Report of the Second Workshop on The Biology and Conservation of ...

Hong KongHung presented a review <strong>of</strong> cetacean research anda summary <strong>of</strong> <strong>the</strong> status <strong>of</strong> small cetaceans in HongKong waters (Doc. 15). Additional information onabundance <strong>of</strong> Indo-Pacific humpback dolphinswas presented by Jefferson, on fishery by-catchby Torey (Doc. 7), and on conservation measuresadopted by <strong>the</strong> Hong Kong government by Lun(Doc. 18, 21).The British dependent territory <strong>of</strong> Hong Kongbecame a Special Administrative Region(SAR) within <strong>the</strong> People’s Republic <strong>of</strong> China in1997. However, Hong Kong retains a high degree<strong>of</strong> autonomy, and <strong>the</strong> political boundary continuesto impede cooperative research.Species and distributionSince a sighting and stranding report programwas initiated by <strong>the</strong> Hong Kong governmentin 1973, 11 species <strong>of</strong> small cetaceans havebeen recorded ei<strong>the</strong>r alive or stranded in HongKong waters: Indo-Pacific humpback, commonbottlenose, Risso’s, Fraser’s, pantropical spotted,striped, spinner, long-beaked common dolphins,false killer and pygmy sperm whales, and finlessporpoises. However, most <strong>of</strong> <strong>the</strong>m are transientsor individuals that have washed ashore from<strong>of</strong>fshore waters, and only <strong>the</strong> Indo-Pacifichumpback dolphin and finless porpoise are yearroundresidents.Humpback dolphins occur in <strong>the</strong> western waters<strong>of</strong> Hong Kong (i.e. north, west and south <strong>of</strong>Lantau Island) but do not occur in <strong>the</strong> easternwaters, where finless porpoises are relativelycommon. The dolphins have a strong preferencefor <strong>the</strong> Pearl River estuarine habitat, and <strong>of</strong> <strong>the</strong>western areas, North Lantau is <strong>the</strong> major area<strong>of</strong> dolphin distribution in Hong Kong waters(Jefferson 2000). Humpback dolphins also occurimmediately west and southwest <strong>of</strong> Hong Kongwaters throughout <strong>the</strong> whole Pearl River Estuary<strong>of</strong> mainland China. In contrast, finless porpoisesare found primarily in <strong>the</strong> sou<strong>the</strong>rn and easternwaters <strong>of</strong> <strong>the</strong> territory including <strong>the</strong> survey areas <strong>of</strong>South Lantau, Lamma, Po Toi, Ninepins, Sai Kungand Mirs Bay (Jefferson et al. 2002a). In particular,<strong>the</strong> area along <strong>the</strong> southwestern coast <strong>of</strong> LammaIsland appears to be an area <strong>of</strong> concentration inwinter and spring months. Porpoises also occurin <strong>the</strong> Aizhou area, directly south <strong>of</strong> Hong Kong inChinese waters.Population statusThe most up-to-date abundance estimate <strong>of</strong>humpback dolphins in Hong Kong ranges from45 in spring to 152 in summer, based on linetransectanalysis <strong>of</strong> boat survey data (Jefferson2002b). Including <strong>the</strong> survey areas in <strong>the</strong> PearlRiver Estuary, <strong>the</strong> minimum population size fromline-transect estimates is 1,383 animals, whilemark-recapture analysis <strong>of</strong> photo-identificationdata indicates a population <strong>of</strong> at least 753 dolphins(Jefferson 2002b). Jefferson suggested thattrends in indices <strong>of</strong> abundance indicated that <strong>the</strong>population declined from 1995 to 1998 but mayhave increased since <strong>the</strong>n. O<strong>the</strong>r members <strong>of</strong> <strong>the</strong>group noted that <strong>the</strong> apparent changes could bedue to o<strong>the</strong>r factors, such as movement <strong>of</strong> dolphinsin and out <strong>of</strong> <strong>the</strong> study area, which comprisesonly part <strong>of</strong> <strong>the</strong> range <strong>of</strong> <strong>the</strong> population. Over260 individual humpback dolphins have beenidentified in Hong Kong waters and <strong>the</strong> Pearl RiverEstuary, and new individuals are still being addedto <strong>the</strong> photo-ID catalog.A preliminary peak abundance estimate for finlessporpoise in Hong Kong waters is 152 animals in<strong>the</strong> spring, while <strong>the</strong> low estimate was 55 in <strong>the</strong>autumn (Jefferson et al. 2002a). The combinedabundance estimate including all survey areas inHong Kong and <strong>the</strong> Aizhou area (directly south<strong>of</strong> Hong Kong waters) resulted in an estimate<strong>of</strong> 217 porpoises in spring and summer, which<strong>Second</strong> <strong>Workshop</strong> on <strong>the</strong> Biology and Conservation <strong>of</strong> Small Cetaceans and Dugongs <strong>of</strong> SE Asia 27