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

can be viewed as <strong>the</strong> minimum population size(Jefferson et al. 2002a).From 1995 to 2001, <strong>the</strong> stranding rate <strong>of</strong>humpback dolphins was fairly consistent, with6 to 11 strandings per year. There were 8 to 15strandings <strong>of</strong> finless porpoises per year during <strong>the</strong>same period.Habitat statusIn Hong Kong waters, dolphins and porpoises areunder great pressure from human activities. Themarine habitat is deteriorating due to coastaldevelopment, pollution from sewage and watertreatment plants, dredging for marine fill andshipping, and intensive fishing. The waters wherehumpback dolphins commonly occur have beenaffected by numerous human activities, including<strong>the</strong> construction <strong>of</strong> a new airport at Chek LapKok, which destroyed a large amount <strong>of</strong> coastalhabitat. In association with <strong>the</strong> new airportdevelopment, underwater contaminated-mud pitswere located near <strong>the</strong> airport for dumping <strong>of</strong> toxicwastes. In <strong>the</strong> same area, <strong>the</strong>re are three majoroutfalls for discharging untreated sewage. Therecent reclamation project at Penny’s Bay, <strong>the</strong>future Disneyland site, has resulted in fur<strong>the</strong>rhabitat loss for <strong>the</strong> dolphins and porpoises. Seabeddredging and disposal related to <strong>the</strong>se and o<strong>the</strong>rcoastal developments could worsen <strong>the</strong> problem<strong>of</strong> water pollution, which in turn may threatendolphins and porpoises.Sewage from <strong>the</strong> domestic and industrial sectorsand insecticides from farms drain into <strong>the</strong> sea withlittle or no treatment. High levels <strong>of</strong> environmentalcontaminants including heavy metals (e.g. mercuryand cadmium), organochlorines (e.g. DDTs, PCBsand HCHs) and organotins (TBTs), have beenfound in <strong>the</strong> blubber, liver and kidney <strong>of</strong> strandeddolphins and porpoises from Hong Kong (Parsonsand Chan 1998; Minh et al. 1999; Parsons 1999;Jefferson 2000; Jefferson et al. 2002b). Although<strong>the</strong> health implications <strong>of</strong> <strong>the</strong>se environmentalcontaminants are not fully understood, <strong>the</strong> highlevels <strong>of</strong> pollutants could pose serious healthproblems for local cetaceans, particularly incombination with o<strong>the</strong>r anthropogenic threatfactors (Jefferson 2000; Parsons and Jefferson2000).Vessel collision is ano<strong>the</strong>r significant cause <strong>of</strong>death for local cetaceans. Hong Kong is one <strong>of</strong> <strong>the</strong>world’s busiest ports. The Urmston Road shippingchannel is situated in <strong>the</strong> area <strong>of</strong> highest density<strong>of</strong> humpback dolphins, and a major fast-ferry lanebetween Hong Kong and Macao also runs throughimportant finless porpoise habitat just south <strong>of</strong>Lantau Island. Dolphins and porpoises may behit by high-speed vessels and become seriouslyinjured or killed (Jefferson 2000; Parsons andJefferson 2000; Jefferson et al. 2002b). A fewidentified individual dolphins have permanentinjury marks on <strong>the</strong>ir bodies and fins caused bypropellers, and several stranded dolphins andporpoises have borne wounds consistent withblunt traumatic injury, probably caused by boatcollisions.Overfishing in Hong Kong and <strong>the</strong> adjacent watersmay lead to depletion <strong>of</strong> food resources forlocal cetaceans, although <strong>the</strong>re is no evidence <strong>of</strong>this at present. In addition, underwater noisesgenerated by marine traffic and developmentprojects such as piling work can affect <strong>the</strong> ability<strong>of</strong> dolphins and porpoises to locate <strong>the</strong>ir foodand communicate. Sometimes it can even causeinjury or death.Directed catchesDirect killing or deliberate capture <strong>of</strong> humpbackdolphins and finless porpoises have notbeen reported in Hong Kong and nearbywaters. Fishermen in Hong Kong generally regarddolphins and porpoises as sacred creatures <strong>of</strong> <strong>the</strong>sea and do not willfully harm or disturb <strong>the</strong>m.28 CMS Technical Series Publication Nº 9 - 2005