24 The state of world highly migratory, straddling and other high seas fishery resources and associated species 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 sharks, recorded catches total Blue shark (Prionace glauca) 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 FIGURE 23 bottom trawls near the coasts. Catches of requiem sharks (family Carcharhinidae) In 2004 more than 36 000 as reported to FAO tonnes were recorded. Catches of requiem sharks 100 (Figure 23) reported to FAO Sharks - Carcharhinidae 90 were less than 10 000 tonnes Pacific Ocean 80 in the 1950s, increasing to 40– ) Indian Ocean 50 000 tonnes in the 1960s and 70 Atlantic Ocean 1970s. After a brief decline 60 in the early-1980s, reported catches have increased more 50 or less steadily to more 40 than 87 000 tonnes in 2004. h (thousand tonnes (thousand h 30 Catches are reported from the Catc Atlantic, Indian and Pacific 20 Oceans with blue shark, 10 spot-tail shark (Carcharhinus 0 sorrah, a coastal non-oceanic 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 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. 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 FIGURE 24 mobile and in part migratory, Scalloped hammerhead sharks (Sphyrna lewini) 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 FIGURE 25 on light longline gear. Given Catches of hammerhead, bonnethead and scoophead sharks its life-history characteristics, (family Sphyrnidae) as reported to FAO 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). 26 The state of world highly migratory, straddling and other high seas fishery resources and associated species FIGURE 26 The great white shark The great white shark (Carcharodon carcharias) (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 FIGURE 27 to commercial fisheries, but Geographic distribution of the great white shark its sensitivity to harvest has (Carcharodon carcharias) (from Compagno, 2001) 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 FIGURE 28 29) is a coastal and oceanic Shortfin mako shark (Isurus oxyrinchus) 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. Highly migratory species 27 The longfin mako FIGURE 29 (Isurus paucus) (Figures 30 Geographic distribution of the shortfin mako shark and 31) is an oceanic, warm (Isurus oxyrinchus) (from Compagno, 2001) 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 FIGURE 30 still common is unknown), Longfin mako shark (Isurus paucus) 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 FIGURE 31 catch this species. Geographic distribution of the longfin mako shark The salmon shark (Lamna (Isurus paucus) (from Compagno, 2001) 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 28 The state of world highly migratory, straddling and other high seas fishery resources and associated species FIGURE 32 in the North Atlantic. The Salmon shark (Lamna ditropis) species is considered heavily fished even though