The state of world highly migratory, straddling and other high seas fishery resources and associated species. FIGURE 22 Blue shark (Prionace glauca)

Transcription

1 24 The state of world highly migratory, straddling and other high seas fishery resources and associated species Catch (thousand tonnes) 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 FIGURE 22 Blue shark (Prionace glauca) FIGURE 23 Catches of requiem sharks (family Carcharhinidae) as reported to FAO Sharks - Carcharhinidae Pacific Ocean Indian Ocean Atlantic Ocean sharks, recorded catches total only 187 tonnes in 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 tonnes were recorded. Catches of requiem sharks (Figure 23) reported to FAO were less than tonnes in the 1950s, increasing to 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 tonnes in 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 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.

2 Highly migratory species 25 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 tonnes in FIGURE 24 Scalloped hammerhead sharks (Sphyrna lewini) FIGURE 25 Catches of hammerhead, bonnethead and scoophead sharks (family Sphyrnidae) as reported to FAO 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).

3 26 The state of world highly migratory, straddling and other high seas fishery resources and associated species FIGURE 26 The great white shark (Carcharodon carcharias) FIGURE 27 Geographic distribution of the great white shark (Carcharodon carcharias) (from Compagno, 2001) FIGURE 28 Shortfin mako shark (Isurus oxyrinchus) 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 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 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.

4 Highly migratory species 27 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 FIGURE 29 Geographic distribution of the shortfin mako shark (Isurus oxyrinchus) (from Compagno, 2001) FIGURE 30 Longfin mako shark (Isurus paucus) FIGURE 31 Geographic distribution of the longfin mako shark (Isurus paucus) (from Compagno, 2001) 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

5 28 The state of world highly migratory, straddling and other high seas fishery resources and associated species FIGURE 32 Salmon shark (Lamna ditropis) FIGURE 33 Geographic distribution of the salmon shark (Lamna ditropis) (from Compagno, 2001) FIGURE 34 Porbeagle shark (Lamna nasus) 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

6 Highly migratory species 29 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 tonnes in the mid-1950s to almost tonnes in 1963 (Figure 36). More recently, reported catches have Catch (thousand tonnes) FIGURE 35 Geographic distribution of the porbeagle shark (Lamna nasus) (from Compagno, 2001) FIGURE 36 Catches of mackerel sharks (family Lamnidae) as reported to FAO Sharks - Lamnidae Southern Ocean (negligible) Pacific Ocean Indian Ocean (negligible) Atlantic Ocean increased steadily from about tonnes in the early-1980s to almost tonnes in 2004, mostly shortfin mako (5 000 tonnes) and porbeagle (1 000 tonnes) sharks 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

7 30 The state of world highly migratory, straddling and other high seas fishery resources and associated species 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 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 10% of the highly migratory oceanic sharks are moderately exploited, 35% fully exploited, 40% overexploited and 15% depleted 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.

8 Highly migratory species 31 TABLE 2 Summary of the state of exploitation of highly migratory oceanic sharks Species/stocks Catches (tonnes) State of exploitation 2 Bluntnose sixgill shark (Hexanchus griseus) N Basking shark (Cetorhinus maximus) O-D Thresher shark (Alopias pelagicus) N/A N/A N/A N/A N/A F-O Thresher shark (Alopias superciliosus) F-O Thresher shark (Alopias vulpinus) F-O Thresher shark (Alopias spp.) Whale shark (Rhincodon typus) N/A N/A N/A N/A N/A F Requiem shark (Carcharhinus falciformis) Whitetip shark (Carcharhinus longimanus) N - M N Blue shark (Prionace glauca) N Winghead shark (Eusphyra blochii) N/A N/A N/A N/A N/A N Scalloped bonnethead (Sphyrna corona) Whitefin hammerhead (Sphyrna couardi) Scalloped hammerhead (Sphyrna lewini) N/A N/A N/A N/A N/A N N/A N/A N/A N/A N/A N F-O Scoophead (Sphyrna media) N/A N/A N/A N/A N/A N Great hammerhead (Sphyrna mokarran) N/A N/A N/A N/A N/A N Bonnethead (Sphyrna tiburo) N/A N/A N/A N/A N/A N Smalleye hammerhead (Sphyrna tudes) Smooth hammerhead (Sphyrna zygaena) N/A N/A N/A N/A N/A N N Sphyrnidae Great white shark (Carcharodon carcharias) Shortfin mako (Isurus oxyrinchus) Longfin mako (Isurus paucus) Salmon shark (Lamna ditropis) 2 4 D M-F-O N N/A N/A N/A N/A N/A F-O Porbeagle (Lamna nasus) O-D 1 Catch data from FAO FISHSTAT Plus 2 Symbols: 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 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

9 32 The state of world highly migratory, straddling and other high seas fishery resources and associated species Catch (thousand tonnes) FIGURE 37 The Atlantic pomfret (Brama brama) FIGURE 38 Catches of pomfrets and ocean breams as reported to FAO Pomfrets and ocean breams Pacific Ocean Atlantic Ocean 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 tonnes in 2001, from 18 countries fishing in the Atlantic and Pacific Oceans, but in 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 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

10 Highly migratory species 33 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 tonnes and 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 tonnes were reported in 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. Catch (thousand tonnes) FIGURE 39 The Pacific saury (Cololabis saira) FIGURE 40 Geographic distribution of the Pacific saury (Cololabis saira) (from Eschmeyer, Herald and Hammann, 1983) FIGURE 41 Catches of sauries as reported to FAO Sauries Pacific Ocean Atlantic Ocean (negligible) Dolphinfish 100 The two dolphinfishes of the Coryphaenidae family, 0 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)

11 34 The state of world highly migratory, straddling and other high seas fishery resources and associated species Catch (thousand tonnes) FIGURE 42 The common dolphinfish (Coryphaena hippurus) FIGURE 43 Geographic distribution of the common dolphinfish (Coryphaena hippurus) (modified from Collette, 1999) FIGURE 44 Catches of dolphinfish as reported to FAO Dolphinfish Pacific Ocean Indian Ocean 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 tonnes in 1950 to almost tonnes in the early-2000s (Figure 44). Slightly more than tonnes were reported in 2003 and Seven reporting entities have consistently declared landings since 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 State of other highly Atlantic Ocean 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

12 Highly migratory species 35 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 Species/stocks Catches State of exploitation 2 Pomfrets (several species) M-F Sauris (several species) N(M-F?) Dolphinfish (Coryphaena spp.) N(M-F?) 1 Catch data from FAO FISHSTAT Plus 2 Symbols: N = Not known; U = Underexploited; M = Moderately exploited; F = Fully exploited; O = Overexploited; D = Depleted; R = Recovering.