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

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


Brahmaputra-Megna, and Karnaphuli-Sangu river systems, the Platanista river dolphins have declined in abundance and in the extent of their range. These cetaceans must compete with humans for shrinking water resources. Largescale engineering projects that give people hope for economic development and relief from flood and famine pose dire threats to river cetaceans and other aquatic wildlife. Freshwater populations of Irrawaddy dolphins are also threatened by development projects in the Mekong river system of Vietnam, Cambodia, and Laos, and probably also in the Ayeyarwady (formerly Irrawaddy) River of Myanmar and the Mahakam River of Indonesia. Freshwater cetaceans are also threatened by the enormous pollutant loads carried in Asian waterways (Dudgeon 1992), and by destructive fishing activities, which result in high mortality from bycatch and reduced availability of prey. These animals are perhaps more vulnerable to these threats, in comparison to marine cetaceans, because their habitat requirements often place them in areas where human activities are most intense (Smith and Smith 1998). Little is known about the status of most coastal cetacean populations in Asia. In many areas, even the most basic information, such as what species are present, is lacking. Particular problems relate to distinct populations (e.g., dwarf spinner dolphins) and poorly documented species (e.g., pygmy Bryde’s whale). Recent projects in Vietnam (Smith et al. 1997b; Andersen and Kinze 2000), Thailand (Andersen and Kinze 1999), Myanmar (Smith et al. 1997a), Indonesia (Rudolph et al. 1997), and the Philippines and Malaysia (Dolar et al. 1997) have revealed diverse inshore cetacean faunas, but also serious threats, including fishery bycatch, deliberate killing, and possibly reduced prey due to overfishing. Throughout the continent, there is an urgent need for better information on the status of species and populations, and for the development of local expertise to help devise, advocate, and implement conservation programs (Perrin et al. 1996). Information is particularly lacking for western Asia (e.g., Iran and the Arabian peninsula), and the absence of projects for this region represents a significant gap that should be filled in subsequent action plans. Projects 1. Monitor and evaluate ongoing threats to the Irrawaddy dolphins in the Mahakam River of Indonesia The Critically Endangered Irrawaddy dolphins in the Mahakam River of East Kalimantan range in the mainstem from about 180km to 600km upstream of the mouth, seasonally entering several tributary rivers and lakes (Kreb 2002). The total population was estimated to number fewer than 50 individuals based upon eight surveys of their entire range conducted in 1999 and 2000. The dolphins were found primarily in deep pools located near confluences and meanders, which are also primary fishing grounds and subject to intensive motorized vessel traffic. Between 1997 and 1999, 16 deaths were recorded (ten from gillnet entanglement, three probably from vessel strikes, and three deliberate)(D. Kreb, pers. comm.). From 1997 to 1998, at least seven dolphins were also illegally live-captured from the river and taken to oceanaria, and plans exist to capture more animals for a new oceanarium to be built in Tenggarong (D. Kreb, pers. comm.). Intensive fishing with gillnets, electricity, and poison, and the accidental introduction of an exotic piscivorous fish, locally known as ikan toman, may have depleted the dolphins’ prey (D. Kreb, pers. comm.). The high density of gillnets used in Semayang and Melintang lakes causes physical obstruction to dolphin movements, thereby reducing available habitat. This problem, together with sedimentation caused by devegetation of the surrounding shorelines, has probably resulted in the elimination of these lakes as primary habitat as reported by Tas’an and Leatherwood (1984). Leaks from dams in the upper reaches that retain mining wastes, including mercury and cyanide, occurred in 1997 and resulted in a massive fish kill (D. Kreb, pers. comm.). An ongoing program, started in 1997 and conducted jointly by the University of Amsterdam and the East Kalimantan Nature Conservation Authority (Balai Konservasi Sumber Daya Alam Kal), has involved extensive monitoring of the Mahakam dolphins. This program should be continued and expanded to include toxicological and genetic analyses of tissues obtained from stranded or incidentally killed dolphins, investigations of factors that continue to degrade dolphin habitat, and further efforts to monitor abundance. The involvement of local scientists is vital. Because of this population’s Critically Endangered status, every effort should be made to prevent any further catches (including live-capture) and improve the quality of the riverine environment (Chapter 6). 2. Investigate the status of cetaceans in the Indonesian archipelago Indonesia is a huge country, with tens of thousands of islands and extensive, varied marine habitats (Figure 25). Indonesia’s marine waters harbor a greater variety of species than any area of comparable size in the world (Gray 1997). Species of particular conservation interest in Indonesian near-shore waters include the Irrawaddy dolphin, Indo-Pacific humpbacked dolphin, Indo-Pacific bottlenose dolphin, finless porpoise, and small-type (pygmy) Bryde’s whale. Relatively little is known, however, about the abundance and distribution of cetaceans in the region (Rudolph et al. 1997). Research has been limited primarily to the two whaling villages of Lamalera and Lamakera on the islands of Lembata and Solor, respectively (Barnes 1991, 1996); the small freshwater population of Irrawaddy dolphins in the Mahakam River (Project 1, above); waters near Manado, at the northern tip of Sulawesi 56

Figure 25. A sperm whale lifts its flukes as it dives near Manado Tua, a volcanic island within Bunaken Marine Park, northern Sulawesi, Indonesia, April 1999. This observation of a deepwater animal so close to a shoreline illustrates the extreme habitat gradients that typify the eastern parts of Southeast Asia, New Guinea, and the Solomon Islands. Photo: Benjamin Kahn. (P. Rudolph, pers. comm.); and Komodo National Park (Kahn 2000). Hunting is largely unregulated throughout most of Indonesia, and environmental degradation proceeds unchecked. Political instability exacerbates such problems. This project is intended to provide better documentation of Indonesia’s cetacean fauna and a better understanding of the conservation issues affecting these species (cf. Rudolph et al. 1997). Although the ultimate goal should be to contribute to the development of a national conservation plan, it will be necessary to begin with visits to sites suspected of supporting high cetacean diversity or abundance. Information should be obtained initially through interviews with local people, beach and fish-market surveys, and opportunistic vessel surveys (Aragones et al. 1997). dolphins taken annually in San Francisco (Perrin et al. 1996) and smaller numbers taken for bait in shark and chambered nautilus (Nautilus pompilius) fisheries in Palawan (Dolar et al. 1994). Although the hunting of small cetaceans is believed to have declined as a result of protective legislation, monitoring has become more difficult because fishermen are secretive in disposing of their catches (Dolar et al. 1994). Following the recommendations of Perrin et al. (1996), cetacean surveys were conducted in the eastern (Dolar and Perrin 1996) and southern (Dolar et al. 1997) Sulu Sea, and in Malampaya Sound, Palawan (Dolar et al. 2002). This latter survey focused primarily on a small isolated population of Irrawaddy dolphins. A more intensive investigation of Malampaya Sound was conducted by WWF-Philippines in 2001. The efforts of scientists and NGOs in the Philippines should be continued and strengthened, with the continuing emphasis on capacity-building. Assessment of illegal hunting and of incidental catches in tuna purse seine and drift gillnet fisheries remains a high priority. Intensive surveys should be conducted to assess cetacean abundance and threats in biodiversity hotspots that already receive conservation attention, such as the Tubbataha National Park and World Heritage Site and adjacent Cagayan Islands. Valuable cetacean research in these areas can often be incorporated with other conservation activities, at little extra cost. More extensive surveys should involve cooperation with neighboring countries, e.g., the joint Philippines/ Malaysia survey in the Sulu Sea (Dolar et al. 1997) and a planned Philippines/Indonesia survey in the Sulawesi Sea (W.F. Perrin, pers.comm.). Both were organized under the auspices of the Convention on Migratory Species. The Irrawaddy dolphin population in Malampaya Sound presents a particular conservation challenge due to its small size and apparent isolation (Chapter 6). Long-term 3. Assess the status of cetacean populations and levels of incidental mortality in the Philippines There has been a tremendous increase in knowledge about cetaceans in Philippine waters in recent years (Figure 26). Much of the motivation for conducting research in this region came from concern about reported kills of small cetaceans in directed fisheries and as bycatch. At fish landing sites along the south-western end of Negros Island, Dolar (1994) examined the carcasses of 20 Fraser’s, 18 spinner, and 12 Risso’s dolphins caught by a fleet of around 15 drift gillnetters over a 16-day period. Based on information from fishermen, the same author estimated that about 2000 dolphins, primarily spinner, pantropical spotted, and Fraser’s, were being killed each year by a fleet of five tuna purse seiners using fish-aggregating devices. Directed fisheries for small cetaceans were also reported, with as many as 200–300 Figure 26. A melon-headed whale breaching in the Philippines, July 1995. This species has a circumtropical distribution and often occurs in schools of 100 or more individuals. Its biology and status are not well known. Photo: Thomas A. Jefferson. 57

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