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Dolphins, Whales and Porpoises: 2002-2010 Conservation - IUCN

Dolphins, Whales and Porpoises: 2002-2010 Conservation - IUCN

south of the Antarctic

south of the Antarctic Convergence in January (Kasamatsu and Joyce 1995). Long-finned pilot whales in the North Atlantic have long been exploited in drive fisheries as well as in shore-based and pelagic hunts. They are also commonly killed incidentally in gillnet, trawl, and longline fisheries. A drive fishery in Newfoundland considerably reduced the numbers of long-finned pilot whales in the western North Atlantic before it ceased in the early 1970s (Mercer 1975). The only area with a continuing large direct kill is the Faroe Islands, where the annual catch (by driving) increased from an average of about 1500 in the early 1970s to nearly 2500 in the 1980s, and declined to approximately 1000–1500 in the 1990s. Sighting surveys in 1987 and 1989 supported a population estimate of more than 750,000 pilot whales in the central and north-eastern North Atlantic (Buckland et al. 1993a). The removals by drive hunting at the Faroes have therefore been considered sustainable (NAMMCO 2000a). Risso’s dolphin, Grampus griseus Risso’s dolphins are abundant in tropical and temperate latitudes throughout the world’s oceans (Kruse et al. 1999) (Figure 18). They prey almost exclusively on squid. A recent study of habitat preferences in the northern Gulf of Mexico indicated that Risso’s dolphins occur mainly on steep sections of the upper continental slope (Baumgartner 1997). There are an estimated 29,000 off the eastern United States (Waring et al. 2001), 2700 in the northern Gulf of Mexico (Waring et al. 2001), 16,500 off the western United States (Carretta et al. 2001), 83,000 in three areas of concentrated occurrence off Japan (Miyashita 1993), and 175,000 in the eastern tropical Pacific (Wade and Gerrodette 1993). Risso’s dolphins are hunted regularly in Japan, with reported catches in recent years ranging from about 250–500 (see tables of catches of small cetaceans appended to annual reports of the Sub-committee on Small Cetaceans of the IWC’s Scientific Committee, published in the annual supplement of the Journal of Cetacean Research and Management). They are also a major target of artisanal hunting, and taken often in gillnets and other fishing gear in Sri Lanka and the Philippines. Populations in these areas with large kills have not been properly assessed. Fraser’s dolphin, Lagenodelphis hosei This tropical oceanic species is poorly known but reasonably abundant (Jefferson and Leatherwood 1994) (Figure 19). Schools of thousands are sometimes observed, and there are estimated to be more than 250,000 in the eastern tropical Pacific (Wade and Gerrodette 1993). Fraser’s dolphins have been, and probably continue to be, hunted at least opportunistically in Japan, Sri Lanka, the Philippines, Figure 18. Risso’s dolphins exhibit their typically piebald, or heavily scarred, appearance. These animals are fairly common in the Mediterranean Sea, including the Ligurian Sea Cetacean Sanctuary. Photo: Tethys Research Institute/Vittorio Fadda. Lesser Antilles, and Indonesia. There is little information on population size or abundance (outside the eastern tropical Pacific). Atlantic white-sided dolphin, Lagenorhynchus acutus This species is widespread in temperate pelagic waters across the rim of the North Atlantic (IWC 1997a; Reeves et al. 1999b). Abundance estimates off eastern North America total close to 40,000 (Palka et al. 1997; Kingsley and Reeves 1998), and there are probably at least tens of thousands in the central and eastern North Atlantic. These dolphins are hunted regularly at the Faroe Islands, where a few hundred Figure 19. Fraser’s dolphins approaching a research vessel far off New Britain in the Bismarck Sea, Papua New Guinea, March 2001. These individuals lack the bold dark stripe along the side that is so distinctive for this species, particularly on adult males. Photo: Benjamin Kahn. 40

are taken by driving in some years. Reported catches in the years from 1995 to 1998 were 157, 152, 350, and 438, respectively (Bloch and Olsen 1998, 1999; Bloch et al. 1997, 2000). Smaller numbers are taken occasionally in southern Greenland. Relatively small numbers are also killed in fishing gear throughout much of the species’ range (e.g., Palka et al. 1997; Couperus 1997). Mortality in mid-water trawls is a particular concern (Couperus 1997). No population assessment is associated with the Faroese hunting of white-sided dolphins, nor is there evidence that this aspect of the drive fishery has a long history, such as that of the pilot whale component. In the absence of any proper assessment of stock identity and abundance, it is impossible to judge whether this can be regarded as a sustainable hunt. White-beaked dolphin, Lagenorhynchus albirostris White-beaked dolphins are endemic to the northern North Atlantic, where they occur mainly on the continental shelf and in semi-enclosed waters, notably the Gulf of St. Lawrence and North Sea (Northridge et al. 1997; Kinze et al. 1997; Reeves et al. 1999a). Eastern and western populations are phenotypically distinct (Mikkelsen and Lund 1994). Estimates of abundance for a number of areas indicate that there are at least tens of thousands of these dolphins, with particularly large numbers in the Barents, Norwegian, and North seas (Øien 1996; Hammond et al. 2002). White-beaked dolphins are hunted for food in Newfoundland and Labrador, but no records are kept of numbers killed, and there has been little effort to assess stocks (but see Alling and Whitehead 1987). Peale’s dolphin, Lagenorhynchus australis This dolphin is endemic to coastal and shelf waters of the southern cone of South America, from central Chile to northern Argentina (Goodall et al. 1997a, 1997b; Brownell et al. 1999b). It also occurs around the Falkland Islands and on Burdwood Bank. In some areas it is closely associated with kelp beds. Although common within its core distribution, Peale’s dolphin is confined to near-shore waters and has a limited total range. There are no published estimates of abundance. The dolphins in Beagle Channel, the Magallanes, and southern Tierra del Fuego have been harpooned for crab bait since the 1970s. The scale of this killing was great enough to cause reduced abundance by the late 1980s. Although recent evidence suggests that the scale of this exploitation has declined and that some recovery may be occurring (Lescrauwaet and Gibbons 1994; Goodall et al. 1997b), there is an ongoing need for better information on population structure and the extent to which these dolphins may still be used as crab bait. Peale’s dolphins are subject to entanglement in gillnets set near shore, but the scale of incidental mortality is not considered large in any area of their range. There is also concern that the proliferation of salmon-culture facilities in southern Chile, especially along the indented coastline of Chiloé Island, is having a negative effect on Peale’s dolphins – similar to that reported for Pacific white-sided dolphins and killer whales in British Columbia, Canada (Morton 2000; Morton and Symonds 2002). Hourglass dolphin, Lagenorhynchus cruciger The hourglass dolphin has an oceanic circumpolar distribution in the Southern Hemisphere (IWC 1997a; Goodall 1997; Goodall et al. 1997c; Brownell and Donahue 1999). There are an estimated 144,000 dolphins south of the Antarctic Convergence in summer (Kasamatsu and Joyce 1995). The species has never been subjected to significant exploitation. A few animals are known to have died in set nets off New Zealand and in driftnets elsewhere in the South Pacific (Goodall et al. 1997c). Almost nothing is known about the ecology and behavior of hourglass dolphins. Pacific white-sided dolphin, Lagenorhynchus obliquidens This species is abundant and widely distributed across the northern rim of the North Pacific, from Baja California in the east to Japan and Taiwan in the west (IWC 1997a; Brownell et al. 1999a). Phylogeographic partitioning has been documented through mtDNA and morphometric studies (Lux et al. 1997), and differences are exhibited as latitudinal as well as longitudinal strata. For example, animals off Baja California, Mexico, differ significantly from those farther north and offshore, and animals in British Columbia and Alaska are significantly different from those in all other areas sampled thus far. Although there are probably at least hundreds of thousands of these dolphins in the offshore waters where the multinational squid driftnet fishery operated until 1992, incidental mortality in that fishery may have been high enough to cause depletion (Yatsu et al. 1994; IWC 1997a). Moderate numbers of white-sided dolphins are sometimes killed deliberately in the harpoon and drive fisheries in Japan and accidentally in gillnets and other fishing gear throughout the species’ range. There are an estimated 26,000 Pacific white-sided dolphins off the coasts of California, Oregon, and Washington (Carretta et al. 2001). A long-term study at an inshore site in British Columbia suggests an association between the local occurrence of Pacific white-sided dolphins and large-scale oceanographic events (e.g., El Niño). The same study indicates a decline in abundance of this species and other cetaceans from 1994 to 41

Dolphins, Whales and Porpoises: 2002-2010 Conservation - IUCN
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