3. HIGHLY MIGRATORY SPECIES

As indicated above, highly migratory species are legally defined as those listed in Annex 1 of UNCLOS. They include tuna and tuna-like species, oceanic sharks, pomfrets, sauries and dolphinfish. Some of these species may only occur and/or be caught within EEZs but the available global database does not allow distinguishing between catches made on the high seas and those made within EEZs. Highly migratory species are therefore discussed without regard to stocks or occurrence within EEZs or on the high seas, except for tunas and some tuna-like species for which more detailed data are available.

3.1 Highly migratory tuna and tuna-like species

The information presented in this section is based primarily on the recent summary in FAO (2005a) and on the report of the FAO project on "Management of tuna fishing capacity: conservation and socio-economics" (FAO, 2005b). Information has also been obtained from Regional Fisheries Organizations, either directly or from their published reports and Web sites. In particular, updated information has been obtained from the Web pages of the Commission for the Conservation of Southern Bluefin Tuna (CCSBT, http://www.ccsbt.org/), the Inter-American Tropical Tuna Commission (IATTC, http://www.iattc.org/), the International Commission for the Conservation of Atlantic Tunas (ICCAT, http://www.iccat.es/), the Indian Ocean Tuna Commission (IOTC, http://www.iotc.org/) and the Secretariat of the Pacific Community (SPC, http://www.spc.org.nc/), their publications, or through submissions they have made to FAO specifically for the review Conference on the Fish Stock Agreement.

3.1.1 The resources

All highly migratory tuna and tuna-like species (billfishes, bonitos, mackerels and tunas) belong to the sub-order Scombroidei. The tunas (Thunnini) include the most economically important species referred to as principal market tunas because of their global economic importance and their intensive international trade for canning and sashimi. Tunas are sub-classified into four genera (Thunnus, Katsuwonus, Euthynnus and Auxis) with fourteen species all together.

The tunas included in Annex 1 of UNCLOS are in the order they are listed:

• Albacore tuna (Thunnus alalunga), which occurs in tropical and temperate waters worldwide.

• Bluefin tuna (Thunnus thynnus), mostly found in temperate waters of the Atlantic, including the Mediterranean, and Pacific Oceans. It is noted that since the adoption of UNCLOS, bluefin tuna in the northern Pacific has been identified as a different species, Pacific bluefin tuna (Thunnus orientalis) while bluefin in the Atlantic has been re-named Atlantic bluefin tuna.

• Bigeye tuna (Thunnus obesus), found in the Atlantic (but absent from the Mediterranean), Indian and Pacific Oceans.

• Skipjack tuna (Katsuwonus pelamis) with a worldwide distribution in tropical and temperate waters.

• Yellowfin tuna (Thunnus albacares), also with a worldwide distribution in tropical and sub-tropical more temperate seas, but absent from the Mediterranean.

• Blackfin tuna (Thunnus atlanticus) found in the western Atlantic in tropical and warm seas.

• Little tuna (Euthynnus alleteratus and E. affinis), with E. alleteratus found in tropical and subtropical waters of the Atlantic, including the Mediterranean, the Black Sea, the Caribbean Sea and the Gulf of Mexico, and E. affinis in the Indian and Pacific Oceans. It is noted that presently, E. alleteratus is called little tunny and E. affinis is called kawakawa.

• Southern bluefin tuna (Thunnus maccoyii), in temperate waters of the southern hemisphere in the Atlantic, Indian and Pacific Oceans.

• Frigate mackerel (Auxis thazard and A. rochei) found in the Atlantic (including the Mediterranean Sea where only A. rochei is found), Indian and Pacific Oceans. It is noted that presently, A. thazard is referred to as frigate tuna and A. rochei as bullet tuna.

The above tuna species listed as highly migratory species in Annex 1 of UNCLOS have extensive distribution on the high seas. Although their total catches amount to less than 5 percent of the total world marine fish catches, their landed value has been estimated to account for nearly 20 percent of the global marine total.

Tuna species can be loosely categorized into tropical and temperate tunas. They exhibit a wide range of life histories, ranging from the skipjack tuna, which has a short lifespan, high fecundity and wide distribution in tropical and temperate waters, to the bluefin tuna which is long lived, breeds late and has well-defined breeding and migration patterns. Differing life histories result in contrasts in vulnerability to overfishing. Skipjack are generally considered to be more resilient to exploitation, while bluefin are considered more vulnerable, all the more because of their extremely high market value. The other species have life history characteristics that are intermediate between those two extremes.

The tuna - like species included in Annex 1 of UNCLOS also have an extensive geographical distribution. These are:

• Marlins, of which there are eight species (Tetrapturus angustirostris, T. belone, T. pfluegeri, T. albidus, T. audax, T. georgei, Makaira indica, M. nigricans), with one or more species found in every Ocean. It is noted that presently, species of the genus Tetrapturus are referred to as spearfishes. It is also noted that the blue marlin species (Makaira nigricans and M. mazara) have been recently consolidated in one single species named Makaira nigricans (Buonaccorsi et al., 1999; Graves and McDowell, 1995). Changes have been already implemented in the FAO capture database and species list - Aquatic Sciences and Fisheries Information System (ASFIS) and accepted by all members of the Coordinating Working Party on Fishery Statistics (CWP) (L. Garibaldi, personal communication, 2006).

• Sailfishes, with two species (Istiophorus platypterus and I. albicans). I. platypterus was formerly restricted to the Indian and Pacific Oceans, but is now found in the Mediterranean Sea where it entered via the Suez Canal. I. albicans is found in the Atlantic Ocean and migrates into the Mediterranean Sea.

• Swordfish (Xiphias gladius) found in the Atlantic, Indian and Pacific Oceans, the Mediterranean Sea, the Sea of Marmara, the Black Sea and the Sea of Azov.

Little tunny (E. alleteratus) and kawakawa (E. affinis), and to some extent, blackfin tuna (T. atlanticus), black skipjack (E. lineatus), bullet tuna (A. rochei) and frigate tuna (A. thazard), are less oceanic and more associated with the continental shelves than the other tunas and tuna-like species in Annex 1 of UNCLOS. The general distribution and the location of the main fishing grounds of all the highly migratory tuna and of the main tuna-like species mentioned above are shown in Figures 3 and 4.

The longtail tuna (T. tonggol) is also an important tuna, not included in UNCLOS Annex 1, which has a wide but less oceanic distribution associated with the continental shelves. Other important tuna-like species not in Annex 1 of UNCLOS include slender tuna (Allothunnus fallai), butterfly kingfish (Gasterochisma melampus), wahoo (Acanthocybium solandri), bonitos (Cybiosarda, Orcynopsis and Sarda), and species of the genus Scomberomorus (Spanish mackerel, king mackerels, seerfish and sierra). Slender tuna and butterfly kingfish (with a circumpolar distribution in the Southern Ocean) are now caught mostly as bycatch of the longline fishery targeting southern bluefin tuna. In line with the definitions in UNCLOS and FSA, these species are therefore to be considered as straddling stocks or as high seas stocks if/when occurring only in the high seas.

3.1.2 The fisheries

Tuna fisheries are among the oldest fisheries in the world (FAO, 2005b) with Phoenician trap fisheries (Ravier and Fromentin, 2001) for bluefin tuna occurring around 2000 BC. They are mentioned by Aristotle, Oppian and Pliny the Elder, and they are also recorded in excavations at prehistoric sites. Until the second part of the twentieth century, fishing occurred mostly in coastal areas. As a result of increasing demand for tuna for canning, industrial fisheries began during the 1940s and 1950s. During the 1950s, the major industrial fisheries were the Japanese longline fishery and the pole-and-line fisheries of the United States of America and Japan, which operated in the Pacific Ocean. The longline fishery reached the Atlantic Ocean during the late- 1950s. Also, some European pole-and-line vessels, based in local ports, began fishing off the west coast of Africa at that time.

During the 1960s, European pole-and-line and purse-seine vessels began fishing for tunas in tropical areas off West Africa. Japanese pole-and-line vessels increased and expanded their area of operation in the western and central Pacific. Japanese longliners also expanded their fishing operations all over the world, targeting mostly albacore and yellowfin for canning. During the mid-1960s, vessels of the Republic of Korea and Taiwan Province of China became involved in large-scale longline fishing for tunas. At the end of the decade, improvements in freezing technology and cold storage systems developed for Japanese longliners, making it possible to produce fish that was acceptable for the sashimi market, which, in turn, led the vessels to shift their target species from yellowfin and albacore for canning to bluefin and bigeye for sashimi. In the eastern Pacific Ocean, the pole-and-line vessels of the United States of America were almost completely replaced by purse-seine vessels. Quotas for yellowfin in that region were first established in 1966.

During the 1970s the European purse-seine fishery in the tropical eastern Atlantic developed quickly while the United States of America purse-seine fishery of the tropical eastern Pacific expanded offshore. In the tropical eastern Pacific a number of vessels of the United States of America either changed flags to Central and South American countries to avoid the national regulations aimed at reducing the incidental mortality of dolphins or shifted their fishing effort to the western and central Pacific Ocean, where the association of yellowfin with dolphins was not important.

A purse-seine fishery for tunas began in the western Indian Ocean during the 1980s, when European vessels, which had fished in the Atlantic Ocean until then, moved to that area. In the Pacific Ocean the purse-seine fishery further expanded its fishing area, particularly in the western and central Pacific Ocean. In the Atlantic, countries such as Brazil and Venezuela entered the purse-seine fisheries. During the same period, the numbers of Japanese and Korean large-scale longliners began to decrease, whereas the fleet of Taiwan Province of China, and the numbers of vessels reflagged to countries of open registry increased rapidly.

Purse seiners began fishing with artificial fish-aggregating devices (FADs) in the Atlantic Ocean early in the 1990s, and the method quickly spread to the Indian and Pacific Oceans. Fisheries management became more active and intensified during the 1990s and continues to be more active in response to stock concerns and increasing focus on illegal, unreported and unregulated (IUU) fishing. The catch by small-scale coastal longline fisheries increased greatly during the 1990s. Another important event was the development of bluefin tuna farming which can have a significant effect in increasing fishing pressure on the wild stocks, particularly by targetting on young individuals.

Tuna are fished, traded, processed and consumed globally. The industrial fleets often transfer their operations from one ocean to another in response to changing conditions either in fish availability, markets, and/or fishing regulations, which makes it difficult to manage fishing capacity solely on a regional scale. In addition, the fish caught are frequently transported to other parts of the world for processing. Also, substantial IUU fishing, which occurs in all oceans in spite of recent efforts to control it, significantly complicates the management of the fisheries for tunas.

In 2004, tuna and tuna-like species classified as highly migratory in Annex 1 of UNCLOS accounted for 4.8 million tonnes, nearly 80 percent of the total reported catches of all tunas and tunalike species. Two species, skipjack tuna and yellowfin tuna accounted for nearly 60 percent of the catch (3.5 million tonnes) in that year. Not all the catches are from the high seas however, and the estimated portion caught outside EEZs varies from about 4 percent in the western central Pacific to almost 80 percent in the eastern Indian Ocean (Figures 5 and 6). In the Mediterranean, because countries have generally not declared EEZs, 100 percent of the catches are considered to be taken outside EEZs.

3.1.3 State of highly migratory tuna and tuna-like stocks

This section classifies the state of exploitation of stocks of tuna and tuna-like species according to the FAO classification scheme described in section 2.2 and their state of exploitation of this species group, based on the most recent information available, is summarized in Table 1. The main sources of information are the recent FAO summaries (FAO, 2005a; 2005b). Additional information was obtained from the Commission for the Conservation of Southern Bluefin Tuna (CCSBT), the Inter- American Tropical Tuna Commission (IATTC, 2005), the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Indian Ocean Tuna Commission (IOTC) and the Secretariat of the Pacific Community (SPC).

FIGURE 6 Catches of all highly migratory tuna and tuna-like species for all fishing gears, 2000 - 2004

TABLE 1
Summary of the state of exploitation of highly migratory tuna and tuna-like species by major ocean area

¹ Catch data by stock area from Carocci and Majkowski (2005), unless otherwise stated

² Catch data from FAO FISHSTAT Plus

³ Include Atlantic sailfish (I. albicans) and longbill spearfish (T. pluefgeri)

⁴ Include Frigate tuna (A. thazard), bullet tuna (A. rochei), kawakawa (E.affinins), little tunny (E. alleteratus) black skipjack (E. lineatus) and blackfin tuna (T. atlanticus)

⁵ Symbols: N = Not known; U = Underexploited; M = Moderately exploited; F = Fully exploited; O = Overexploited; D = Depleted; R = Recovering

Most highly migratory tropical tunas have very high fecundity, wide geographic distribution, opportunistic behaviour and other characteristics that make them highly productive and resilient to exploitation. With proper management, they are capable of sustaining high yields, but possibilities of overexploitation and stock depletion nevertheless exist if fishery management is not adequate. Highly migratory temperate tunas have life history characteristics that make them much more sensitive to exploitation. As a result, their expected yields are lower and the risks of overexploitation are higher making it all the more important to exercise prudent management.

Bluefin tuna, a temperate species most desired for sashimi, is depleted in the western Atlantic, as is southern bluefin tuna, and it is overexploited in the eastern Atlantic. The Pacific bluefin is fully exploited.

Albacore, another temperate species, is used mostly for canning. The stocks are fully exploited in the South Atlantic as well as in the North and South Pacific and overexploited in the North Atlantic. Albacore is probably moderately exploited in the Indian Ocean while the state of exploitation in the Mediterranean Sea is not known.

Although bigeye tuna, another species highly desired for sashimi, is tropical and has a life span shorter than bluefin, there is increasing concern that its exploitation may be too high. In addition to being overexploited, there is concern that increasing purse seine catches of small bigeye associated with FADs may negatively affect the longline catches of large bigeye, which have a much higher price. Bigeye tuna is overexploited in the eastern Pacific and is probably fully exploited elsewhere.

The yellowfin tuna stocks are close to or are being fully exploited in all oceans while skipjack tuna is only moderately exploited in the Pacific and probably also in the Indian Ocean. However, with the present fishing technique, catches of skipjack cannot be increased without undesired increases of catches of other species. In the Atlantic, the state of skipjack is uncertain.

The state of exploitation of many other tuna and tuna-like species is highly uncertain or unknown. Given the absence of reliable information on the state of exploitation, caution should be exercised in managing these fisheries, and it would not be prudent to allow fisheries to expand in the absence of further studies. Significant uncertainties in the state of exploitation of many billfishes represent a serious concern. In the Atlantic, blue and white marlins seem to be overexploited even though they are not generally targeted. Blue marlin is fully exploited in the eastern Pacific, but striped marlin is only moderately exploited. Because of commercial exploitation, there is more known on the state of swordfish exploitation than for other billfishes. In the Atlantic and the southeastern Pacific, swordfish are fully exploited, and there is concern about the effect of recent increases in fishing effort in the South Pacific. In the northeastern Pacific, swordfish is only moderately exploited. There is also concern about the intensification of fisheries targeting swordfish in the Indian Ocean.

In summary, the scientific information available primarily from regional tuna fishery management organizations and other intergovernmental organizations indicates that none of the tuna and tuna-like species are considered underexploited. For those stocks/species area combinations in Table 1 where the state of exploitation is known (24 out of 41, or 59 percent), 21 percent are moderately exploited, 50 percent are fully exploited, 21 percent are overexploited and 8 percent (southern bluefin and bluefin in the western Atlantic) are depleted. There are probably few opportunities to increase exploitation of these species, except in some areas of the Pacific, and possibly in the Indian Ocean, where significant increases in catches of skipjack tuna might be sustainable. However, if current fishing techniques are used, this can only be done at the expense of undesired increases in bycatch of other species, some of which may already be fully exploited or overexploited, and in need of tighter conservation measures.

The summary assessment provided above is essentially based on the reports of the scientific working groups of the relevant tuna fisheries management commissions and on publications by tuna experts. These assessments imply that 50 percent of the stocks are at or around 50 percent of their unfished biomass and 29 percent are well below that level. According to some other publications based on a crude analysis of a small part of the available catch and effort data, the state of tuna and tuna - like fishery resources would be much bleaker. For example, Myers and Worm (2003), examining data mostly from pelagic longline fisheries for highly migratory species, concluded that there had been a 90 percent decline in abundance of these species groups since the onset of the fishery. However, methodological flaws of the studies have been documented by Walters (2003), Hampton et al. (2005) and others (see http://imina.soest.hawaii.edu/PFRP/large_pelagics/large_pelagic_predators.html for more detailed information). Aside from methodological flaws, it is worth noting that most of the apparent declines occurred 50 years ago, when those fisheries started, and before management was instituted. The study also fails to mention that substantial declines (around 50 percent or more) from the unfished abundance are to be expected even for stocks exploited around their maximum biological productivity.

The high value of tuna, and the global nature of fleets and markets aggravate the concerns about excess fleet capacity and increased risk of overexploitation and stock depletion. In recent years, the World Tuna Purse-Seine Organization (WTPSO, an industry organization) temporarily limited fishing effort by their vessels in order to decrease the overall supply of fish to increase the price. Also, the number of longline vessels has been reduced in some countries. However, these actions are not regarded as sufficient in the long term to control fishing capacity and exploitation. Most of the regional tuna fishery management organizations are attempting to address the issue of tuna-fishing capacity in their areas of responsibility, in addition to the management of stocks through catch and fishing effort controls. However, the problem of managing tuna-fishing capacity is complex, involving biological, socio-economic and technological issues, whereas the conventions of most, if not all, of the tuna fishery management organizations do not address the social and economic aspects of fishery management.

Industrial tuna fleets are highly mobile and the principal market tunas are intensively traded on the global scale. In addition, many tuna research, conservation and management problems are similar in all oceans. Therefore, there is a need for exchange of information and for collaboration on the global scale regarding fisheries, fisheries research and fisheries management for tunas and other species with wide global distribution.

3.2 Highly migratory oceanic sharks

Sharks covered under this heading are those listed in Annex 1 of UNCLOS: Bluntnose sixgill shark (Hexanchus griseus), basking shark (Cetorhinus maximus), thresher sharks (family Alopiidae), whale shark (Rhincodon typus), requiem sharks (family Carcharhinidae), hammerhead, bonnethead, or scoophead sharks (family Sphyrnidae), and the mackerel sharks (family Lamnidae) (it is noted that in UNCLOS the family Lamnidae is listed as Isurida, using an old family name).

The total reported catches of species and families of sharks, listed in Annex 1 of UNCLOS, was close to 100 000 tonnes in 2004. The requiem sharks (Carcharinidae) account for 90 percent of these catches. However, the total catch and mortality of sharks (such as discarded bycatch) is likely to be much larger than the reported catch. Unfortunately, the state of many shark populations is unknown, or poorly known. However, the life history characteristics of sharks (e.g. slow growth, long life span, low fecundity) make them particularly vulnerable to overexploitation and depletion and therefore fisheries for such sharks should be managed with caution.

Due to the nature of the available information, this section dealing with oceanic sharks provides descriptions of resources, fisheries and their state of exploitation on a species by species, as well covering fisheries and state of exploitation separately. An FAO report (Castro, Woodley and Brudek, 1999) prepared in support of the International Plans of Action for Conservation and Management of Sharks, FAO catalogues (Compagno, 1984a; 1984b; 2001), other FAO sources, and Fishbase, provided information on the biological characteristics and geographical distribution of oceanic sharks. When available, drawings from the FAO databases and Species Identification Programme have been included in the text. This report intentionally gives greater emphasis in reviewing the biology of oceanic sharks than for tuna and tuna-like species, because the biology of the latter is more readily available in other reviews.

3.2.1 Bluntnose sixgill shark

Bluntnose sixgill shark (Hexanchus griseus) (Figures 7 and 8) has an almost circumglobal distribution in tropical and temperate seas on the continental and insular shelves and upper slopes at depths from surface to at least 1 875 m, but it is mostly a deep-water shark. It is locally common and taken by line gear, gillnets, traps and pelagic and bottom trawls, for use fresh, frozen, dried salted for human consumption, and for fishmeal and oil. It is also the subject of dive tourism on the Canadian Pacific coast. There are no assessment of the state of the stock(s) or exploitation. Catches have been reported only from the Atlantic Ocean since 2001 (one tonne) with up to 30 tonnes in 2004.

3.2.2 Basking shark

The basking shark (Cetorhinus maximus) (Figures 9 and 10), is a coastal-pelagic shark found in boreal to warm temperate waters of the continental and insular shelves, occurring from far offshore to near shore just beyond the surf zone. It occurs around all the continents except Antarctica and the Arctic. Surface basking in this shark is thought to be related to feeding on surface concentrations of food plankton, and courtship and mating, although the species is also known to feed on plankton aggregations in deep waters on the edge of continental shelves. Basking sharks undertake long-distance migrations.

The basking shark has been the target of harpoon fisheries from small boats, but it has also been taken in nets, including bottom gillnets and occasionally bottom and pelagic trawls. The species also interacts with other gears, causing gear damage and harming themselves in the process.

The basking shark has been exploited commercially for centuries in several parts of the world mainly for its liver oil, which was used as lighting fuel for lamps in the past, and during this century as a source of chemical compounds. Several localized basking shark fisheries have shown sharp declines recently and in the past, but it is difficult to separate natural fluctuations in local abundance from the effects of exploitation globally.

The basking shark are likely to be extremely vulnerable to overexploitation, perhaps more so than most sharks, and this can be ascribed to its slow growth rate, advanced age of maturity, long gestation period, low fecundity (like all sharks), and probable small size of existing populations. Reported catches in excess of 8 000 tonnes (Figure 11) were common during 1960 to 1980, but they have been much less since the end of the 1990s. In 2004, 239 tonnes were reported. The species is probably overexploited globally with some areas being depleted.

The basking shark is listed on Annex II to the Protocol "Endangered or Threatened Species" of the Barcelona Convention for the Protection of the Mediterranean Sea and in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). It is legally protected by several countries (such as UK, Malta, US Federal waters) and targeting basking sharks is prohibited in New Zealand.

3.2.3 Thresher sharks (family Alopiidae)

There are three species of thresher sharks (family Alopiidae): Alopias pelagicus, Alopias superciliosus and Alopias vulpinus. All three species are believed to occur in temperate and tropical waters of all oceans. Given their life-history characteristics, these species are not expected to have a high resilience to exploitation, but stock status remains uncertain. Unless demonstrated otherwise, it is prudent to consider these species as being fully exploited or overexploited globally.

Alopias pelagicus (Figures 12 and 13) was formerly exploited by longline fisheries in the northwestern Indian Ocean, but it is also fished in the Central Pacific. It is utilized for its meat (for human consumption), liver oil for vitamin-A extraction, hides for leather, and fins for sharkfin soup.

Alopias superciliosus (Figures 14 and 15), commonly known as the bigeye thresher shark, has been caught in the oceanic longline fisheries operating in the northwestern Indian Ocean, western and Central Pacific, eastern North Pacific and North Atlantic. This species is also taken as incidental bycatch in fixed bottom and pelagic gillnets and in trawls.

Alopias vulpinus (Figures 16 and 17) is frequently caught by offshore longline and pelagic gillnet fisheries. It is also fished with anchored bottom and surface gillnets, and it is a bycatch of other gear including bottom trawls and fish traps. The species became the object of an important targeted pelagic gillnet fishery off the west coast of the United States of America (particularly California, and also Washington and Oregon) in the late-1970s, with a peak reported catch of 1 000 tonnes in 1982 (not reported in FAO statistics), declining due to overfishing to less than 300 tonnes by the late-1980s. The targeted fishery was ended by 1990, but the species is still caught as bycatch of the swordfish gillnet fishery and may be sold for higher prices in the market than swordfish.

Catches of Alopiidae that have been reported to FAO since the early-1980s have generally been less than 1 600 tonnes (Figure 18) and around 1 000 tonnes since 1998 (972 tonnes in 2004). Apparently, not all catches are reported to FAO, given the 1 000 tonnes referred to in the paragraph above.

3.2.4 Whale shark (Rhincodon typus)

Whale shark (Rhincodon typus) (Figures 19 and 20) has a circumglobal distribution in tropical and warm temperate seas. It is an epipelagic oceanic and coastal pelagic species ranging from far offshore to close inshore, sometimes entering lagoons of coral atolls. It is generally encountered close to or at the surface, as solitary individuals or in aggregations of up to hundreds of sharks. Whale sharks migrate long distances, with their movements probably timed with plankton blooms and changes in water temperatures. They are often associated with schools of pelagic fish, especially scombrids. Whale sharks have been fished sporadically by some countries around the Indian and western Pacific Oceans, but no catches are recorded in the FAO fisheries statistics database.

Given its life-history characteristics, the whale shark is expected to have low resilience to exploitation, with most recent fisheries having collapsed or ceased due to legal protection, but the state of stocks remains uncertain in most areas. Unless demonstrated otherwise, it is prudent to consider the species as being fully exploited globally. Whale sharks are currently protected in several parts of the world: Western Australia, India, the Maldives, the Philippines, and in parts of the United States of America (Florida state waters and all federal waters of the Gulf of Mexico and Atlantic coast). The whale shark is listed on Appendix II of both the Convention on Migratory Species and CITES.

3.2.5 Requiem sharks (family Carcharhinidae)

Requiem sharks (family Carcharhinidae), have a worldwide distribution in tropical and temperate waters. There are 50 species in the family (30 in genus Carcharhinus) which is, by far, the most important shark family for fisheries in the tropics. The main species from a fisheries point of view are: Carcharhinus falciformis, Carcharhinus signatus, Carcharhinus longimanus, Carcharhinus sorrah and Prionace glauca. However, Carcharhinus sorrah is not an oceanic species and it is not considered further.

The silky shark (Carcharhinus falciformis) (Figure 21), has an oceanic and coastal, circumtropical distribution and most common offshore. It is an oceanic, epipelagic and littoral, tropical shark, found near the edge of continental and insular shelves, as well as far from land in the open sea, to depths of 500 m. It occasionally occurs inshore where the water is as shallow as 18 m. It is an active, quick-moving, aggressive shark. Its population dynamics and stock structure are poorly known. This is one of the three most common oceanic sharks, along with the blue shark (Prionace glauca) and oceanic whitetip shark (Carcharhinus longimanus), and one of the more abundant large marine organisms. It is very commonly taken by pelagic longline fisheries, and occasionally by fixed bottom nets. The state of exploitation is unknown. Its wide distribution and high abundance in most tropical shelves of the world suggests that presently there are no major concerns over the conservation of this species globally. The silky shark is at present relatively free of threats in the form of habitat destruction because it does not live inshore nor does it utilize coastal lagoons as pupping or nursery areas like other shark species. In 2004 slightly more than 4 000 tonnes were reported, but past catches have been considerably higher.

Whitetip shark (Carcharhinus longimanus), is an oceanic shark found in tropical and warm-temperate waters of the Atlantic, possibly in the Mediterranean Sea, in the western Indian Ocean and in the Pacific. It is usually found far offshore in the open sea but it sometimes occurs in water as shallow as 37 m inshore, particularly off oceanic islands or in continental areas where the shelf is very narrow. It is regularly caught with pelagic longlines, also handlines and occasionally pelagic and even bottom trawls. It is utilized fresh, smoked and dried salted for human consumption, for hides, for fins (processed into the ingredients for shark-fin soup), and for liver oil (extracted for vitamins) and fishmeal. Although it is one of the most common oceanic sharks, recorded catches total only 187 tonnes in 2004.

Blue shark (Prionace glauca) (Figure 22), has a worldwide distribution in temperate and tropical oceanic waters. It is one of the most abundant and the most heavily fished shark in the world, often as bycatch in pelagic longlines fisheries, but also on hook-and-lines, in pelagic trawls, and even bottom trawls near the coasts. In 2004 more than 36 000 tonnes were recorded.

Catches of requiem sharks (Figure 23) reported to FAO were less than 10 000 tonnes in the 1950s, increasing to 40 - 50 000 tonnes in the 1960s and 1970s. After a brief decline in the early-1980s, reported catches have increased more or less steadily to more than 87 000 tonnes in 2004. Catches are reported from the Atlantic, Indian and Pacific Oceans with blue shark, spot-tail shark (Carcharhinus sorrah, a coastal non-oceanic species taken primarily within EEZs) and silky shark being the most important species.

3.2.6 Hammerhead, bonnethead and scoophead sharks (family Sphyrnidae)

The family Sphyrnidae comprises nine species: the winghead shark (Eusphyra blochii), the scalloped bonnethead (Sphyrna corona), the whitefin hammerhead (Sphyrna couardi), the scalloped hammerhead (Sphyrna lewini), the scoophead (Sphyrna media), the great hammerhead (Sphyrna mokarran), the bonnethead (Sphyrna tiburo), the smalleye hammerhead (Sphyrna tudes), and the smooth hammerhead (Sphyrna zygaena). The members of the family are considered coastal; occasionally occurring in brackish water with a global distribution mostly in warm waters.

Although all species are caught, only the scalloped hammerhead and the smooth hammerhead are reported as individual species in the FAO statistics.

The smooth hammerhead (Sphyrna zygaena) was believed to be an amphitemperate species (i.e. occurs in temperate water in the northern and southern hemispheres, absent from the tropics), but it is now known to occur in the tropics. It has a circumglobal distribution. It is an active, common, coastal-pelagic and semi-oceanic species. It is caught with pelagic longlines, handlines, as well as bottom and pelagic trawls.

The scalloped hammerhead (Sphyrna lewini) (Figure 24) has essentially a circumglobal distribution in coastal and semi-oceanic warm temperate and tropical seas. It occurs over continental and insular shelves and in deep water adjacent to them, often approaching close inshore and entering enclosed bays and estuaries. Its depth range is from the intertidal at the surface to depths of about 275 m. It is probably the most abundant hammerhead. This species is apparently highly mobile and in part migratory, forming huge schools of small migrating individuals. Owing to its abundance, the species is common in inshore artisanal and small-scale commercial fisheries, as well as offshore operations. It is caught with pelagic longlines, fixed bottom longlines, fixed bottom nets, and even bottom and pelagic trawls. The young are easily caught on light longline gear. Given its life-history characteristics, the scalloped hammerhead shark is expected to have very low resilience to exploitation and fisheries for the species should be managed with great caution. Although its worldwide distribution and known high abundance gives the species some protection globally, the risk of local depletions remains a serious concern.

Catches of Sphyrnidae have been reported only from the Atlantic Ocean since 1991 (Figure 25). The catch was near 2 200 tonnes in 2004.

3.2.7 Mackerel sharks

Mackerel sharks (currently family Lamnidae, although UNCLOS Annex 1 refers to them as Isurida) have a worldwide distribution in temperate and tropical seas. There are five species in the Lamnidae family: the great white shark (Carcharodon carcharias), the shortfin mako (Isurus oxyrinchus), the longfin mako (Isurus paucus), the salmon shark (Lamna ditropis), and the porbeagle (Lamna nasus).

The great white shark (Carcharodon carcharias) (Figure 26 and 27), is mostly amphitemperate found in coastal and offshore areas of continental and insular shelves. Its depth range goes from the surface to below 1 000 m and individuals have been observed to cross ocean basins and enter deep tropical waters during migration (Bonfil et al., 2005). The great white shark is of little interest to commercial fisheries, but its sensitivity to harvest has led to its listing on CITES Appendix II in 2004. It is also listed on Annex II to the Protocol "Endangered or Threatened Species" of the Barcelona Convention for the Protection of the Mediterranean Sea, and protected by several countries including South Africa, Australia, United States of America, Malta.

The shortfin mako (Isurus oxyrinchus) (Figures 28 and 29) is a coastal and oceanic circumglobal species found in temperate and tropical waters, generally warmer than 16 °C. It occurs from the surface down to at least 150 m. The shortfin mako may be the fastest shark and one of the swiftest and most active fishes. This is an important species for longline fisheries where it occurs, because of its high quality meat. It is also a prime game fish prized by sport anglers. Given its life-history characteristics, the shortfin mako is expected to have medium resilience to exploitation (relative to other sharks). Its worldwide distribution and relatively high abundance in some areas probably means it is not currently at risk, but like all elasmobranch it can be easily overfished and localized depletion is always a risk. According to ICCAT (2005) the possibility that the biomass in the north Atlantic is below that producing Maximum Sustainable Yield (MSY) cannot be ruled out, but in the south Atlantic it is probably above.

The longfin mako (Isurus paucus) (Figures 30 and 31) is an oceanic, warm water, epipelagic species, probably circumtropical, but records are sporadic with the result that the distribution is poorly known. The species is probably often mistaken for the apparently far more common shortfin mako shark (Isurus oxyrinchus) or included with records for it. However, it was apparently common in the western Atlantic and possibly in the Central Pacific (whether it is still common is unknown), but rare elsewhere. It is probably taken regularly in tropical pelagic longline fisheries for tuna and swordfish as bycatch. In addition to longlines, the species is taken with hooks and lines and with anchored gillnets. Little is known about the state of longfin mako shark populations. Without such information, management should be cautious with fisheries that catch this species.

The salmon shark (Lamna ditropis) (Figures 32 and 33) is a common coastal-littoral, offshore and epipelagic shark, found in cool waters of the north Pacific, at depths from the surface to below 150 m. Salmon sharks are common in continental offshore waters but range inshore to just off beaches; they also are abundant far from land in the North Pacific Ocean basin. This species has been fished in the North Pacific in the past by oceanic longliners and offshore gillnetters. They are also caught in salmon seines, by salmon trollers towing hooks, and possibly by bottom trawlers off Alaska. They are occasionally trammel-netted by halibut fishermen off California and as bycatch in gillnets set for swordfish and thresher sharks off California. Sports anglers in Alaska and Canada catch salmon sharks using rod and reel much like porbeagle anglers in the North Atlantic. The species is considered heavily fished even though most of the catch is discarded bycatch. It has a negative image as an abundant and low-value pest that avidly eats or damages valuable salmon and wrecks gear, which encourages fishers to kill it. Knowledge of its biology is limited despite its abundance, but its fecundity is very low and the species probably cannot sustain current fishing pressure for extended periods.

The porbeagle (Lamna nasus) (Figures 34 and 35) is a coastal and oceanic, amphitemperate species, with its centres of distribution in the North Atlantic, and in a circumglobal band of temperate water of the southern Atlantic, southern Indian, southern Pacific and Antarctic Oceans. The porbeagle is most abundant on the continental offshore fishing banks, but it is also found far from land in ocean basins and occasionally close inshore. This shark usually occurs in cold water, less than 18 °C and down to 1 °C. The porbeagle is found at the surface down to depths of about 350 m or more, singly and in schools and feeding aggregations. Porbeagles may come inshore and to the surface in summer, and over winter offshore beneath the surface. Catches in Europe indicate that the porbeagle segregates by size (age) and gender. Porbeagles of the western North Atlantic seem to constitute a single stock that undertakes extensive migrations between southern Newfoundland (Canada) in summer to at least Massachusetts (USA) in the winter. Long-term tagging data suggest that there is no mixing between this population and that of the eastern North Atlantic. Porbeagles breed on both sides of the North Atlantic. This species has been heavily fished commercially and utilized for human consumption in the temperate North Atlantic and the Mediterranean, but is also caught as bycatch in the Southern Hemisphere (e.g. it is the second most common shark taken as bycatch of the New Zealand longline fishery).

Stocks in the North Atlantic have shown signs of serious overexploitation as indicated by a large decline in catch. The western Atlantic stock is currently considered overexploited. For the Northeast Atlantic, ICES (2005) concluded that the stock is depleted and no fishery should be permitted. In the past, porbeagles were considered a nuisance to commercial fishermen because they wrecked light gear set for bony fishes (such as cod nets) and bit fish off hooks. Porbeagle are an important bycatch of Japanese longliners and probably of the pelagic fishing fleets of other countries fishing in the southern Indian Ocean and elsewhere in the Southern Hemisphere, where information on catches is poor and may be little-utilized except for fins.

Reported catches of Lamnidae increased sharply from less than 2 000 tonnes in the mid-1950s to almost 10 000 tonnes in 1963 (Figure 36). More recently, reported catches have increased steadily from about 1 000 tonnes in the early-1980s to almost 6 500 tonnes in 2004, mostly shortfin mako (5 000 tonnes) and porbeagle (1 000 tonnes) sharks.

3.2.8 The fisheries

As highlighed in FAO (2000b), sharks are long-lived, slow-growing, and producing few offspring. These characteristics are associated with low productivity. They imply that the production of recruits is closely linked to the spawning stock of adults. Stock recovery should be expected to be slow in the event that overexploitation depletes stocks. The number of shark species is small compared with the number of species of bony fishes, but they occupy a variety of habitats from near shore to the ocean abyss. They are most numerous at depths less than 200 m in tropical and warm temperate marine habitats.

Shark fisheries pre-date recorded history, and every part of these animals has been used for some purpose. Shark meat is important food consumed fresh, dried, salted or smoked. In many communities fins of sharks are among the world's most expensive fishery products. Shark cartilage and other products are increasingly sought for medicinal purposes. Few fisheries use the whole animal however: some use only the meat, others only use the fins, or livers or skin. In the majority of cases where only a portion of the animal is used, the rest is discarded at sea, which makes species identification of the catch difficult.

Fisheries for sharks are common throughout the world and use a variety of fishing gears and vessels. Sharks are taken mainly by gillnet and hook or trawl in industrial and artisanal fisheries. Small amounts are taken in traditional and recreational fisheries (game fishers and divers) and in beach gillnet and drumline fishing as bather protection programmes. There are several fisheries directed at one or a small number of species of shark, but most sharks are taken in multispecies fisheries where the fishers tend to target more highly valued traditional bony fish species.

The following categories of shark fisheries can be identified: coastal hook and gillnet fisheries, demersal trawl bycatch fisheries, deep-water bycatch fisheries, pelagic bycatch fisheries (primarily bycatch in tuna longline and purse seine fisheries) and freshwater shark fisheries. Since most shark catch is taken as bycatch, most of the catch is reported as unidentified shark, mixed fish or is not reported at all. This lack of species identification of the catches and lack of information on fishing effort means basic data for fishery assessment are not available for most species.

An important concern about fisheries that catch sharks is that harvest strategies designed to maximize economic and social benefits from multi-species fisheries have a high probability of depleting the least productive species (such as sharks), unless methods for making fishing more selective (thus able to avoid overfishing vulnerable species like sharks) are developed and implemented. As fishing effort increases, older and larger individuals and larger species disappear from the assemblage to be replaced by smaller counterparts. This results in a gradual drift towards shorter-lived, fastergrowing species, which negatively effects biodiversity.

3.2.9 State of the highly migratory oceanic shark stocks

The state of the stocks has been described under each species. In general, sharks are vulnerable to overexploitation and depletion, especially locally. In the absence of stock specific information on the state of fisheries and fishery resources, it is prudent to consider the state of shark populations as being at least fully exploited, and to apply a precautionary approach to management. The general state of exploitation of oceanic sharks is summarized in Table 2, where it is shown that of the 33 species group-area combination, 13 are unknown (39 percent). Of the remaining 20, none are considered underexploited or recovering, 10 percent are considered moderately exploited, 35 percent fully exploited, 40 percent overexploited, and 15 percent depleted.

In terms of biomass, this implies that 35 percent of the stocks are at or around 50 percent of their unfished biomass and 55 percent are well below that level. As for tuna and tuna-like species, the status of oceanic sharks fishery resources has been described as being considerably worse (Baum et al., 2003; Baum and Myers, 2004). However, while agreeing that there have been declines in the populations of some species, the scientists involved in the assessments of northwest Atlantic and Gulf of Mexico sharks, conclude that the magnitude of the changes are smaller than those reported in the aforementioned publications (Burgess et al., 2005). Notwithstanding the divergence of views and as already stressed by FAO in the early-1990s (Garcia and Majkowski, 1992) the situation of world oceanic shark stocks is definitely a source of serious concern.

TABLE 2
Summary of the state of exploitation of highly migratory oceanic sharks

¹Catch data from FAO FISHSTAT Plus
²Symbols: N = Not known; U = Underexploited; M = Moderately exploited; F = Fully exploited; O = Overexploited; D = Depleted; R = Recovering.

3.3 Other highly migratory species

The species in this section, unlike tunas and to some extent sharks, have not attracted large or high profile fisheries. Therefore, there is little information about these species and their state of exploitation, other than reported catches and some information on their biological characteristics and geographical distribution, summarized in the FAO Species Identification and Data Programme (SIDP) Web site, Fishbase and other FAO information resources.

3.3.1 Pomfrets

The pomfrets (family Bramidae) include eight genera and 21 species. Annex 1 of UNCLOS refers to the family Bramidae without listing individual species. Thus all 21 species are considered highly migratory with respect to UNCLOS. The Bramidae is a family of pelagic, benthopelagic and bathypelagic fishes found in temperate and tropical waters of the Atlantic, Indian and Pacific Oceans. The main characteristic of most of the species is that they are oceanodromous, that is, they migrate within oceans typically between spawning and different feeding areas, with migrations being cyclical, predictable and covering more than 100 km.

The worldwide landings of pomfrets are poorly documented. The FAO fishery statistics database lists Atlantic pomfret (Brama brama) (Figure 37), Pomfrets, and ocean breams not elsewhere included (nei). The time series shows strong oscillations. Maximum landings were close to 18 000 tonnes in 2001, from 18 countries fishing in the Atlantic and Pacific Oceans, but in 2004 7 000 tonnes were recorded (Figure 38). Because pomfrets are mostly caught as a bycatch in other fisheries, there is very limited biological information on the species. Pomfrets are included in management plans in the United States of America and Australia, but they do not appear to be assessed by international fisheries bodies. Although their state of exploitation is not known, there is no indication of overexploitation. According to FAO (2005a), they appear to be fully exploited in the eastern Indian Ocean, and moderately exploited in the Southwest Pacific.

3.3.2 Sauries

Sauries belong to the Scomberesocidae family. The species included in Annex 1 of UNCLOS are the Atlantic saury (Scomberesox saurus), the Pacific saury (Cololabis saira), the saury (C. adocetus), and the king gar (Scomberesox saurus scombroides). The list contains three species and one subspecies belonging to one of the species cited. The species Scomberesox saurus has two subspecies: S. saurus saurus and S. saurus scombroides. It is therefore assumed that Scomberesox saurus in Annex 1 is Scomberesox saurus saurus. All these species are pelagic, schooling and oceanodromous.

The Atlantic saury (Scomberesox saurus saurus) lives near the surface in the North Atlantic, in the Baltic Sea and throughout the Mediterranean. The Pacific saury (Cololabis saira) (Figures 39 and 40), is widely distributed in the North Pacific. It is generally found offshore, usually near the surface and migrates seasonally. It is the object of a substantial fishery and is a popular fish in Japan. Most of the reported catches are from this species. The saury (C. adocetus), is a tropical species of the Eastern Pacific. The king gar (Scomberesox saurus scombroides) lives in brackish and marine waters, it is only of minor commercial importance and it occurs in the Atlantic, Indian and Pacific Oceans with circumglobal distribution in temperate waters of the southern hemisphere.

Only six countries have reported saury landings to FAO. Landings have fluctuated between 200 000 tonnes and 600 000 tonnes since 1950, without a clear long-term trend since the early-1970s (Figure 41). Japan accounts for 49 percent to 98 percent of the reported total landings. The Pacific saury accounts for more than 95 percent of the reported landings. Slightly more than 350 000 tonnes were reported in 2004.

Similar to pomfrets, sauries are included in national management plans in some countries but they are not a species of direct interest for international fisheries bodies. Although their state of exploitation is not known, sauries are unlikely to be overexploited.

3.3.3 Dolphinfish

The two dolphinfishes of the Coryphaenidae family, the common dolphinfish (Coryphaena hippurus) and the Pompano dolphinfish (Coryphaena equiselis), are included in Annex 1 of UNCLOS. Both species follow boats and associate with floating objects which may be used as attracting devices in fisheries.

The common dolphinfish (C. hippurus) (Figures 42 and 43) is generally common in most warm and temperate seas, at 21 to 30 ºC in the Atlantic (including the Mediterranean), the western and eastern Indian Ocean and in the western central Pacific. It is an epipelagic species (i.e. living or feeding in surface waters to depths of 200 m).

The Pompano dolphinfish (C. equiselis) has a worldwide distribution in tropical and subtropical seas. It is primarily an oceanic species but may enter coastal waters.

More than 40 countries reported dolphinfish landings to FAO (C. hippurus only). Reported landings show a sustained increasing trend from 7 000 tonnes in 1950 to almost 50 000 tonnes in the early-2000s (Figure 44). Slightly more than 50 000 tonnes were reported in 2003 and 2004. Seven reporting entities have consistently declared landings since 1950. The Pacific Ocean accounts for more than half of the catches, with Japan and Taiwan Province of China being by far the largest contributors. Some dolphinfish fisheries within EEZs are actively managed, sometimes using interesting spatial approaches (e.g. the lampuki fishery in Malta). Although the state of exploitation is not known, dolphinfish are unlikely to be overexploited.

3.3.4 State of other highly migratory fish stocks

As discussed above, the state of exploitation of other highly migratory species of pomfrets, sauries and dolphinfish is poorly known or not known, and in most cases there is not even reliable information on catches. Nevertheless, in some cases a more or less educated guess of the most likely state of exploitation is possible based on fragmented information on life history patterns, geographical distribution, and available catches. This information is summarized in Table 3. Pomfrets are moderately or fully exploited in the Indian Ocean, while the state of sauries and dolphinfish is unknown, but based on available information it seems unlikely that they are being overexploited. Thus, would be either moderately or fully exploited, although this will need to be confirmed, particularly prior to any further expansion of the exploitation.

TABLE 3
Summary of the state of exploitation of selected other highly migratory species

¹Catch data from FAO FISHSTAT Plus
²Symbols: N = Not known; U = Underexploited; M = Moderately exploited; F = Fully exploited; O = Overexploited; D = Depleted; R = Recovering.