and the tropical eastern Pacific Ocean (for yellowfin and skipjack). During the late 1950s pole-and-line vessels that had been fishing in the Bay of Biscay moved their operations to Senegal and the Congo. As mentioned previously, purse-seine vessels almost entirely replaced pole-and-line vessels in the eastern Pacific Ocean during the late 1950s and early 1960s. In the western Pacific Ocean, due to the greater depth of the thermocline, the initial attempts at purse seining were not very successful. Accordingly, the pole-and-line fishery continued, and the numbers of vessels and the catches even increased. Most of the technological innovations described in Section 2 originated in this western Pacific fishery during the 1960s, the 1970s and even the 1980s. In particular, perfection of systems of closed circulation of refrigerated sea water for the bait tanks made further expansion of the fishing grounds possible.
During the late 1960s Japan began foreign-based pole-and-line operations in the central South Pacific (for skipjack and albacore) and in Gulf of Guinea (for skipjack and yellowfin). In addition, vessels based in Japan participated in these fisheries. During the 1970s Japanese pole-and-line vessels began to withdraw from the Gulf of Guinea fishery, but they were replaced by Korean, and later by Ghanaian, pole-and-line vessels. The Japanese vessels that were withdrawn from the Gulf of Guinea fishery started a new fishery off the southern Brazil. A few years later, during the mid-1970s, Portuguese fishermen started a pole-and-line fishery based in Rio de Janeiro, Brazil. More recently, local pole-and-line fisheries have developed in many places, including Indonesia, the Philippines, Namibia and South Africa.
A new fishing method, which uses a non-fishing vessel carrying live bait as a floating object to attract and maintain fish schools and two pole-and-line vessels to catch the fish, was developed in Senegal during the late 1980s (Fonteneau and Diouf, 1994). This method was introduced to the Canary Island pole-and-line fishery during the mid-1990s.