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Hong Kong's Cetaceans [electronic resource] : the biology, socioecology and behaviour of Sousa chinensis and Neophocaena phocaenoides /

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Thesis (Ph.D.)--University of Hong Kong, 1997. Includes bibliographical references (leaf 208-255). Mode of access: World Wide Web.

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... Seasonal spatial variation of dolphin occurrence in PRE has been recorded in previous studies (Parsons, 1997;Jefferson, 2000;Hung, 2008). It has been suggested that there may be an outflow of humpback dolphins during the rainy seasons towards more saline waters (Jefferson, 2000;Chen et al., 2010). ...
... Additionally, diurnal spatial variation in various sites was observed (Parsons, 1997;Hung, 2008). A recent assessment (AAHK, 2014) has indicated that the diurnal patterns of dolphin occurrence (between different times of a day and between day and night) between several sites in close proximity may be vastly different. ...
... -141 -In Hong Kong, the humpback dolphin has been observed with possible sitespecific diurnal patterns in occurrence by having 'peaks' in abundance during a day (Parsons, 1997;AAHK, 2014) or between day and night (AAHK, 2014;Pine et al., 2017). In certain survey sites in AAHK, (2014), both land-based observations and passive acoustic recordings demonstrated similar diurnal patterns in area use to this study, but with 'peak(s)' of occurrence at different time of a day between sites. ...
... Seasonal spatial variation of dolphin occurrence in PRE has been recorded in previous studies (Parsons, 1997;Jefferson, 2000;Hung, 2008). It has been suggested that there may be an outflow of humpback dolphins during the rainy seasons towards more saline waters (Jefferson, 2000;Chen et al., 2010). ...
... Additionally, diurnal spatial variation in various sites was observed (Parsons, 1997;Hung, 2008). A recent assessment (AAHK, 2014) has indicated that the diurnal patterns of dolphin occurrence (between different times of a day and between day and night) between several sites in close proximity may be vastly different. ...
... -141 -In Hong Kong, the humpback dolphin has been observed with possible sitespecific diurnal patterns in occurrence by having 'peaks' in abundance during a day (Parsons, 1997;AAHK, 2014) or between day and night (AAHK, 2014;Pine et al., 2017). In certain survey sites in AAHK, (2014), both land-based observations and passive acoustic recordings demonstrated similar diurnal patterns in area use to this study, but with 'peak(s)' of occurrence at different time of a day between sites. ...
Thesis
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The world's largest population of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary is exposed to some of the world's greatest concentration of anthropogenic threats, much of it due to the region's rapid urbanisation and industrialisation in recent decades. By assessing behavioural responses of humpback dolphins to long-term and large-scale environmental change in Hong Kong, and short-term but frequent behavioural disturbance due to unregulated dolphin-watch tourism, this study investigates humpback dolphins as a model system of a coastal delphinid in the coastal seas of the Anthropocene. Field surveys were conducted between 2011 and 2014 to identify humpback dolphins’ distribution pattern. Resource selection function was applied to model the dolphin's habitat selection process and quantify their long-term habitat preference. The results indicate that humpback dolphins display a heterogeneous pattern in habitat selectivity that is conditional to distinctive sets of key factors at different spatial scales. By using Landsat data and historic archives, and by quantifying a cumulative habitat loss over the past 40 years, this study reveals that during that time the natural shoreline providing critical ecological functions to humpback dolphins in Hong Kong has been drastically reduced. Occurrence probabilities reconstructed for the time-periods prior to major habitat alterations, and occurrence probabilities projected into future years (when all currently planned projects are to be completed) indicate a major drop of habitat use by the dolphins in areas neighbouring reclamation sites. All current Marine Protected Areas (MPAs) for humpback dolphin conservation are already affected by the ongoing environmental change and this will intensify in the future. Shore-based scan-sampling surveys were conducted between 2013 and 2014 to identify a distribution pattern of the dolphins at one of their main feeding areas in Hong Kong. With year-round sightings, the dolphins used this area selectively at different seasons and time of day. Only a small portion of the area was used as feeding location, within a narrow range of distances from shore, demonstrating a clear pattern of spatio-temporal fine-scale habitat selection that has not been accounted for in all current conservation actions in Hong Kong. Behavioural responses of humpback dolphins to small-scale dolphin-watch operations were investigated by tracking the dolphins' movement and recording fine-scale changes in the movement parameters. Analyses show that movement patterns of the dolphins, distinctive between behavioural states, were significantly altered by the presence of dolphin-watch boats. Multivariate models reveal that the disturbance by dolphin-watch operations can be seen as an external factor affecting the dolphins’ spatial decisions. Consequently, an appropriate regulatory mechanism is needed to manage the dolphin-watch tourism and minimise its impact on the target species. In summary, this study quantifies humpback dolphins’ response to large long-term and short-term chronic anthropogenic impacts, and indicates that various human activities affect the dolphins' daily behaviour and habitat selection. The conservation actions that are currently in place are ineffective in protecting humpback dolphins from man-made threats and will not be effective in preserving their habitat in the long-term. This implies serious ecological consequences and an urgent need for science-based and habitat-oriented conservation strategy.
... Crustaceans occurred among the stomach contents of 2 dolphins from northern Australian waters (Heinsohn, in litt.). Indo-Pacific humpback dolphins from southern China had a variety of estuarine fish in their stomachs, and but no squid (Jefferson 2000;Parsons 1997;Wang 1965Wang , 1995. The most common Chinese prey species were Ilisha elongata, Mugil, Coilia, Collicthys lucida, johnius, Thryssa, and Trichiurus (Jefferson 2000;Parsons 1997;Wang 1965Wang , 1995. ...
... Indo-Pacific humpback dolphins from southern China had a variety of estuarine fish in their stomachs, and but no squid (Jefferson 2000;Parsons 1997;Wang 1965Wang , 1995. The most common Chinese prey species were Ilisha elongata, Mugil, Coilia, Collicthys lucida, johnius, Thryssa, and Trichiurus (Jefferson 2000;Parsons 1997;Wang 1965Wang , 1995. ...
... The only recorded internal parasites are nematodes Anisakis alexandri from the stomach (Dailey and Brownell 1972;Hsu and Hoeppli 1933) and Halocercus pingi from the liver (Gibson and Harris 1979). In Hong Kong, lungworms (Halocercus pingi) as well as unidentified trematodes occurred in the orbits (Parsons 1997). Externally, the barnacle Syncyamus aequus occurred on animals from South Africa (Ross et al. 1994). ...
... Although the two species may appear sympatric, there is spatial and temporal segregation in the habitats they occupy. Thus, humpback dolphins prefer murky, brackish waters of the Pearl River Estuary, while finless porpoises typically are found in clear, more saline waters, often around reefs, less influenced by the freshwater input from the Pearl River (Jefferson, 2000;Parsons, 1997Parsons, , 1998b). The area north of Lantau Island has been identified as the most important habitat for Hong Kong humpback dolphins (Jefferson, 2000;Jefferson et al., 2002b; Parsons, 1998b). ...
... The area north of Lantau Island has been identified as the most important habitat for Hong Kong humpback dolphins (Jefferson, 2000;Jefferson et al., 2002b; Parsons, 1998b). There is concern that pollution, loss of habitat, and interactions with fisheries may adversely impact the populations of resident cetaceans of Hong Kong (Jefferson, 2000;Jefferson, Curry, & Kinoshita, 2002a; Minh et al., 1999;Parsons, 1997Parsons, , 1998aParsons, , 1999aParsons, , 1999bParsons, , 2004aParsons & Chan, 1998;Smith & Jefferson, 2002). ...
... Specimens for this study were collected as strandings in Hong Kong (see Jefferson, 2000;Jefferson et al., 2002a;Parsons 1997Parsons , 1998aParsons , 1999a). Entire stomachs were removed from carcasses and examined in the laboratory for presence of food matter. ...
Article
Dietary information derived from the examination of stomach contents of 29 Indo-Pacific humpback dolphins (Sousa chinensis) stranded in Hong Kong waters is presented in this study. Humpback dolphins in this area have a diet comprised nearly exclusively of fish. Prey spectrum from the 15 dolphins with contents includes a minimum of 24 species of fish, and one species of cephalopod. The croaker (Johnius sp.) was the most frequent and numerically most important prey, followed by the lionhead (Collichthys lucida) and ancho- vies (Thryssa spp.). The fish families Sciaenidae, Engraulidae, Trichiuridae, and Clupeidae accounted for over 93% of all prey consumed. Most of these prey are common in murky, brack- ish waters of estuaries and often occur in large shoals. There is some dietary overlap with fin- less porpoises (Neophocaena phocaenoides); the two species share some 13 fish species, but only anchovies figure among the top five prey for both species. In addition, finless porpoises rely more heavily on cephalopods (squids, cuttlefishes, and octopus) and may venture into deeper, clearer waters during foraging, whereas humpback dolphins seem to exploit demersal and shoaling fish of productive estuaries. The stocks of some fish species important in the diet of humpback dolphins may have been subjected to heavy exploitation by the fisheries in Hong Kong waters. Behavioral observations of dolphins feeding in association with pair trawlers suggest a somewhat different prey preference for some dolphins from the results of this study.
... The distribution of Indo-Pacific humpback dolphins, regardless of morphological type, coincides with some of the greatest densities of human population and, as such, these dolphins are exposed to a high number of anthropogenic threats such as fisheries by-catch, pollution, coastal development, and boat traffic. Because of this, there is concern about the status of humpback dolphins (e.g., IWC, 2003;Jefferson, 2000;Karczmarski, 2000;Karczmarski et al., 1998Karczmarski et al., , 2000aParsons, 1997Parsons, , 1998aParsons, , 1998cParsons, , 1998dParsons, , 1999aParsons, , 1999bParsons & Chan, 1998;Parsons et al., 1999); however, information about the biology, behavior, and ecology of this species is extremely limited and dispersed, although several studies in discrete areas (such as Hong Kong and South Africa) have added considerably to current knowledge. ...
... Contrary to this, Parsons (1998b) noted a significant relationship between the presence of chinensis-type humpback dolphins and the absence of finless porpoises in Hong Kong. In Hong Kong, humpback dolphins and finless porpoises may compete for food resources as they have a number of key prey species in common (Barros et al., 2002(Barros et al., , 2004Parsons, 1997). Barros et al. (2004) suggested that the need to reduce this competition may have led to the distributions of humpback dolphins and finless porpoises being largely separate, with the former occupying brackish estuarine waters and finless porpoises inhabiting cooler and more saline waters (Jefferson, 2000;Jefferson & Braulik, 1999;Jefferson et al., 2002;Parsons, 1998b), but when the distribution of humpback dolphins overlaps with porpoises, instead of spatially, their distribution is separated temporally (as seen in Parsons, 1998b). ...
... Hong Kong is one of the busiest ports in the world, approximately one-half million oceanic and river-going vessels travel through Hong Kong's waters every year, and 30 high-speed and hydrofoil ferries pass through the area of greatest humpback dolphin abundance daily (Parsons, 1997). In addition to changes in dolphin behavior, this boat traffic also has more direct impacts on the resident dolphin population. ...
... Nonetheless, there are indications that organochlorine contamination could disrupt the immune and reproductive systems in at least a proportion of the humpback dolphin population in Hong Kong. Parsons (1997a) estimated the highest body burden for Hong Kong's humpback dolphins was 20.6 mg.kg -1 body weight ΣPCB and 62.8 mg.kg -1 body weight ΣDDT (using contaminant data from Parsons & Chan, 1998). The LD50 level for DDT in mammals (i.e., the level of contamination at which 50% of the sample animals die as a result of a lethal dose of chemicals) is >60 mg.kg -1 body weight (Pimentel, 1971); however, as mentioned above, much of the organochlorine body burden in cetaceans is compartmentalised in the blubber and relatively, toxicologically, inert. ...
... Moreover, in this part of Hong Kong, the bioavailability of trace elements, in particular toxic cadmium, is increased as the result of lower salinities caused by the freshwater influx of the Pearl River (Morton & Blackmore, 2001). Parsons (1997aParsons ( , 1999a analysed levels of trace element contamination in whole fish caught from this area of high humpback dolphin abundance, which is adjacent to the aforementioned contaminated mud pits, and discovered that concentrations of trace metals were relatively high. There were considerable amounts of selenium (up to 109.8 µg.g -1 dry wt), cadmium, copper, mercury, and zinc (up to 56.9, 53.4, ...
... Hong Kong is known to be heavily contaminated by BTs, with high levels of TBT in coastal waters (up to 1,000 ng.L -1 ) (Lau, 1991) and concentrations up to 53,000 ngSn.g -1 noted in marine sediments (Ko et al., 1995). Hong Kong's humpback dolphins inhabit an area with not only a high volume of shipping traffic (and, hence, leaching of TBT), but also several dry-dock facilities where ships with TBT coated hulls are frequently berthed and sometimes repainted (Parsons, 1997a). In addition, there are undoubtedly numerous factories and facilities both in Hong Kong and neighbouring areas of China, that could be utilising MBT and DBT in the production and processing of commercial products. ...
Article
Indo-Pacific humpback dolphins (Sousa chinen-sis) inhabit coastal and estuarine waters close to anthropogenic sources of pollution. Detailed studies of contaminant levels on Hong Kong's population of humpback dolphins showed high levels of organochlorines, in particular DDT, and mercury contamination. These contaminant levels are high enough to impact humpback dolphin health. It is likely that several other populations of humpback dolphins are contaminated to a similar degree, and urgent research is warranted. In addition to organo-chlorine and trace element pollution, the impacts of butyltin (BT), polyaromatic hydrocarbons (PAHs), tris(4-chlorophenyl)methane (TCPMe), tris(4-chlorophenyl)methanol (TCPMeOH), and sewage pollution on humpback dolphin populations should be investigated as a matter of urgency.
... In the territorial waters of Hong Kong, Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) are the most commonly observed cetaceans (Parsons et al., 1995;Jefferson & Leatherwood, 1997;Jefferson & Braulik, 1999), however, bottlenose dolphins are rarely observed. In the period 1973-1997, 10 bottlenose dolphins stranded in this area (Parsons et al., 1995;Parsons, 1997Parsons, , 1998; two of these were live strandings (Parsons, 1998). The stomachs of four of these were examined during necropsy and their contents collected for further analyses. ...
... The highest number of these structures was assumed to represent the total number of specimens consumed of each particular prey. Back-calculation of original prey size was not possible due to the unavailability of corresponding regression equations (Parsons, 1997). Nonetheless, otolith and beak sizes are provided for future comparative studies (Table 2). ...
... Two other inshore cetaceans (Indo-Pacific humpback dolphins and finless porpoises) are the only species commonly seen in Hong Kong (Jefferson & Leatherwood, 1997;Jefferson & Braulik, 1999), and together account for over 77% of all cetacean strandings in this area (Parsons, 1998). Humpback dolphins feed almost exclusively on fish (chiefly from the croaker family Sciaenidae), and other prey associated with estuarine waters, whereas finless porpoises seem to prefer squid and other pelagic fish prey (Parsons, 1997;Barros et al., unpublished data). There are a few species shared by the bottlenose dolphins analysed in the present study and the two 'resident' species (e.g., Apogon spp., Trichiurus lepturus, Loligo spp.), but since they seem to have different distributions, they are not likely to compete significantly for similar food resources. ...
Article
The diet of bottlenose dolphins in southeast Asia is poorly known. Two forms of bottlenose dolphins occur off Hong Kong; an inshore form (aduncus- type) and an offshore form (truncatus-type), which differ in total length and other morphological fea- tures. We examined the stomach contents of four offshore bottlenose dolphins stranded between 1994 and 1997. Nine species of fish (of nine families) and three species of cephalopods (of three families) were identified as prey. These species are found in neritic and pelagic habitats, and represent both surface- dwellers as well as demersal inhabitants. Whereas some prey species may be found close to shore, others extend their distribution into deeper waters, suggesting that the dolphins may have also fed in inshore waters in the process of stranding. Although sample sizes are small, little competition with other cetacean species found around Hong Kong (Indo-Pacific humpback dolphins and finless porpoises) is suspected, as few prey species were shared by these dolphins.
... These records were updated recently by Morton et al. (1992) and Parsons et al. (1995). To date, 16 species of cetacean have been reported from Hong Kong territorial waters (Parsons, 1997). ...
... Additionally, high infant mortality is often a sign of high levels of organic contaminants in mothers, as the lactating females pass on large quantities of toxic, lipid-soluble organochlorine pollutants to their offspring via their milk (Subramanian et al., 1987;Cockcroft et al., 1989). High concentrations of these compounds have been found in the blubber and milk of Hong Kong's small cetaceans, with relatively high organochlorine burdens in finless porpoise calves: up to 54 mg XDDT kg body weight" 1 (Parsons, 1997). Therefore, organochlorine toxicity may be a factor which has led to this high proportion of neonate strandings. ...
... Hong Kong is one of the busiest ports in the world and with such high levels of human activity, in 1995, for example, 50% of S. chinensis strandings were, or were suggested to be, direct results of anthropogenic activities (Parsons, 1997). In addition, necropsied carcasses were found to be contaminated with anthropogenic pollutants, which possibly contributed to their deaths (Parsons & Chan, 1998). ...
Article
Since official records were first initiated in 1973, there have been reports of 154 small cetacean strandings in Hong Kong territorial waters. The species Neophocaena phocaenoides (finless porpoise) and Sousa chinensis (Indo-Pacific hump-backed dolphin) accounted for 77% of these strandings. There are seasonal peaks in the number of reported strandings: Sousa chinensis is more frequently reported during the summer monsoon season and Neophocaena phocaenoides is more frequent in the winter. Almost a third of all finless porpoises stranded were calves. The number of reported small cetacean strandings in Hong Kong has increased dramatically in recent years; partially due to an increasing awareness of local cetaceans and possibly due to escalating levels of human disturbance and anthropogenic pollution.
... Pollutant accumulation heavy metals shows a concerning trend (Parsons 1997, Parsons & Chan 1998, Minh et al. 1999, Jefferson 2000, Parsons 2004, Leung et al. 2005, Xing et al. 2005, Kajiwara et al. 2006, Ramu et al. 2005, Isobe et al. 2007, Gui et al. 2014a) that is likely to increase the vulnerability of the PRE dolphins ). Many of these persistent organic pollutants are thought to be endocrine disruptive, with further demographic and developmental consequences (Guillette et al. 1994, Cheek & McLachlan, 1998, Vartiainen et al. 1999, Crews et al. 2000. ...
... Hong Kong discharges over 2 billion liters of sewage into the surrounding waters daily. Parsons (1997) estimated that a humpback dolphin's minimum daily intake of sewage bacteria through ingestion of contaminated seawater could be up to 70,500 faecal coliforms. To put this in a context, a one-off ingestion rate of 200-300 coliforms is considered unacceptable for humans (Parsons 2004). ...
... The sediments and water in the PRE are heavily polluted by agricultural and industrial contaminants, such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), hexachlorocyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDT) (Guo et al., 2009;Mai et al., 2002;Wang et al., 2007). Many of these persistent organic pollutants are thought to be endocrine disruptive, with further demographic and developmental consequences (Cheek and McLachlan, 1998;Crews et al., 2000;Guillette et al., 1994;Vartiainen et al., 1999) and the potential impacts on the health of the local Indo-Pacific humpback dolphin population have long been a cause of concern Isobe et al., 2007;Jefferson, 2000;Jefferson et al., 2006;Kajiwara et al., 2006;Leung et al., 2005;Minh et al., 1999;Parsons, 1997Parsons, , 2004Parsons and Chan, 1998;Ramu et al., 2005;Wu et al., 2013;Xing et al., 2005;Yu et al., 2011a,b). Hong Kong alone discharges over 2 billion litres of sewage into the surrounding waters daily (Harrison et al., 2008;Warren-Rhodes and Koenig, 2001). ...
... Hong Kong alone discharges over 2 billion litres of sewage into the surrounding waters daily (Harrison et al., 2008;Warren-Rhodes and Koenig, 2001). Parsons (1997) estimated that a humpback dolphin's minimum daily intake of sewage bacteria through ingestion of contaminated seawater could be up to 70,500 faecal coliforms (a one-off ingestion rate of 200-300 coliforms is considered unacceptable for humans ;Parsons, 2004). The disposal of contaminated mud from various dredging and reclamation projects in PRD poses an indirect risk to dolphins via their consumption of contaminated prey (Clarke et al., 2000). ...
Article
Full-text available
In coastal waters of the Pearl River Delta (PRD) region, the Indo-Pacific humpback dolphin (Sousa chinensis) is thought to number approximately 2500 individuals. Given these figures, the putative PRD population may appear strong enough to resist demographic stochasticity and environmental pressures. However, living in close proximity to the world's busiest seaport/airport and several densely populated urban centres with major coastal infrastructural developments comes with challenges to the long-term survival of these animals. There are few other small cetacean populations that face the range and intensity of human-induced pressures as those present in the PRD and current protection measures are severely inadequate. Recent mark-recapture analyses of the animals in Hong Kong waters indicate that in the past two decades the population parameters have not been well understood, and spatial analyses show that only a very small proportion of the dolphins’ key habitats are given any form of protection. All current marine protected areas within the PRD fail to meet a minimum habitat requirement that could facilitate the population's long-term persistence. Demographic models indicate a continuous decline of 2.5% per annum, a rate at which the population is likely to drop below the demographic threshold within two generations and lose 74% of the current numbers within the lifespan of three generations. In Hong Kong, the case of humpback dolphins represents a particularly explicit example of inadequate management where a complete revision of the fundamental approach to conservation management is urgently needed.
... The basic occurrence patterns, ecology and status of members of the genus Sousa have been studied with greatest intensity off South Africa (Karczmarski, 1996) and Hong Kong (Hung, 2008;Jefferson, 2000;Parsons, 1997Parsons, , 1998aPorter, 1998), but behaviour and behavioural ecology have received less attention, except off South Africa in the 1990s (for example, Karczmarski et al., 2000b; this work and other studies are summarized in Parsons (2004a)). Especially in recent years, much attention has been paid to details of habitat use patterns in Hong Kong, with descriptions of behaviours (Hung, 2008(Hung, , 2014, social communities (Dungan et al., 2012) and sounds (Ruxton, 2002;Sims et al., 2011). ...
... Hong Kong is one of the busiest ports in the world. In the 1990s, approximately one-half million oceanic and river-going vessels were travelling through Hong Kong's waters every year (Parsons, 1997(Parsons, , 2004a. In 2013, an estimated 376,100 vessels passed through Hong Kong, which was ranked the world's fourth busiest port (Hong Kong Government, 2014). ...
Chapter
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Fewer than 200 Indo-Pacific humpback dolphins (Sousa chinensis) occur in Hong Kong waters (though these are part of a much larger population in the Pearl River Estuary), with a decrease in the past about 10 years. They have partially overlapping individual ranges (mean=100km2), and two partially overlapping communities. Seasonal occurrence is higher in June-November than December-May, approximate wet and dry monsoon seasons, respectively. Group sizes tend to average three dolphins, a decrease from the past decade. Feeding often occurs in abruptly changing water depths and off rocky natural shores. The area immediately north of Hong Kong International Airport is largely used for travelling between locations to the west, east and further north. The area around Lung Kwu Chau Island in northwest Hong Kong is a "hot spot" for foraging and socializing. The area off Fan Lau, southwest Lantau Island, is largely used for foraging. A former foraging "hot spot" was located around the Brothers Islands east of the airport, now reduced, possibly due to increases in high-speed ferries (HSFs) and other activities. Sound recordings of dolphins from bottom-mounted hydrophones suggest that northwestern Hong Kong waters are used more at night than in daytime. Sexual activity and calving occur throughout the year, with a peak in late spring to autumn (wet monsoon season). Humpback dolphins communicate acoustically with each other and probably passively listen to prey in murky waters, and anthropogenic noises may be masking communication and affecting prey location. Increasing sounds of shipping, HSFs and industrial activities are likely to alter dolphin habitat use patterns and overall behaviours beyond the present already affected status.
... The coastal toothed whale group includes finless porpoises and Chinese white dolphins, which are well known as shallow nearshore cetacean species (Parsons, 1997). They inhabit the western coast of Taiwan (Wang et al., 2004(Wang et al., , 2007Yeh, 2011). ...
... However, our d 13 C and d 15 N results show that their ecological niches are different. The finless porpoises prefer foraging in deeper, cleaner and more saline waters compared with the Chinese white dolphins which prefer foraging near shallower, murky, brackish estuaries (Parsons, 1997;Barros et al., 2004). The habitat of the Taiwanese subpopulation of Chinese white dolphins is limited to the coastal waters with a water depth of less than 17 m in western Taiwan (Wang et al., 2007;Yeh, 2011). ...
... In the mid-1990s, long-term research projects began on the ecology of populations in Xiamen (Huang & Chou, 1995;Huang & Liu, 2000aHuang et al., 2000; and Hong Kong and the Pearl River Estuary (the latter hereafter referred to as the PRE) (Hung, 2000;Hung & Jefferson, 2002, 2004Jefferson, 2000;Minh et al., 1999Minh et al., , 2000aMinh et al., , 2000bParsons, 1997Parsons, , 1998aParsons, , 1998bParsons, , 1999Parsons & Chan 1998Parsons & Jefferson, 2000;Porter, 1998;Torey, 2000). This paper summarizes information on the status of humpback dolphin populations in Chinese waters (including Taiwan). ...
... In Hong Kong waters, habitat degradation is a major threat to humpback dolphins. This comes in the form of pollution, coastal and seabed modification, water quality deterioration, prey depletion, and vessel disturbance and collisions (Parsons, 1997;Parsons & Jefferson, 2000;Porter, 1998;Torey, 2000). A major concern in Hong Kong has been the effects of coastal seabed reclamation, in particular the development of Hong Kong's new international airport, which opened in 1998 on a large, partially human-made island (see Liu & Hills, 1997). ...
Article
The status of Indo-Pacific humpback dolphins (Sousa chinensis) in Chinese waters (including Taiwan) is reviewed. Within China, humpback dolphins range from the Vietnam border north to the mouth of the Yangtze River, and there are estimated to be about eight populations in China. Little is known of stock structure, except for a preliminary conclusion that animals in Xiamen and Hong Kong represent separate populations. Abundance has been estimated only for Hong Kong and the Pearl River Estuary (about 1,500 animals) and Xiamen (80 dolphins). In the early 1960s, 36 animals were killed in Xiamen Harbor, but other direct takes appear to be rare. Incidental catches are known in Hong Kong and the Pearl River Estuary, but their impacts are not known. Only preliminary work on life history has been conducted. There appears to be a calving peak from spring to summer, and calves are about 100 cm long at birth. Scant data indicate that sexual maturity in females may occur at about 9-10 years of age, with males maturing later. Dolphins in Hong Kong and the Pearl River Estuary have indi-
... Observed group size ranged from single individuals (40.7% of sightings) to 9 animals, with a mean group size of 2.6 animals (SD = 2.12). This mean group size and range were comparable to those for observations of humpbacked dolphin in both Australia and Hong Kong (Corkeron 1990, Parsons 1997. A high proportion of encounters with solitary humpbacked dolphins has also been recorded from elsewhere in the species' range (Durham 1995, Parsons 1997. ...
... This mean group size and range were comparable to those for observations of humpbacked dolphin in both Australia and Hong Kong (Corkeron 1990, Parsons 1997. A high proportion of encounters with solitary humpbacked dolphins has also been recorded from elsewhere in the species' range (Durham 1995, Parsons 1997. ...
... As an euryhaline species, the observed population discrimination may also be linked to the migration of P. paradiseus to the river during their breeding season . The population discrimination of aquatic species is also commonly hypothesized to be influenced by a combination of genetic factors, environmental conditions, and their interplay.Previous studies in fish morphometry have revealed that the interplay between genetic and plastic responses contributes to the emergence of population differentiation, including alterations in body shape (Parsons, 1997;Pinheiro et al., 2005;Poulet et al., 2004;Robinson & Wilson, 1996;Salini et al., 2004). In previous studies, various factors have been identified that may potentially influence the population discrimination of fish, such as their dietary preferences, behavioral patterns, swimming patterns (Cullen et al., 2007;Rincón et al., 2007), hydrodynamic conditions (Imre et al., 2002), water depth (Rincón et al., 2007), and water temperature (Marcil et al., 2006). ...
Article
Full-text available
The paradise thread fish (Polynemus paradiseus) is a commercially and ecologically important euryhaline fish that primarily lives in diversified coastal and estuarine habitats. A comprehensive understanding of the divergence in body shape and discrimination in population parameters related to habitats is crucial for fisheries management and conservation endeavours. To test whether significant morphological differences exist between P. paradiseus populations inhabiting different coastal environments, a total of 366 individuals (198 male and 168 female) were collected from five distant places over three zones-Cox's Bazar (Bakkhali River) and Chattogram (Karnaphuli River) in the southeast coastal regions, Noakhali (lower Meghna River) in the southcentral zone, and Khulna (Shibsa River) and Borguna (Bishkhali River) in the southwest zones adjacent to the Bay of Bengal, Bangladesh in November 2022. The truss networking and geometric morphometric analysis (GMA) indicated variations in body shape among P. paradiseus individuals induced by sexual dimorphism. Wireframe graphs demonstrated that female individuals had wider dorsal-abdominal parts than males. Using the truss networking dataset for five coastal habitats, multivariate analyses revealed two overlapping clusters: southwest (Borguna and Khulna) populations in one cluster, while central (Noakhali) and southeast (Chattogram and Cox's Bazar) populations form separate clusters. The GMA also illustrated that the Khulna-Borguna population was located near the opposite end of the Chattogram-Cox's Bazar population axis, and the Noakhali populations were somewhat in the middle, with a high degree of overlap. Wireframe graphs displayed a significant body shape variations among populations, mainly in the snout shape, the width of the dorsal-abdominal part, the tail shape, and the head shape. The Discriminant Function Analysis revealed that there were pronounced variations in body shape between two populations located in distant regions, while there were minimum variations between two populations located close to each other. This study underscores the effectiveness of landmark-based truss networking and geometric morphometrics in discerning morphological variations across different habitats. These variations likely hold adaptive significance and are critical for informed population management and conservation strategies in the population structure of euryhaline P. paradisus.
... According to previous studies on fish morphometry, variation in morphology, like body shape changes, has been generated due to genetic and plastic responses that reinforce one other (e.g. Robinson and Wilson, 1996;Parsons, 1997). Both adaptive phenotypic changes and genetic divergence can influence the overall body shape of the fish population from a wide range of areas. ...
Article
The study was carried out to investigate the body shape variation of the Mystus gulio collected from three different salinity gradient habitats (high-salinity brackish water, low-salinity brackish water, and freshwater) and two different sources (wild and hatchery) using linear morphometric distances, landmark-based truss-networking and geometric morphometrics. A total of 436 individuals of M. gulio were collected from the high-salinity (8-15 ppt), low-salinity (2-6 ppt), and freshwater bodies (0 ppt). For wild versus hatchery sources body shape variation, 430 individuals of M. gulio were collected from various coastal rivers and hatcheries. M. gulio from different salinity gradient habitats and sources exhibited negligible sexual dimorphism. Principal component analysis (PCA) indicated that high and low salinity populations appeared to form overlapping clusters with the freshwater populations, but other multivariate analyses discriminated both populations from brackishwater habitats from the freshwater counterparts. The geometric morphometrics displayed that the body shape variation of M. gulio from salinity gradient habitats was mainly visible in the width of the dorsal-ventral part, the snout shape, the tail shape, the head region, and the eye diameter. PCA demonstrated that multivariate spaces of both the wild and captive populations overlapped each other, although many individuals of the wild population were discriminated from the culture populations. Our results showed that truss networking and geometric morphometric methods provide consistent outcomes for body shape discrimination in the M. gulio populations.
... The distribution of dolphins off Hong Kong is influenced by freshwater flowing from the Pearl River, where dolphins occur in higher densities in areas with steeper benthic slopes, often along natural island shores and rocky coastlines (Hung, 2008;Jefferson and Smith, 2016). Research concentrating on the Pearl River Estuary (PRE) population of dolphins began in the early 1990s (Parsons, 1997;Jefferson, 2000), and data show that the waters around Lantau Island (Figure 1) have historically been an important habitat for dolphins (Jefferson and Hung, 2004;Marcotte et al., 2015). In the PRE, prey availability is one of the most important factors for predicting dolphin density (Hung, 2008), and foraging opportunities may be impacted if foraging grounds of prey species are disrupted. ...
Article
Full-text available
Construction-related loss of habitat, degradation of existing habitat, noise pollution, and vessel activity are growing issues for Indo-Pacific humpback dolphins (Sousa chinensis) that occur in the shallow, near-shore, highly industrialized waters off Lantau Island, Hong Kong. We studied the occurrence of dolphins in discrete locations, fine-scale movement patterns, and dolphin behavioral activity states. Potential explanatory variables varied and included year, season, time of day, dolphin group size and behavioral activity state, proximity to construction activity, and vessel type and number. Land-based observations and theodolite tracking of dolphins and vessels were conducted from seven locations to the north of Lantau Island, Hong Kong, and marine construction activities near survey sites were identified. A total of 636 groups of dolphins were recorded, totaling 150.91 h of tracking, from 405 days of observation effort. Hurdle models were used to analyze dolphin occurrence, multivariate generalized additive models were used to analyze fine-scale movement patterns, and log-likelihood ratio and binomial z score post hoc tests were used to analyze behavioral activity states. Dolphin occurrence was lower in historically important areas near long-term, low-intensity construction activity, and dolphin swimming speed was higher in response to vessel presence. Overall, foraging and traveling were the most frequently observed behavioral activity states and resting behavior was observed off only one location that was not in proximity to construction activities. Temporal overlap in adjacent marine construction areas may displace animals for extended periods and nearby ecologically similar habitats should be identified and designated as marine protected areas to mitigate effects of such disturbance.
... Within Southeast Asia, one species occurs, S. chinensis, which consists of a number of suspected populations. Apart from the population which dwells within the Pearl River Estuary (Jefferson and Leatherwood, 1997;Parsons, 1997;Porter et al., 1997;Porter, 1998;Jefferson, 2000;Porter, 2002), until very recently, little has been known of distribution within the region (Perrin et al, 1996;Wang and Han, 2006). There is considerable concern over the survival of this and other cetacean species within Southeast Asia due to the accumulative impacts from fisheries activities, heavy ship traffic, coastal development and pollution. ...
Conference Paper
Full-text available
During the period June 2004 - January 2006, a research team from the Qinzhou Bay Chinese White Dolphins Research Center of Peking University, the Peoples Republic of China, conducted systematic and opportunistic boat surveys of Sanniang Bay, Guangxi Province, in which Indo-Pacific humpback dolphins Sousa chinensis were regularly seen. Ninety eight dolphins were photographically identified. The dolphins appear to inhabit a small, shallow area of core habitat within the greater Sanniang Bay area. They do not appear to travel up the two rivers which are located to each side of the bay. Of the five populations known from the coastal area of China, the one that resides in Sanniang Bay is determined as having the least impact from anthropogenic activities. The area itself has been designated as a nature tourism location and considerable effort and money has been spent on developing appropriate tourist facilities. The dolphin watching industry in the area is strictly monitored and controlled by one local authority. The largest estuary adjacent to Sanniang Bay has been allocated for industrial development and a paper pulp mill will be established there. Considering the investment already made in the nature tourism industry, the natural beauty of the bay and the surrounding area and the likelihood that this is the only population of Indo-Pacific humpback dolphins which remain in uncompromised and relatively pristine habitat in all of China, it is urged that all effort be made to maintain the natural integrity of the bay. It is recommended that all development and operational aspects of the paper pulp be thoroughly scrutinized and all efforts made to minimize impact upon the environment and that all current and future industries and activities in this area must not detrimentally impact the dolphin population or compromise the integrity of the bay ecosystem.
... The Indian Ocean humpback dolphins are well known to occur along the Indian coast and its adjacent estuaries, but the study on their interaction with fishing nets and aggregation around the artisanal nets are limited (Suttaria and Jefferson, 2004). The dolphins try to get food from the fishing nets of artisanal fishers because of its easy feeding strategies which is an adaptation by dolphins to save energy while foraging (Jefferson, 2000;Parsons, 1997;and Parsons, 1998). While doing so the dolphins get entangled into the fishing net or ...
Article
Full-text available
Karanja estuary, an important estuarine ecosystem located adjoining to the Jawaharlal Nehru Port (largest container handling Seaport in India), Raigad district of Maharashtra. The North West coast of India is famous for the dol nets fishery. Dol nets (a kind of bag net) are operated in coastal seas having strong tidal currents and amplitude with its mouth opening always facing towards the direction of the tide. The present study was undertaken from September 2016 to May 2017 in Karanja estuary to record the Indian Ocean humpback dolphin pods and their interaction with dol nets and to understand the effect of anthropogenic activities on their population. The dolphins were identified to be as Indian Ocean humpback dolphin, Sousa plumbea by using surface photo identification (photo-ID) techniques that rely on the natural marks on their dorsal fins, flukes and spot patterns. The food availability was found to be a significant reason for the interaction of dolphin with dol nets. The survey was conducted among the fisher folks to analyse the various threats associated with the dolphin pod survival. The stranding details of the dolphins around the study regions, recorded in past years, showed that this species is facing the pressure for its existence. The IUCN lists this species as endangered (EN) in the Red List of threatened species hence the immediate action is needed to protect this species before it becomes extinct from the estuarine habitat.
... Island (PADS 1989). Early studies investigated the distribution, behaviour, diet, group dynamics, and pollutant impacts on humpback dolphins in Hong Kong (Parsons 1997;Porter 1998;Jefferson 2000 Gui et al., 2014Gui et al., , 2017Zheng et al. 2016). However, population parameters and structure, social dynamics, range use patterns and habitat choice in relation to specific behaviours, and how social and spatial patterns change in response to human activities remains poorly understood; and much of the previous work has suffered from various methodological deficiencies (see Wilson et al. 2008 for a detailed critique). ...
... The distribution of dolphins off Hong Kong is influenced by freshwater flowing from the Pearl River, where dolphins occur in higher densities in areas with steeper benthic slopes, often along natural island shores and rocky coastlines (Hung, 2008;Jefferson and Smith, 2016). Research concentrating on the Pearl River Estuary (PRE) population of dolphins began in the early 1990's (Jefferson, 2000;Parsons, 1997), and data show that the waters around Lantau Island (Figure III-1) have historically been an important habitat for dolphins Marcotte et al., 2015). In the PRE, prey availability is one of the most important factors for predicting dolphin density (Hung, 2008). ...
Thesis
This dissertation contributes to our understanding of anthropogenic effects on wildlife, a central question in the growing field of conservation behavior. I present three case studies of coastal delphinid species in diverse ecosystems with varied human pressures. I examine how 1) common bottlenose dolphins (Tursiops truncatus) in a narrow congested waterway respond to heavy vessel traffic, 2) Indo-Pacific humpback dolphins (Sousa chinensis) respond to chronic maritime construction and associated vessel activity, and 3) dusky dolphins (Lagenorhynchus obscurus) use distinct patches within a bay that supports shellfish aquaculture. In each study, group focal follows were conducted using non-invasive shore-based theodolite tracking. Data collection included behavioral states, movement patterns and habitat-use patterns. Metrics to evaluate alterations in movement patterns included swimming speed, reorientation rate, and linearity. Data to evaluate alterations in habitat-use included behavioral activity states and track duration among habitat patches. Multivariate generalized additive models identified significant explanatory variables. Dolphin movement and habitat-use patterns were good indicators of response to human activity across diverse species and ecosystems. Bottlenose dolphins avoided tour boats and were attracted to commercial trawlers that may facilitate prey accessibility. Current voluntary dolphin-viewing recommendations do not protect dolphins from behavioral harassment, but dolphins did not abandon the area, which may reflect a lack of ecologically similar habitat nearby. Humpback dolphins avoided areas near chronic construction activity during the day, but some returned at night when human activity decreased. Dusky dolphins used defined patches within the bay in different ways. Mid-bay and nearshore patches reflect areas that may yield greater benefits relative to prey ball herding opportunities, whereas patches near mussel farms reflect areas that may yield greater benefits relative to non-prey ball foraging opportunities. Flexibility in foraging tactics occurred across study sites and species, and allows dolphins to adjust to fluctuating environments with ephemeral and patchily distributed prey. Behaviors are likely influenced by human activity, prey characteristics, and accessibility to alternate habitats that support prey. Integration of data on prey characteristics (e.g., fish species, abundance, and distribution) in future research will enhance our understanding of factors influencing dolphin behavior in these dynamic systems.
... When the construction of the present Hong Kong International Airport on Chek Lap Kok Island began in 1993, there were concerns that local humpback dolphin habitat would be degraded and destroyed, and that the dolphins would be seriously threatened (Leatherwood and Jefferson, 1997;Liu and Hills, 1997). To understand the potential impacts of this project on local marine mammals, the Hong Kong Special Administrative Region (SAR) Government funded several long-term studies on the status and biology of the two resident cetaceans, humpback dolphins and finless porpoises, within Hong Kong's territories (Parsons, 1997;Porter, 1998;Jefferson, 2000a;Jefferson, 2000b;Jefferson, 2007;Jefferson et al., 2002;Jefferson et al., 2006;Jefferson and Hung, 2004;Jefferson and Hung, 2007), and these studies are still ongoing (Hung, 2013). ...
Thesis
Full-text available
Marine mammals with near-shore distributions are susceptible to human-related recreational and commercial disturbances, particularly near densely populated and industrialized coastal areas. A population of over 2,500 Chinese humpback dolphins (Sousa chinensis chinensis) occupies the Pearl River Estuary in southern China. A part of this population uses Hong Kong’s waters off of Lantau Island, where they are subjected to a number of anthropogenic threats, including vessel disturbance, fisheries interactions, and boat-based tourism. Previous research has shown that the abundance of this subspecies in Hong Kong’s waters has declined about 60% since 2003. Using a combination of acoustic recordings, dolphin distribution and abundance data, and vessel traffic information I found that: 1) Four types of vessels common to the waters on Hong Kong generate noise that is audible to Sousa chinensis chinensis; 2) The spatial distribution of underwater noise in Hong Kong’s waters does not significantly vary among the six sites sampled; 3) High-speed ferry traffic and passenger volume has increased dramatically during the study period; 4) There has been a significant decline in dolphin density in areas within and near vessel traffic; and 5) Dolphins are most at risk of vessel collisions and being exposed to vessel noise near Fan Lau and within the Urmston Road waterway just northeast of the Sha Chau and Lung Kwu Chau Marine Park . These results can inform future acoustic studies on this species and guide conservation and management efforts in Hong Kong.
... In order to assess the trophic transfer risk from the prey items, TE concentrations of the potential prey species in the PRE were sampled and analyzed in this study. According to Parsons (1997), Barros et al. (2002), and our preliminary examination of the stomach contents in stranded individuals, N. phocaenoides in the PRE tends to feed on estuarine prey items, including the estuarine fish, crustaceans and cephalopods. Based on this information, 11 prey species in a similar size as the length of the preys appeared in the digestion guts of animals were collected by trawling from the key habitats of N. phocaenoides from January 2011 to June 2012. ...
... Island (PADS 1989). Early studies investigated the distribution, behaviour, diet, group dynamics, and pollutant impacts on humpback dolphins in Hong Kong (Parsons 1997;Porter 1998;Jefferson 2000 Gui et al., 2014Gui et al., , 2017Zheng et al. 2016). However, population parameters and structure, social dynamics, range use patterns and habitat choice in relation to specific behaviours, and how social and spatial patterns change in response to human activities remains poorly understood; and much of the previous work has suffered from various methodological deficiencies (see Wilson et al. 2008 for a detailed critique). ...
... Four habitat types ( Figure 5.3) were defined for the ECOSPACE simulations, viz., 'non-reef', 'natural reefs' (which includes coral and rocky reefs), 'marine mammal' and 'artificial reefs' habitats. (2000), while the marine mammal habitat distribution was based on Parsons (1997). AR distribution was based on information from AFCD, as summarized in Habitat preference of each functional group (Table 5.2) for reef, non-reefs or marine mammal habitat were assigned as follows: corals and RA groups were assigned to reef habitat only, LBS and NRA groups were assigned to both non-reefs and marine mammal habitats, the marine mammal group was assigned to reefs and mammal habitats. ...
... Four habitat types ( Figure 5.3) were defined for the ECOSPACE simulations, viz., 'non-reef', 'natural reefs' (which includes coral and rocky reefs), 'marine mammal' and 'artificial reefs' habitats. (2000), while the marine mammal habitat distribution was based on Parsons (1997). AR distribution was based on information from AFCD, as summarized in Habitat preference of each functional group (Table 5.2) for reef, non-reefs or marine mammal habitat were assigned as follows: corals and RA groups were assigned to reef habitat only, LBS and NRA groups were assigned to both non-reefs and marine mammal habitats, the marine mammal group was assigned to reefs and mammal habitats. ...
Technical Report
Full-text available
The Hong Kong Agriculture, Fisheries and Conservation Department (AFCD) has initiated a $HK100 million Artificial Reef and Fishery Protected Area (AR/FPA) programme (Figure 1.1). The proposal builds on earlier initiatives to establish ARs in Hoi Ha Wan and Yat Chau Tong Marine Parks. The objective is to rebuild fish stocks by compensating for habitat loss and reducing fishing pressure. An extensive consultation process conducted by ERM-HK Ltd., under contract to AFCD, identified five priority deployment areas. The University of British Columbia Fisheries Centre (UBC-FC) advised on Phase I consultations with fishing communities and conducted extensive ecosystem (ECOPATH and ECOSIM) and bio-economic modelling to determine the effectiveness of different sizes of FPAs around AR complexes. The earlier results indicated that a potential for substantial gains in the value of Hong Kong fisheries resources. This study is the first application of spatial (ECOSPACE) modelling to Hong Kong and adjacent PRC inshore waters and evaluates the effectiveness of different FPA configurations in the Tap Mun/Tolo Harbour and Outer Port Shelter FPAs shown below. The overall modelling also evaluates the benefits of recent AR/FPA initiatives in banning trawling at FPAs, Marine Parks and at the newly established Marine Exclusion Zone at Chek Lap Kok. Lastly, the study assesses the implication of a 2-month trawl moratorium in adjacent PRC inshore waters. (http://www.fisheries.ubc.ca/node/3814)
... Within Southeast Asia, one species occurs, S. chinensis, which consists of a number of suspected populations. Apart from the population which dwells within the Pearl River Estuary (Jefferson and Leatherwood, 1997; Parsons, 1997; Porter et al., 1997; Porter, 1998; Jefferson, 2000; Porter, 2002), until very recently, little has been known of distribution within the region (Perrin et al, 1996; Wang and Han, 2006). There is considerable concern over the survival of this and other cetacean species within Southeast Asia due to the accumulative impacts from fisheries activities, heavy ship traffic, coastal development and pollution. ...
Conference Paper
Full-text available
During the period June 2004 - January 2006, a research team from the Qinzhou Bay Chinese White Dolphins Research Center of Peking University, the Peoples Republic of China, conducted systematic and opportunistic boat surveys of Sanniang Bay, Guangxi Province, in which Indo-Pacific humpback dolphins Sousa chinensis were regularly seen. Ninety eight dolphins were photographically identified. The dolphins appear to inhabit a small, shallow area of core habitat within the greater Sanniang Bay area. They do not appear to travel up the two rivers which are located to each side of the bay. Of the five populations known from the coastal area of China, the one that resides in Sanniang Bay is determined as having the least impact from anthropogenic activities. The area itself has been designated as a nature tourism location and considerable effort and money has been spent on developing appropriate tourist facilities. The dolphin watching industry in the area is strictly monitored and controlled by one local authority. The largest estuary adjacent to Sanniang Bay has been allocated for industrial development and a paper pulp mill will be established there. Considering the investment already made in the nature tourism industry, the natural beauty of the bay and the surrounding area and the likelihood that this is the only population of Indo-Pacific humpback dolphins which remain in uncompromised and relatively pristine habitat in all of China, it is urged that all effort be made to maintain the natural integrity of the bay. It is recommended that all development and operational aspects of the paper pulp be thoroughly scrutinized and all efforts made to minimize impact upon the environment and that all current and future industries and activities in this area must not detrimentally impact the dolphin population or compromise the integrity of the bay ecosystem.
Article
Full-text available
Order Cetacea, suborder Odontoceti, family Delphinidae. The genus Sousa has traditionally been united with Steno and Sotalia in the subfamily Steninae (sometimes elevated to family level), based on morphologic similarities (Barnes et al. 1985). However, cytochrome b sequences do not support this grouping among Delphinidae (LeDuc et al. 1999) and instead suggest a relationship of Sousa with Delphinus, Lagenodelphis, Stenella, and Tursiops. Ross et al. (1995) proposed only 1 species under the name Sousa chinensis, with possibly 3 or more subspecies, whereas Rice (1998) listed 3 species, S. teuszii, S. plumbea, and S. chinensis (Atlantic, Indian, and Pacific ocean humpback dolphins, respectively). Most recent authors recognize only 2 species: S. teuszii (Atlantic humpback dolphin) and S. chinensis (Indo-Pacific humpback dolphin).
Article
Since the early 1990s, there has been an active program in Hong Kong to manage and protect local populations of small cetaceans from the effects of massive development in the area. This paper reviews the progress that has been made. Only two species regularly occur there: the Indo-Pacific humpback dolphin and the finless porpoise. Because most development has occurred in the western waters of Hong Kong, where generally only the humpback dolphin occurs, most of the work has been conducted on that species. Development of large infrastructure projects (such as airports, bridges, expressways, power plants, fuel facilities, and container ports) in Hong Kong often results in land reclamation, dredging and dumping of spoils, pipe and cable laying, percussive and bored piling work, underwater blasting, large increases in vessel traffic, and other impacts. Several mitigation measures have been used with varying levels of success, including bubble curtains/jackets, exclusion zones, ramping up of piling hammers, acoustic decoupling of noisy equipment, vessel speed limits, no-dumping policies, and silt curtains. Baseline, construction-phase, and operational-phase cetacean monitoring is often conducted to evaluate the success of conservation measures put into place. The Environmental Impact Assessment process in Hong Kong has involved cetaceans to a degree perhaps higher than anywhere else in the world, and much can be learned from studying the successes and failures of this situation.
Article
The territorial waters of Hong Kong are highly contaminated with anthropogenic pollutants, including trace metals. Hong Kong's population of Indo-Pacific hump-backed dolphins (Sousa chinensis) inhabits an area where a high volume of sewage waste discharge and the close proximity of contaminated mud pits mean a considerable potential for trace metal contamination. Trace metal concentrations in the muscle tissue of fish caught from areas of high dolphin abundance are notable. However, in order to gauge the amount of trace metal consumed by dolphins, whole fish must be analysed. Whole fish from areas of high dolphin abundance have considerably higher trace metal loads than muscle tissue alone. Considering the consumption of prey items by dolphins, a daily intake of trace metals was estimated as As, 410-518; Cd, 34-44; Co, 4-5; Cr, 40-50; Cu, 44-56; Hg, 51-66; Mo, 22-27; Ni, 19-24; Pb, 320-403; Se, 99-125 and Zn, 388-490 (microgram kg-1 body wt. per day). Concentrations of arsenic, chromium, lead, molybdenum and nickel in dolphin tissues were an order of magnitude lower than in prey items, suggesting these elements may be excreted by this species. Mercury concentrations in dolphin tissues were, however, an order of magnitude higher than in prey items and could be considered potentially health threatening (max: 906 micrograms kg-1 dry wt.). Hong Kong's Indo-Pacific hump-backed dolphin population has a high dietary intake of trace metals which may, especially in the case of mercury, be a cause for concern.
Article
Stranded cetaceans reported from the territorial waters of Hong Kong during the period May 1993 to March 1998 were examined to establish factors that may have contributed to their death. During the current study, 28 Indo-Pacific hump-backed dolphins (Sousa chinensis), 32 finless porpoises (Neophocaena phocaenoides), and four bottlenose dolphins (Tursiops truncatus) were necropsied. Bacteria (15 species) were isolated from nine animals. Of these bacteria, 47% were of possible fecal origin reflecting the high level of sewage contamination in Hong Kong's waters. One finless porpoise displayed wounds caused by a shark attack, and two female finless porpoises presented prolapsed uteri. At least 10 finless porpoises showed evidence of moderate to heavy lungworm infections (Halocercus pingi), and this appears to have been a factor contributing to death in at least six animals. Evidence suggesting blunt traumatic injury (probably caused by boat collisions) was found in six cetaceans (three finless porpoises and three hump-backed dolphins). Signs of fishery-related mortality were detected in at least nine animals (six hump-backed dolphins, two finless porpoises, and one bottlenose dolphin). Of these two human-caused mortality types, pre-existing disease or bacterial infection were detected in 29% of cases. Results indicate that human factors may have played a significant role in the death of at least 15 animals (32% of hump-backed dolphins, 15% of finless porpoises, and 25% of bottlenose dolphins).
Article
Between 1993 and 1998, 28 Indo-Pacific hump-backed dolphins (Sousa chinensis) and 32 finless porpoises (Neophocaena phocoenoides) stranded in Hong Kong territorial waters were examined postmortem for parasites. The nematode Halocercus pingi was discovered in the lungs of one hump-backed dolphin and in 10 finless porpoises, typically within abscesses or granulomata, and they were frequently accompanied by a catarrhal exudate and lesions characteristic of pneumonia. Seven of the 10 finless porpoises were calves with substantial lungworm infections, and three were neonates with visible fetal folds and umbilical remnants, suggesting that H pingi is transferred to the neonate before birth or during lactation. Electron micrographs of H pingi should allow the nematode to be identified by other researchers. An ectoparasitic stalked barnacle (Xenobalanus globicipitis) was recovered from a finless porpoise, the first time that this species of barnacle has been recorded in Hong Kong's territorial waters.
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