[show abstract][hide abstract] ABSTRACT: Biological and fisheries data were analysed to assess the impact of fisheries mortality on a Critically Endangered subpopulation of <100 humpback dolphins Sousa chinensis in the eastern Taiwan Strait (ETS). Substantial interactions between ETS S. chinensis (hereafter Sousa) and fishing gear are known to cause dolphin mortality. In 2009, a total of 6318 motorised fishing vessels were operating from ports within Sousa habitats. An average of 32 fishing craft per kilo- metre was observed along a 200 km stretch of Sousa habitat. Based on a photo-identification cat- alogue, >30% of the ETS Sousa subpopulation exhibited injuries caused by fishing gear. Three individuals were photographed with fishing gear attached to their bodies, and 1 dolphin was found dead with fresh injuries caused by fishing gear. To ensure recovery of ETS Sousa, mortality due to human causes should be reduced to <1 individual every 7 yr. Fisheries bycatch is the most serious threat to these dolphins and needs to be eliminated as soon as possible to avoid extinction. Preventing the use of trammel nets, other gillnets and trawling throughout their habitat would be the single most effective conservation measure for ETS Sousa in the short term. Other fishing methods are available, and using the most selective, sustainable fishing methods available will benefit not only dolphins but also fish stocks, seabirds and other species, as well as the fishing industry, which depends on these species for its long-term viability. However, in the short term, there are costs associated with switching to more selective fishing gear.
Endangered Species Research 12/2013; 22:99-114. · 2.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: The conservation of humpback dolphins, distributed in coastal waters of the Indo-West Pacific and eastern Atlantic Oceans, has been hindered by a lack of understanding about the number of species in the genus (Sousa) and their population structure. To address this issue, we present a combined analysis of genetic and morphologic data collected from beach-cast, remote-biopsied and museum specimens from throughout the known Sousa range. We extracted genetic sequence data from 235 samples from extant populations and explored the mitochondrial control region and four nuclear introns through phylogenetic, population-level and population aggregation frameworks. In addition, 180 cranial specimens from the same geographical regions allowed comparisons of 24 morphological characters through multivariate analyses. The genetic and morphological data showed significant and concordant patterns of geographical segregation, which are typical for the kind of demographic isolation displayed by species units, across the Sousa genus distribution range. Based on our combined genetic and morphological analyses, there is convincing evidence for at least four species within the genus (S. teuszii in the Atlantic off West Africa, S. plumbea in the central and western Indian Ocean, S. chinensis in the eastern Indian and West Pacific Oceans, and a new as-yet-unnamed species off northern Australia).
[show abstract][hide abstract] ABSTRACT: 1. The global range of Risso's dolphin Grampus griseus is not well known, and there has been confusion in the literature as to whether the species has a broad, circumglobal range or only occurs along continental margins. 2. To clarify the species' distribution and habitat preferences, we compiled and reviewed all available (published and unpublished) records of sightings and cap-tures of this species for the past 62 years (1950–2012, n = 8068 records). Stranding records were not included. 3. The results showed that the species has a range that extends across ocean basins and spans between at least 64°N and 46°S, and is apparently absent from high-latitude polar waters. Although Risso's dolphins occur in all habitats from coastal to oceanic, they show a strong range-wide preference for mid-temperate waters of the continental shelf and slope between 30° and 45° latitude. 4. Although a number of misconceptions about the distributional ecology of Risso's dolphin have existed, this analysis showed that it is a widespread species. It strongly favours temperate waters and prefers continental shelf and slope waters to oceanic depths. These habitat preferences appear to hold throughout much or all of the species' range.
[show abstract][hide abstract] ABSTRACT: We studied life history characteristics of the Hong Kong/Pearl River Estuary population of Indo-Pacific humpback dolphins (Sousa chinensis), based on data from 120 specimens stranded between 1995 and 2009, 40 individuals biopsied at sea, and a long-term (14+ yr) photo-identification study. Ages were determined for 112 specimens by thin-sectioning teeth and counting growth layer groups. Estimated length at birth was 101 cm. Longevity was at least 38 yr, and there was little difference in growth patterns of males and females. Growth was described by a Bayesian two-phase Gompertz model; asymptotic length was reached at 249 cm. The tooth pulp cavity filled at an average of 18.5 yr of age. Physical maturity was reached at between 14 and 17 yr of age, apparently a few years after attainment of sexual maturity. Maximum lengths and weights of about 268 cm and 240 kg were attained. Females appear to lose all their spots by 30 yr, although males may retain some spotting throughout life. Calving occurred throughout the year, with a broad peak from March to June. Of 60 females monitored at sea for >14 yr of the study, none were documented to have more than three calves, suggestive of low reproductive output or low calf survival.
[show abstract][hide abstract] ABSTRACT: Atlantic humpback dolphins (Sousa teuszii) are endemic to nearshore West African waters between Western Sahara and Angola. They are considered Vulnerable by the International Union for Conservation of Nature based on restricted geographic range, low abundance and apparent decline in recent decades. We review the human activities most likely to affect the species and consider appropriate conservation actions. Bycatch (incidental capture) in gillnets is the greatest immediate threat. Deaths from entanglement have been documented in Mauritania, Senegal, Guinea-Bissau, Guinea and the Republic of the Congo. In Namibe Province, Angola, 4.8 artisanal fishing boats and two gillnets per km were observed in some areas within 1 km of the coast and gillnets are deployed regularly inside bays used by dolphins. Other concerns include the ‘marine bushmeat’ trade, habitat loss/degradation, overfishing, marine pollution, anthropogenic sound and climate change. Conservation challenges include a paucity of scientific data on the species, and widespread human poverty within most range states, resulting in high dependence on artisanal fisheries. Recommended conservation and research priorities include: (1) distribution and abundance surveys in known and potential range states, (2) bycatch monitoring programmes, (3) education/awareness schemes, and (4) protection of core areas via reduction/elimination of nearshore gillnetting.
[show abstract][hide abstract] ABSTRACT: The adoption of endangered species laws in various nations has intensified efforts to better understand, and protect, at-risk species or populations, and their habitats. In many countries, delineating a portion of a species' habitat as particularly worthy of protection has become a mantra of these laws. Unfortunately, the laws themselves often provide scientists and managers with few, if any, guidelines for how to define such habitat. Conservationists and scientists may view protecting part of the habitat of an endangered species as an ineffectual compromise, while managers may be under pressure to allow a range of human activities within the species' habitat. In the case of small cetaceans, establishing boundaries for such areas can also be complicated by their mobility, the fluid nature of their environment, and the often ephemeral nature of their habitat features. The convergence of multiple human impacts in coastal waters around the world is impacting many small cetaceans (and other species) that rely on these areas for feeding, reproducing, and resting. The ten guiding principles presented here provide a means to characterize the habitat needs of small, at-risk cetaceans, and serve as a basis for the delineation of 'priority habitat' boundaries. This conceptual approach should facilitate a constructive discourse between scientists and managers engaged in efforts to recover endangered species. The degree to which the recovery of an at-risk species can be reconciled with sustainable economic activity will depend in part on how well these principles are incorporated into the delineation of priority habitat.
[show abstract][hide abstract] ABSTRACT: Atlantic humpback dolphins (Sousa teuszii) are endemic to tropical coastal waters between Western Sahara and Angola, West Africa. They are classified as Vulnerable by the IUCN due to their restricted geographic range, low abundance and declining status. Seventy-one Atlantic humpback dolphin sightings were recorded along 55km of coast in Namibe Province, Angola, during two three-week periods in the summer and winter of 2008. Photo-identification documented 10 individuals, indicating low abundance of the Angola Management Stock. Most sightings (n=46, 65%) occurred in a restricted niche within 300m of shore rendering dolphins highly susceptible to anthropogenic impacts. Nearshore (
[show abstract][hide abstract] ABSTRACT: Due to indications that misidentification (largely confusion among dolphins of the genera Delphinus and Stenella) in the past had led to erroneous assumptions of distribution of the two species of common dolphins (Delphinus delphis and D. capensis) in the western Atlantic Ocean, we conducted a critical re-examination of records of the genus Delphinus from this region. We compiled 460 ‘plottable’ records, required support for confirmation of genus and species identifications,
and found many records lacking (and some clearly misidentified). When we plotted only the valid records (n=364), we found evidence of populations in only three areas, and apparent absence throughout much of the tropical/subtropical
regions. Off the east coast of the US and Canada, D. delphis is found from the Georgia/South Carolina border (32°N) north to about 47–50°N off Newfoundland. Since the 1960s, they have
apparently been absent from Florida waters. There is no evidence that dolphins of the genus occur in the Gulf of Mexico. Reports
of common dolphins from most of the Caribbean Basin are also rejected, and the only place in that region where they are confirmed
to occur is off central-eastern Venezuela (a coastal D. capensis population). Off eastern South America, common dolphins appear to be restricted to south of 20°S. There is a coastal long-beaked
population found in the South Brazil Bight, and one or more short-beaked populations south and offshore of this (ranging south
to at least northern Argentina). The results are very different from commonly-accepted patterns of distribution for the genus
in the Atlantic. Most areas of distribution coincide with moderate to strong upwelling and common dolphins appear to avoid
warm, tropical waters. This study shows that great care must be taken in identification of similar-appearing long-beaked delphinids,
and that uncritical acceptance of records at face value can lead to incorrect assumptions about the ranges of the species
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action.
[show abstract][hide abstract] ABSTRACT: Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive
assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all
5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but
suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher
among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are
spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately
poorly known. These data are made freely available to support further scientific developments and conservation action.
[show abstract][hide abstract] ABSTRACT: A diastereoisomer (alpha, beta, and gamma) specific analytical method for measuring hexabromocyclododecanes (HBCDs) was developed using liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method developed was applied to analyze blubber of small cetaceans to divulge the distribution and temporal variation of HBCDs in the Asian marine environment. HBCDs were detected in all the blubber samples of finless porpoises (Neophocaena phocaenoides) and Indo-Pacific humpback dolphins (Sousa chinensis) collected from the South China Sea during 1990-2001. Concentrations of HBCDs were higher in humpback dolphins (31-380 ng/g lipid) than in finless porpoises (4.7-55 ng/g lipid), which can be attributed to habitat differences. Average concentrations of alpha-HBCD in finless porpoises increased from 9.5 ng/g lipid in 1990 to 35 ng/g lipid in 2000/01. alpha-HBCD was predominant among the three isomers with some exceptions in finless porpoises collected in 1990. This is the first report on HBCDs contamination in marine mammals from Southeast Asia.
[show abstract][hide abstract] ABSTRACT: The potential health risks due to inorganic substances, mainly metals, was evaluated for the two resident marine mammals in Hong Kong, the Indo-Pacific Humpback Dolphin (Sousa chinensis) and the Finless Porpoise (Neophocaena phocaenoides). The stomachs from the carcasses of twelve stranded dolphins and fifteen stranded porpoises were collected and the contents examined. Concentrations of thirteen trace elements (Ag, As, Cd, Co, Cr, Cs, Cu, Hg, Mn, Ni, Se, V and Zn) were determined by inductively coupled plasma mass spectrometer (ICP-MS). An assessment of risks of adverse effects was undertaken using two toxicity guideline values, namely the Reference Dose (RfD), commonly used in human health risk assessment, and the Toxicity Reference Value (TRV), based on terrestrial mammal data. The levels of trace metals in stomach contents of dolphins and porpoises were found to be similar. Risk quotients (RQ) calculated for the trace elements showed that risks to the dolphins and porpoises were generally low and within safe limits using the values based on the TRV, which are less conservative than those based on the RfD values. Using the RfD-based values the risks associated with arsenic, cadmium, chromium, copper, nickel and mercury were comparatively higher. The highest RQ was associated with arsenic, however, most of the arsenic in marine organisms should be in the non-toxic organic form, and thus the calculated risk is likely to be overestimated.
[show abstract][hide abstract] ABSTRACT: In 2002, a small population of Indo-Pacific humpback dolphins, Sousa chinensis, was discovered in the coastal waters of the eastern Taiwan Strait. Serious conservation concerns about this population led to a survey of most of the coastal waters of western Taiwan to better under- stand the status of this population. Surveys were con- ducted from boats (inshore waters) and a sea-kayak or land-based platforms (littoral waters inshore of large sandbars). Humpback dolphins were sighted 35 times, all within a stretch of inshore waters approximately 100 km (linear distance) and within 2 km from shore (none were observed in littoral waters). Including consid- eration of other records of this species, the main distri- bution of these dolphins was estimated to be approximately 515 km2 of water off central western Taiwan, where industrialization is a serious and rapidly increasing issue. The population's abundance and den- sity were estimated to be 99 individuals (coefficient of variation 51.6%) and 19.3 individuals/100 km 2 , respect- ively, which is quite low when compared to the Pearl River estuary population. Assessing this population using the IUCN Red List criteria resulted in a ''Critically Endan- gered'' categorization, reinforcing the urgency of the situation.