Humpback Dolphins Research Articles

Risk assessment of phthalate metabolites accumulated in fish to the Indo-Pacific humpback dolphins from their largest habitat

Food has consistently been shown to be an important source of exposure to environmental pollutants, drawing attention to the health risks of pollutants in marine mammals with high daily food intake. Here, the dietary exposure risks posed to the Indo-Pacific humpback dolphins from the Pearl River Estuary (PRE), China, by fourteen phthalate metabolites (mPAEs) were evaluated for the first time. On the basis of liquid chromatography-mass spectrometry (LC-MS/MS) analysis, the levels of ∑14mPAEs in ten main species of prey fish (n = 120) of dolphins ranged from 103.0 to 444.5 ng/g wet weight (ww), among which Bombay duck contained a significantly higher body burden of ∑14mPAEs than other prey species. Phthalic acid (PA), monooctyl phthalate (MnOP), monononyl phthalate (MNP), monoethyl phthalate (MEP), monoethylhexyl phthalate (MEHP), mono (5-carboxy-2-ethylpentyl) phthalate (MECPP), monobutyl phthalate (MBP), and monoisobutyl phthalate (MiBP) all had a trophic magnification factor (TMF) greater than unity, indicating the biomagnification potential of these mPAEs in the marine ecosystem of the PRE. A dietary exposure assessment based on the adjusted reference dose values of phthalates (PAEs) showed that bis (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) may pose a high (HQ > 1) and medium (0.01 < HQ < 1) risk to the dolphin adults and juveniles, respectively. Our results highlight the potential health risks of mPAEs to marine mammals through dietary routes.

Modeling Suitable Habitats of Indo-Pacific Humpback Dolphins (Sousa chinensis) in a Highly Urbanized Bay

Indo-Pacific humpback dolphins (Sousa chinensis) live in coastal waters that have experienced considerable anthropogenic disturbances. Specifically, along the coasts of highly urbanized regions, available habitats have decreased in both space and scale. This study used Maxent software to simulate the distribution of suitable habitats for S. chinensis during the dry and wet seasons in Xiamen Bay. We also aimed to identify key environmental factors influencing habitat distribution, with the goal of using our results to analyze conservation gaps and propose adjustments. We found that during the dry season, S. chinensis were mainly distributed in the Western Harbor, Jiulong River Estuary, and the mouth of Tongan Bay. During the wet season, they were distributed in the south of Western Harbor, Jiulong River Estuary, and around the Wuyu and Dadeng-Xiaodeng Islands. Nekton density, chlorophyll-a concentration, sea surface temperature, slope, and salinity are the primary factors affecting S. chinensis distribution in Xiamen Bay. To better protect the species, the existing Tongan Bay reserve should be expanded during dry seasons, and suitable habitats in the Jiulong River Estuary should be turned into a seasonal protected region. Similarly, during wet seasons, the original Western Harbor portion of the reserve should increase to include the Jiulong River Estuary, northwest of the Wuyu Islands and south of the Dadeng-Xiaodeng Islands. In addition to this dynamic seasonal management of reserve size, we also recommend developing multiple-use protected areas and establishing a joint protection mechanism between local governments. In conclusion, our model offers important guidance on improving conservation measures of S. chinensis in Xiamen Bay.

Strandings, mortality and morbidity of Indo-Pacific humpback dolphins in Hong Kong, with emphasis on the role of organochlorine contaminants

Factors related to mortality and disease in Indo-Pacific humpback dolphins (Sousa chinensis) from Hong Kong waters were investigated by detailed examination of dolphin specimens found stranded from 1995-2004. In total, 86 specimens were necropsied, but many of these were too badly decomposed to provide much information. Skin and blubber biopsies were also collected from six identified living individuals and concentrations of organochlorines (DDTs, PCBs and HCHs) were determined from blubber samples of stranded and biopsied dolphins. A large proportion of the strandings (53.2%) were young-of-the-year. The most commonly diagnosed causes of death were net entanglement and vessel collision. The pesticide DDT showed the highest concentrations and the ratio of DDT to its breakdown products (and other information) suggests that there may be a recent or nearby source of DDT into the dolphins’ ecosystem. Concentrations of both DDTs and PCBs showed a pattern of increasing with age in males. In females, they increased until sexual maturity, then decreased, and finally increased again in late life. This is consistent with a hypothesised transfer of pollutants from mother to offspring during gestation and lactation. Inter-laboratory differences and effects of decomposition of specimens are two potential biases that may significantly affect the quality of the present data. In order to resolve the potential problems associated with these issues, a long-term biopsy collection programme has recently been initiated.

Population distribution, connectivity and differentiation of Indo‐Pacific humpback dolphins in Chinese waters: Key baselines for improving conservation management

Abstract Humpback dolphins (Sousa spp.), throughout their distribution ranges, are often designated as flagship species for coastal ecosystem conservation. Most of the early research on humpback dolphins was carried out in Chinese waters, and in the last two decades, numerous studies have provided abundant conservation‐valuable findings. In this study, a systematic review was conducted to gain a comprehensive understanding of the distributional ecology of humpback dolphins in Chinese waters, to establish an updated national knowledge base about key conservation baselines on this flagship species. Currently, there are at least eight main distribution areas of humpback dolphins along the coast of southern China, representing a clear picture of place‐based conservation units. However, the overall biogeographical distribution pattern is discontinuous, and existing marine protected areas are far from sufficient to protect these key areas for the survival of humpback dolphins. Based on the photo‐identification technique, cross‐matching of humpback dolphin individuals revealed extremely low inter‐population connectivity among most of the known populations. Genetic studies suggested that several examined populations have low haplotype diversity levels, with limited inter‐population gene flow. Morphological and behavioural evidence also supports population differentiation among geographical locations. These findings provide key baselines for the promotion of conservation management initiatives for humpback dolphins in Chinese waters. All recognizable geographical populations, together with each key habitat, should be considered as independent conservation units. With small distribution areas, low genetic diversity and unfavourable geographical isolation, several populations may be at a high risk of regional extinction. A country‐led scheme with cross‐regional collaboration is required for science‐based, action‐focused and timely conservation efforts. Future conservation management initiatives should aim to increase or at least maintain key habitats, inter‐population connectivity, population‐level genetic diversity and effective population size.

Habitat partitioning, co-occurrence patterns, and mixed-species group formation in sympatric delphinids

Numerous species have been reported to form mixed-species groups, however, little is known about the interplay between niche partitioning and mixed-species group formation. Furthermore, it is often unclear whether species come together by chance due to overlapping habitat preferences, by shared attraction to resources, or by attraction between them. We assessed habitat partitioning, co-occurrence patterns, and mixed-species group formation of sympatric Australian humpback (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) around the North West Cape, Western Australia, with a joint species distribution model and temporal analyses of sighting data. Australian humpback dolphins preferred shallower and more nearshore waters than Indo-Pacific bottlenose dolphins, yet these species co-occurred more often than expected by chance given shared responses to environmental variables. Indo-Pacific bottlenose dolphins were sighted more often than Australian humpback dolphins during the afternoon, however, we did not find any temporal patterns in the occurrence of mixed-species groups. We propose that the positive association in the species’ occurrence indicates the active formation of mixed-species groups. By evaluating habitat partitioning and co-occurrence patterns, this study provides direction for future work which should proceed to investigate the benefits that these species may gain from grouping with each other.

Estimation of Per- and Polyfluorinated Alkyl Substance Induction Equivalency Factors for Humpback Dolphins by Transactivation Potencies of Peroxisome Proliferator-Activated Receptors.

The potential risks of per- and polyfluoroalkyl substance (PFAS) accumulation in nearshore dolphins are not well understood. Here, transcriptional activities of 12 PFAS on peroxisome proliferator-activated receptors (PPAR-α, -β/δ, and -γ) in Indo-Pacific humpback dolphins (Sousa chinensis) were evaluated. All PFAS activated scPPAR-α in a dose-dependent manner. PFHpA exhibited the highest induction equivalency factors (IEFs). The order of IEFs for other PFAS was as follows: PFOA > PFNA > PFHxA > PFPeA > PFHxS > PFBA > PFOS > PFBuS ≈ PFDA ≫ PFUnDA and PFDoDA (not activated). The total induction equivalents (∑IEQs, 5537 ng/g wet weight) indicated that more attention should be paid to investigating contamination levels in dolphins, especially in PFOS (82.8% contribution to the ∑IEQs). The scPPAR-β/δ and -γ were not affected by any PFAS, except for PFOS, PFNA, and PFDA. Furthermore, PFNA and PFDA could induce higher PPAR-β/δ and PPAR-γ-mediated transcriptional activities than PFOA. Compared to human beings, PFAS might be more potent PPAR-α activators in humpback dolphins, suggesting that the dolphins may be more susceptible to the adverse effects of PFAS. Our results may be instructive for understanding the impacts of PFAS on marine mammal health due to the identical PPAR ligand-binding domain.

Occurrence and distribution of cetaceans off northern Angola, 2004/05

The occurrence and distribution of cetacean species off northern Angola was examined using dedicated survey data and incidental sighting records. Dedicated surveys for cetaceans were carried out during two geophysical seismic surveys off northern Angola between August 2004 and September 2005. A total of 3,268hr of survey effort data were collected, resulting in 779 on-effort cetacean sightings. There were 263 sightings reported off-effort and incidentally from other platforms and sports fishermen. With 21 cetacean species confirmed, the cetacean community off northern Angola is diverse and primarily tropical in characteristic, comprising four species of baleen whale, two sperm whale species, at least two beaked whale species, and 13 species of delphinid. Humpback and sperm whales were the most frequently recorded cetaceans. The occurrence of humpback whales was significantly higher within neritic waters, and during the winter and spring months in association with seasonal occupancy of their West African breeding grounds. Sperm whales were recorded in water depths exceeding 1,000m and demonstrated significant seasonality, with peak occurrence during the summer and autumn. Atlantic spotted dolphins and common dolphins (Delphinus sp.) were the most numerous delphinids recorded, with spotted dolphins showing a significant seasonal peak during the spring and summer, and common dolphins in the winter. Other species recorded included fin whale, sei whale, Bryde’s whale, dwarf sperm whale, Cuvier’s and Mesoplodon beaked whales, killer whale, short-finned pilot whale, false killer whale, melon-headed whale, Atlantic humpback dolphin, rough-toothed dolphin, Risso’s dolphin, bottlenose dolphin, Pantropical spotted dolphin, spinner dolphin, Clymene dolphin and striped dolphin. Further research is required to document the cetacean community in Angola, particularly given the unknown threat from fishery bycatch and the increasing level of oil and gas exploration in the region.

Elements in muscle tissue of three dolphin species from the east coast of South Africa

We investigated elemental concentrations in muscle tissue of three species of dolphins incidentally bycaught off the KwaZulu-Natal coastline, South Africa. Thirty-six major, minor and trace elements were analysed in Indian Ocean humpback dolphin Sousa plumbea (n = 36), Indo-Pacific bottlenose dolphin Tursiops aduncus (n = 32) and the Common dolphin Delphinus delphis (n = 8). Significant differences in concentration between the three species were observed for 11 elements (cadmium, iron, manganese, sodium, platinum, antimony, selenium, strontium, uranium, vanadium and zinc). Mercury concentrations (maximum 29 mg/kg dry mass) were generally higher than those reported for coastal dolphin species found elsewhere. Our results reflect a combination of species differences in habitat, feeding ecology, age, and possibly species physiology and exposure to pollution levels. This study confirms the high organic pollutant concentrations documented previously for these species from the same location, and provides a well-founded case for the need to reduce pollutant sources.

Species occurrence and distributional ecology of nearshore cetaceans in the Bay of Bengal, Bangladesh, with abundance estimates for Irrawaddy dolphins Orcaella brevirostris and finless porpoises Neophocaena phocaenoides

A vessel-based line-transect survey conducted during February 2004 along 1,018km of systematic trackline in the nearshore waters of Bangladesh resulted in 111 ‘on-effort’ cetacean sightings including: Irrawaddy dolphins, Orcaella brevirostris (n=75, mean group size=2.2); finless porpoises, Neophocaena phocaenoides (n=11, mean group size=2.6); Indo-Pacific humpback dolphins, Sousa chinensis (chinensisform; n=6, mean group size=16.2); Indo-Pacific bottlenose dolphins, Tursiops aduncus (n=3, mean group size=36.1); pantropical spotted dolphins, Stenella attenuata (n=1, best, high and low group size estimates=800, 1,100 and 600, respectively); Bryde’s whales, Balaenoptera edeni/brydei (large-form; n=1, three individuals); and unidentified small cetaceans (n=14). Cetacean distribution was closely tied to environmental gradients, with Irrawaddy dolphins and finless porpoises occurring most often in nearshore, turbid, low-salinity waters, IndoPacific humpback dolphins in slightly deeper waters where the colour turned from brown to green and Indo-Pacific bottlenose dolphins and Bryde’s whales in deep, clear, high-salinity waters of the Swatch-of-No-Ground (SoNG), a 900+m-deep submarine canyon that extends to within about 40km of the Sundarbans mangrove forest. A Generalised Additive Model of environmental and presence-absence data indicated that Irrawaddy dolphin distribution was conditionally dependent (p&lt;0.05) on low salinity and shallow depth, which explained 36% of the variance. A distance analysis of Irrawaddy dolphin and finless porpoise sightings resulted in abundance estimates of 5,383 (CV=39.5) and 1,382 (CV=54.8%), respectively. The positive conservation implications of these abundance estimates were tempered by observations of potentially unsustainable bycatch in gillnet fisheries targeting elasmobranches and scarring on bottlenose dolphins consistent with trawl fishery interactions. The nearshore waters of Bangladesh support a taxonomically diverse and relatively abundant cetacean fauna, which can probably be explained by the wide variety of environmental gradients (river-sea and shallow-deep) available within a relatively small area and the enormous biological production driven by extreme fluvial and oceanographic processes. Priority recommendations for future research include: (1) evaluating bycatch levels and the types of fishing gears responsible for incidental kills; (2) investigating the spatial and temporal dynamics of high-density cetacean hotspots; (3) resolving the species and population identities of baleen whales and delphinids occurring in the SoNG; and (4) assessing the abundance, movement patterns and fishery interactions of Indo-Pacific bottlenose dolphins.

A note on the species occurrence, distributional ecology and fisheries interactions of cetaceans in the Mergui (Myeik) Archipelago, Myanmar

A vessel-based line-transect survey for cetaceans conducted during 23 February-6 March 2005 of the nearshore waters (to a depth of 40- 60m) of the Mergui (Myeik) Archipelago of southern Myanmar searched along 955km of trackline resulting in 30 cetacean sightings. These included Indo-Pacific bottlenose dolphins Tursiops aduncus (n=15), Indo-Pacific humpback dolphins Sousa chinensis (n=3), spinner dolphins Stenella longirostris (n=4; the largest of these was mixed with pantropical spotted dolphins Stenella attenuata), Irrawaddy dolphins Orcaella brevirostris (n=1), finless porpoises Neophocaena phocaenoides (n=1), Bryde’s whales Balaenoptera edeni/brydei (identification tentative; n=1), one unidentified baleen whale (probably also a Bryde’s whale) and four unidentified delphinid groups. Irrawaddy dolphins and finless porpoises were found in shallow, brackish waters, Indo-Pacific humpback dolphins also in shallow waters but those less affected by freshwater inputs and Bryde’s whales and Indo-Pacific bottlenose, spinner and spotted dolphins in deeper and clearer waters. In total 2,565 gill netters/long liners (95% CI=1,228-3,903), 1,301 squid jiggers (95% CI=611-1,992) and 532 stern trawlers (95% CI=154-910) were estimated to be operating in the study area. Concentrations of gill netters/long liners were particularly high in shallow nearshore waters and at least 150 were operating in the bay where the only sightings of Irrawaddy dolphins and finless porpoises were made. There is a need to better assess nearshore cetacean populations, investigate whether or not incidental and intentional catches are sustainable and incorporate a cetacean element into an initiative to establish a marine protected area network in the Mergui Archipelago.

A note on cetacean distribution in the Indian EEZ and contiguous seas during 2003-07

Relatively little is known about the distribution of cetaceans in Indian seas due to lack of systematic surveys. For collecting data on species distribution, 35 opportunistic surveys were conducted onboard FORV Sagar Sampada between October 2003 and February 2007 in the Indian EEZ and contiguous seas. In 5,254 hours of sighting effort, a total of 473 cetacean records were made with 5,865 individuals. The occurrence of 10 species from three cetacean families was confirmed. The Indo-Pacific bottlenose dolphin was the most frequently sighted species, whereas the spinner dolphin was dominant in terms of abundance. Long-beaked common dolphins, Indo-Pacific hump-backed dolphin and sperm whales were also recorded at frequent intervals. Cetaceans were found to have a wide geographical distribution in the Indian EEZ and contiguous seas. High abundance and species richness were recorded in the Southeastern Arabian Sea and southern Sri Lankan waters. From the information collected during the present study, the platform of opportunity has proved to be a useful means for cetacean survey.

Cetacean distribution in the coastal waters of the Sultanate of Oman

Small boat surveys were conducted between 2000 and 2003 in three main regions of Oman’s coastal waters: Muscat, the Gulf of Masirah and Dhofar. Survey data were analysed to calculate relative abundances of the seven most frequently encountered species in these areas. These include (in order of frequency) bottlenose dolphins (Tursiops sp.), long-beaked common dolphins (Delphinus capensis), humpback whales (Megaptera novaeangliae), spinner dolphins (Stenella longirostris), Indo-Pacific humpback dolphins (Sousa chinensis), Bryde’s whales (Balaenoptera sp.) and Risso’s dolphins (Grampus griseus). Other species observed include false killer whales (Pseudorca crassidens), blue whales (Balaenoptera musculus), rough-toothed dolphins (Steno bredanensis) and unidentified beaked whales. Encounter rates per distance searched were plotted by 0.1 x 0.1 degree grid cell, giving an indication of relative abundances and key areas of habitat used by each of the seven most frequently encountered species. These plots demonstrate that the nearshore areas of the Gulf of Masirah, as well as the coastal waters of Dhofar, are areas of concentration for the Arabian Sea’s recently designated Endangered subpopulation of humpback whales, as well as Indo-Pacific humpback dolphins, which are considered Near Threatened on the IUCN Red List of Threatened Species.1 The results presented here provide valuable baseline data for future research and help to inform conservation management efforts that are required to address the highly vulnerable status of the humpback whale and Indo-Pacific humpback dolphin populations in question.

Marine mammal records from Iran

Iran has 1,700km of coastline that borders the Persian Gulf and the Arabian Sea in the northwest Indian Ocean. Apart from a handful of records, almost nothing is known about which marine mammal species occur in Iranian waters. This review was conducted to fill this information gap. A total of 127 marine mammal records of 14 species were compiled from Iranian coastal waters. Ninety-nine were from the Persian Gulf, 26 from the Gulf of Oman and 2 were of unknown location. Records of finless porpoise (Neophocaena phocaenoides) (25), Indo-Pacific humpback dolphin (Sousa chinensis) (24) and Indo-Pacific bottlenose dolphin (Tursiops aduncus) (22) were by far the most numerous, a probable reflection of their inshore distribution and local abundance. Other species recorded were long-beaked common dolphin (Delphinus capensis tropicalis), roughtoothed dolphin (Steno bredanensis), striped dolphin (Stenella coeruleoalba), spinner dolphin (Stenella longirostris), Risso’s dolphin (Grampus griseus), false killer whale (Pseudorca crassidens), sperm whale (Physeter macrocephalus) and dugong (Dugong dugon). Records of 26 mysticetes were compiled, 10 of which were tentatively identified as Bryde’s whales (Balaenoptera edeni), 1 possible fin whale (Balaenoptera physalus), 3 humpback whales (Megaptera novaeangliae) and the remainder were not identified to species. The largest threat to small cetaceans in Iran is likely to be incidental capture in fishing gear. Nine finless porpoises were recorded as bycatch and this and other coastal species may be declining due to unsustainable mortality rates. Some of the world’s busiest shipping lanes pass through Iranian waters and ship strikes are likely to be the largest threat to mysticetes in the area.

Skin Marks in Critically Endangered Taiwanese Humpback Dolphins (Sousa chinensis taiwanensis).

As long-lived apex predators, Indo-Pacific humpback dolphins (Sousa chinensis) are key indicators of marine coastal environmental health. Skin marks can be observed on dorsal body surfaces that are visible during mark-recapture studies that rely on photo-identification (photo-ID) methods. Skin mark prevalence may be an indicator of environmental or anthropogenic stressors in the ecosystem, which may lead to individual and/or population-level health concerns. The prevalence of marks of anthropogenic origin was assessed in the Critically Endangered S. chinensis taiwanensis population along the coasts of central Taiwan. Fifty, twenty-eight, and thirty-four individuals were identified in 2018, 2019, and 2021, respectively. At least one category of injuries was observed in 47 of 57 distinctive individuals (82%), and adults showed a higher prevalence of deep injuries than the other coloration stages. At least one category of skin lesion was observed in 33 of 57 distinctive individuals (58%), and high prevalence of skin lesions was found in mature individuals. Given the difficulty in taking direct observations, skin mark prevalence is proposed as a proxy for estimating habitat health and anthropogenic stressors upon S. chinensis taiwanensis. The moderate-to-high prevalence of skin marks in this study was designated as a warning of risks. This study provides important updated information for the assessment of the health and survival of this population. More effective management measures are urgently needed to reverse the observed population decline.

Recent records of marine mammals in Tanzanian waters

Marine mammal species diversity off Zanzibar and Tanzania, East Africa, has been recorded by the Marine Mammal Education and Research Group at the Institute of Marine Sciences, Zanzibar, Tanzania since 1998. The data presented in this report reflect the efforts of 10 years collection of information from marine mammals stranded and incidentally caught in Tanzanian waters. Additional information from dedicated surveys of cetaceans (whales and dolphins) and incidental sightings reported by the general public are also provided. From 1992 through 2008 a total of 235 specimens of 13 cetacean species and the dugong were recorded. 214 (90.7%) records referred to specimens from bycatch in drift and bottom-set gillnets and 22 (9.3%) referred to specimens from strandings. Based on incidental catch and sightings records, Indo-Pacific bottlenose, spinner and Indo-Pacific humpback dolphins, observed year-round, and humpback whales, observed seasonally during July to November, were the most common species in Tanzanian coastal waters.

Occurrence of whales and dolphins in Pakistan with reference to fishers’ knowledge and impacts

This paper reports the findings of a project (Cetacean Conservation Pakistan) launched in 2004 with a view to: (a) undertaking quantitative surveys to determine the variety and abundance of species present; (b) working with local fisher communities to collate local knowledge and promote public awareness; and (c) promoting a marine cetacean conservation strategy and measures. Boat-based surveys for live animals and shore surveys for beachcast specimens have confirmed the presence of twelve species of whale and dolphin. Among these bottlenose dolphins (Tursiops sp.) occur both inshore along the coasts of Sindh and Balochistan, and offshore in parts of Balochistan; these two populations possibly representing different sub-species. Indo-Pacific humpback dolphins (Sousa chinensis) are common inshore around the mouth of the Indus Delta and in large sheltered bays in Balochistan, where finless porpoise (Neophocaena phocaenoides) also occur. Spinner dolphins (Stenella longirostris) were observed in very large schools (up to 2,000) around the shelf edge in eastern Balochistan, as were Risso’s dolphins (Grampus griseus) in smaller numbers. Common dolphins (Delphinus capensis) were recorded even further offshore. There were two sightings of humpback whales (Megaptera novaeangliae), and one of a killer whale (Orcinus orca). Bryde’s whales (Balaenoptera edeni), sperm whales (Physeter macrocephalus) and Cuvier’s beaked whales (Ziphius cavirostris) were recorded only during beach surveys, while skeletal remains in institutions also supported the occurrence of blue whales (Balaenoptera musculus). Work with local fisher communities supported this picture of species distribution and provided information on threats to local cetaceans. These are principally occasional entanglement in fishing gear and opportunistic exploitation for use as food, as bait, as medicine or for other purposes. The project incorporated policy development and the preparation of a marine cetacean biodiversity action plan that included the listing of species in provincial conservation legislation, the designation of a marine protected area in Balochistan, the establishment of a national whale and dolphin conservation society, and trials of whale and dolphin watching as a means of raising public awareness and providing alternative economic value.

Organ weights of three dolphin species (Sousa chinensis, Tursiops aduncus and Delphinus capensis) from South Africa: implications for ecological adaptation?

Data from bycaught, but otherwise presumed healthy individuals can contribute important biological data on species of cetaceans that are otherwise lacking. This study utilises data collected from systematic necropsies performed between October 1970 and May 2010 on 142 Indo-Pacific humpback dolphins (Sousa chinensis), 607 Indo-Pacific bottlenose dolphins (Tursiops aduncus), and 640 long-beaked common dolphins (Delphinus capensis) incidentally caught and drowned in the shark nets off KwaZulu-Natal, South Africa. The aim of this analysis was to: (1) determine average absolute and relative organ weights for the three taxa as baseline values for later pathological examinations; and (2) examine potential correlations with the physiology and ecology in the three genera. Body length-weight relationships were described for the three species, indicating that S. chinensis is more robust than T. aduncus, with D. capensis being the smallest species out of the three taxa. Organ weights, as a percentage of total body weight were examined for the three delphinids. Organs examined included heart, lungs and trachea, liver, kidneys, spleen, and testes. Relative heart, liver and kidney weights were significantly larger in the small-bodied, fast-swimming D. capensis, than in the slower, more coastal S. chinensis and T. aduncus, possibly reflecting differences in activity patterns between the three species. Relative lung and trachea weights were not significantly different in the three species. Combined testes weight, as a percentage of total body weight, in combination with information on group size and sexual dimorphism suggested a monogamous or extreme polygynous (harem) mating system in S. chinensis, frequent copulations in T. aduncus, and sperm competition in D. capensis. The results of the present study suggest that the relative sizes of the major organs in the three genera are a reflection of the differing life histories and ecologies of the species examined.

Suitable habitats of two coastal cetaceans along the northern Arabian Sea: Important marine mammal areas susceptible to conservation gaps

Abstract Coastal cetaceans are often selected as a biodiversity surrogate in ecosystem‐based conservation planning. In the northern Arabian Sea there is insufficient information on suitable habitats for the Indo‐Pacific finless porpoise and Indian Ocean humpback dolphin for planning protection. Suitable habitats for the Indo‐Pacific finless porpoise and Indian Ocean humpback dolphin were projected using the MaxEnt model in the present study. The variable contributions in MaxEnt exercises and characteristics of the major habitats were used to represent the ecological niches of these two cetaceans. Along coastal waters of the northern Arabian Sea, bathymetry was the most significant variable that influenced the distribution of the Indian Ocean humpback dolphin, which prefers water 2–5 m deep. The Indo‐Pacific finless porpoise prefers 6–20 m deep water and its distribution was influenced by bathymetry, sea‐surface temperature and chlorophyll‐a concentration. Suitable habitats identified by this study provide a baseline from which to evaluate the impact of anthropogenic activities in coastal and estuarine waters, assist marine development planning and guide marine protected area (MPA) designations. Effective MPA designation would include ca. 30% of major habitats to accommodate viable populations and sufficient biodiversity richness to maintain a functioning ecosystem. Data used in the present study may be subject to sampling heterogeneity and thus coastal waters not included as suitable habitats would require further investigation for possible omission bias. Actions necessary for conservation of the Indo‐Pacific finless porpoise and Indian Ocean humpback dolphin include designating no‐take zones or MPAs, banning industrial fishing while restricting artisanal fishery activity and mobilizing community‐based conservation campaigns for major habitat protection. As such, further data on distribution, density and environmental variables related to cetaceans are needed to inform any conservation efforts.

Anomalous Coloration of Indo-Pacific Humpback Dolphins off Southern China

The Indo-Pacific humpback dolphin is characterized by a particular ontogenic change in body color from dark gray at birth to pure white (or with a few dark-gray spots) after reaching adulthood. Here, we report a spectrum of anomalous body color patterns observed on Indo-Pacific humpback dolphins off southern China. The occurrence of hypopigmentation and hyperpigmentation was described and compared among six putative dolphin populations. Low rates of anomalies in body color patterns were observed (&lt;1%), except for hypopigmentation, which was prevalent in dolphins residing in the mid-Pearl-River-Delta region (3.3%).

Delphinids of southern Africa: A review of their distribution, status and life history

Eighteen species of delphinids have been recorded from Africa, south of l 7°S. This review includes analyses of the distribution and status, life history and feeding habits for each species, primarily using published data from strandings, incidentally caught animals and sightings. Although there is little known for most of the species distributed over the continental shelf, it appears that there is presently little human-induced threat to these. However, more research emphasis should in future be placed on possible detrimental interactions due to overfishing of delphinid prey stocks. Increased commercial fishing pressure will inevitably also increase interactions between the fishery and the affected delphinids. Only three inshore species are presently considered to be vulnerable: Heaviside's dolphins (Cephalorhynchus heavisidil), bottlenose dolphins (Tursiops truncatus) in KwaZulu-Natal and Namibia, and Inda-Pacific hump-backed dolphins (Sousa chinensis) in KwaZulu-Natal. Heaviside's dolphins are endemic and, although presently probably able to sustain mortalities following interactions with commercial fishing gear, may become negatively impacted should fishing activities increase. The bottlenose dolphin population in Namibia appears localised in its distribution and may therefore also be vulnerable to any future coastal development or commercial fishery expansions, while in KwaZulu-Natal they are subjected to ongoing incidental catches in shark nets, heavy pollution levels, habitat destruction and increased competition with fishermen for limited food resources. In KwaZulu-Natal, Inda-Pacific hump-backed dolphins are subjected to the same pressures as experienced by bottlenose dolphins, albeit more severely, while in Mozambique it is occasionally caught incidentally in gillnets or in a targeted fishery. Although generally considered an offshore species, southern right whale dolphins (Lissodelphis peronii) also appears to be extremely localised in distribution within southern Africa, and any future planned expansion of commercial driftnet fisheries off Namibia should be carefully monitored for incidental catches which may impact this population.