Inshore Dolphins Research Articles

Hepatic concentrations of per- and polyfluoroalkyl substances (PFAS) in dolphins from south-east Australia: Highest reported globally

Per- and polyfluoroalkyl substances (PFAS) concentrations were investigated in hepatic tissue of four dolphin species stranded along the south-east coast of Australia between 2006 and 2021; Burrunan dolphin (Tursiops australis), common bottlenose dolphin (Tursiops truncatus), Indo-Pacific bottlenose dolphin (Tursiops aduncus), and short-beaked common dolphin (Delphinus delphis). Two Burrunan dolphin populations represented in the dataset have the highest reported global population concentrations of ∑25PFAS (Port Phillip Bay median 9750 ng/g ww, n = 3, and Gippsland Lakes median 3560 ng/g ww, n = 8), which were 50–100 times higher than the other species reported here; common bottlenose dolphin (50 ng/g ww, n = 9), Indo-Pacific bottlenose dolphin (80 ng/g ww, n = 1), and short-beaked common dolphin (61 ng/g ww, n = 12). Also included in the results is the highest reported individual ∑25PFAS (19,500 ng/g ww) and PFOS (18,700 ng/g ww) concentrations, at almost 30 % higher than any other Cetacea reported globally.Perfluorooctane sulfonate (PFOS) was above method reporting limits for all samples (range; 5.3–18,700 ng/g ww), and constituted the highest contribution to overall ∑PFAS burdens with between 47 % and 99 % of the profile across the dataset. The concentrations of PFOS exceed published tentative critical concentrations (677–775 ng/g) in 42 % of all dolphins and 90 % of the critically endangered Burrunan dolphin.This research reports for the first time novel and emerging PFASs such as 6:2 Cl-PFESA, PFMPA, PFEECH and FBSA in marine mammals of the southern hemisphere, with high detection rates across the dataset. It is the first study to show the occurrence of PFAS in the tissues of multiple species of Cetacea from the Australasian region, demonstrating high global concentrations for inshore dolphins. Finally, it provides key baseline knowledge to the potential exposure and bioaccumulation of PFAS compounds within the coastal environment of south-east Australia.

The first baleen whale marine protected area proposed for Bryde's whales in the Beibu Gulf, China

AbstractThe establishment of marine protected areas (MPAs) for cetaceans is an important strategy to mitigate human disturbance and protect biodiversity. Despite abundant cetacean species, there are only a few MPAs dedicated to cetacean conservation in China, all of which are for inshore dolphins. Bryde's whales, the only nearshore baleen whale population in mainland China, are conflicting with intensive human activities, yet an effective conservation strategy is lacking. This study used species distribution models to analyze distribution patterns and suitable habitats of Bryde's whales in the Beibu Gulf and proposes the first baleen whale MPA in China. Our results showed Bryde's whales have a seasonal distribution pattern in the Beibu Gulf, and that the waters around Weizhou Island and the southeastern coast of Vietnam were their core habitats. The seasonal nighttime light data indicated a negative relationship between the number of ship lights and Bryde's whale sightings and suggest that Bryde's whales might be threatened by fisheries. We proposed an MPA based on the results, suggesting that the waters within 20 km around Weizhou Island should be declared a protected area. Furthermore, we recommend that anthropogenic activities in the waters around Weizhou Island are better managed to reduce negative impacts on marine life.

Multiple social benefits drive the formation of mixed-species groups of Australian humpback and Indo-Pacific bottlenose dolphins

Mixed-species groups are common amongst diverse taxa including fishes, birds, and mammals. Antipredator, foraging, and social benefits have been proposed as functional explanations for mixed-species group formation. Amongst delphinids, mixed-species groups are widespread, but little is known about their function. To investigate the potential benefits of delphinid mixed-species groups, we compared the number of individuals, the age composition, and the behaviour of single- and mixed-species sightings of Australian humpback (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) observed around the North West Cape, Western Australia. We found no difference in the number of individuals or the age composition of humpback dolphins present in single- and mixed-species sightings, whereas bottlenose dolphins were present in larger numbers in single-species sightings than in mixed-species sightings due to a higher number of adults. Socialising was the initial observed behavioural state of 36.1% of mixed-species sightings, compared to only 5.1% and 10.3% of humpback and bottlenose dolphin single-species sightings, respectively. Furthermore, both species travelled and foraged less frequently when in mixed-species groups. Of 93 mixed-species groups observed during a focal follow of ≥ 10 min, 32 (34.4%) involved aggressive and/or sexual behaviours typically initiated by bottlenose dolphins towards humpback dolphins while the remaining 61 (65.6%) involved only neutral and affiliative behaviours. The results of this study suggest that the observed mixed-species groups provide multiple social benefits, particularly those pertaining to socio-sexual behaviours and the development and care of young.Significance statementNumerous species of dolphin are known to form mixed-species groups. Few studies have, however, investigated the antipredator, foraging, and/or social benefits that these species may gain by grouping with other species. Investigating these benefits is key to understanding the impacts of mixed-species groups on the species and individuals involved. We evaluated the potential functions of mixed-species groups of two sympatric, inshore dolphin species — the Australian humpback dolphin and the Indo-Pacific bottlenose dolphin. We found that both species engage in socialising behaviour more frequently when in mixed-species groups and that they engage in a diverse variety of interspecific behavioural interactions. Our results not only indicate that social benefits are the key drivers of these mixed-species groups, but they also highlight the complexity of social interactions between dolphin species.

Foraging preferences of an apex marine predator revealed through stomach content and stable isotope analyses

Insights into the food habits of predators are essential for maintaining healthy predator populations and the functioning of ecosystems. Stomach content and stable isotope analyses were used to investigate the foraging habits of an apex predator, the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in south-western Australia. A total of 2,594 prey items from 26 families were identified from the stomachs of 10 deceased stranded dolphins. Fish otoliths from stomach contents were used to identify fish to family or species level. Ninety-three percent of identified stomach contents were perciforme fishes, however, perciformes comprised only 30% of the catch during prey sampling. Gobiidae species, small fish generally <100 mm in total length, were the most prevalent family identified in dolphin stomachs, accounting for 82% of identified prey, yet Gobiidae accounted for 12.7% of the catch during prey sampling. For stable isotope analyses, tissue samples from 14 free-ranging dolphins were analyzed for nitrogen (δ15N) and carbon (δ13C) ratios. From stable isotope analyses and boat-based dolphin photo-identification surveys (n = 339, 2007–2011), results indicated niche differentiation between coastal and inshore (bay and estuarine habitat) dolphins. Carbon signatures showed that coastal dolphins had a more pelagic diet compared to a benthic diet observed in the inshore dolphins. Whereas, nitrogen signatures of inshore dolphins showed higher nitrogen levels than coastal dolphins, likely attributed to feeding on enriched prey typical of estuarian environments. Overall, these results indicated that bottlenose dolphins in the study area were selective foragers and that their foraging is specialized by the habitats most frequently used.

Vulnerability of threatened Australian humpback dolphins to flooding and port development within the southern Great Barrier Reef coastal region

In this study, we used a 10-year (2007–2016) mark-recapture dataset to investigate the potential effects of flooding and port development on the population dynamics of Australian humpback dolphins (Sousa sahulensis), inhabiting the Fitzroy River and Port Curtis, within the southern Great Barrier Reef region. A Multisite Capture-Recapture model was used to quantify population size and demographic parameters for both sexes and sites. Flood occurrence and intensity (both sites), and port development (Port Curtis) were included as explanatory variables. Abundance estimates indicated that about 77 adult dolphins were present in both sites, of which 69% were females. Most females (69%) were resident with a yearly recruitment close to zero for most years. Most males and unsexed (68%) individuals showed little evidence of long-term residency. The abundances of males and unsexed individuals varied between 15 and 20 dolphins in the Fitzroy River and 19–26 in Port Curtis, but the accuracy was too low to assess changes. Female abundances started at 56 in both sites and declined to about 32 per site in 2011, coinciding with port development construction activities and a concurrent major flood. In Port Curtis, the number of females returned to their original levels once the port development was completed in 2013. In the Fitzroy River, the declining trend continued and reached the lowest estimated abundance of 29 in 2016. As port developments and floods are expected to increase along the Queensland coastal region over coming decades, the results of this study highlight increasing concerns about the vulnerability and long-term sustainability of inshore dolphins in the GBR.

Dolphins and Boats: When Is a Disturbance, Disturbing?

Globally, exploitation of marine mammals has shifted from hunting to viewing over the last few decades. While refraining from actively killing animals may have a positive effect on marine mammal populations, whale and dolphin watching can induce changes such as displacement from preferred habitat and disruption of foraging that may also have severe fitness costs. Under some circumstances, this non-lethal disturbance may affect populations in a manner similar to directed mortality. Here, we focus on inshore dolphin populations that are known to show short-term behavioural responses to boat approaches. Long-term fitness effects have only been clearly identified in a small number of these populations, and all share certain characteristics, i.e. closed, small and food limited. This raises the question of importance of context when considering the long-term effects of disturbance, since many dolphin populations may be open, large, and/or free from resource restriction. We explored the effect of disturbance based on the characteristics of populations using the population consequences of disturbance (PCoD) framework. PCoD was developed to link short-term changes in individual behaviour and physiology to presumed long-term effects on population dynamics. To ensure our scenarios were biologically plausible, they reflected the ecological context of four well-studied populations of dolphins, Doubtful Sound NZ, Sarasota Bay USA, Durban Bay SA and Jervis Bay AUS, in terms of their size, closure and food resources. We found that the characteristics of the populations being disturbed are important with regards to the level of disturbance that could be tolerated. Closed populations were most sensitive, while large, open populations with no food limitation appeared to be able to withstand a higher probability of disturbance. This implies that population characteristics should be accounted for when determining the suitability of whale and dolphin watching operations in a given area.

Long-term trends and a risk analysis of cetacean entanglements and bycatch in fisheries gear in Australian waters

Assessments of fisheries interactions with non-target species are crucial for quantifying anthropogenic threatening processes and informing management action. We perform the first multi-jurisdictional analysis of spatial and temporal trends, data gaps and risk assessment of cetacean interactions with fisheries gear for the entire Australian Exclusive Economic Zone. Bycatch and entanglement records dating from 1887 to 2016 were collected from across Australia (n = 1987). Since 2000 there has been a substantial increase in reported bycatch and entanglements and this is likely the result of improved monitoring or recording by some jurisdictions and fisheries as well as changing fishing effort, combined with continuing recovery of baleen whale populations after cessation of commercial whaling. A minimum of 27 cetacean species were recorded entangled, with over 30% of records involving interactions with threatened, vulnerable or endangered species. Three times the number of dolphins and toothed whales were recorded entangled compared to baleen whales. Inshore dolphins were assessed as most vulnerable to population decline as a result of entanglements, though humpback whales, common bottlenose dolphins, and short-beaked common dolphins were the most frequently caught. Only one-quarter of animals were reported to have survived entanglement, either through intervention or self-release from fishing gear. Spatial mapping of the records highlighted entanglement hotspots along the east and west coast of the continent, regions where high human population density, high fishing effort, and high density of migrating humpback whales all occur, augmented by high captures of dolphins in shark control gear along the east coast. Areas of few entanglements were more remote, highlighting substantial bias in entanglement reporting. Our gap analysis identified discrepancies in data quality and recording consistency both within and between jurisdictions. Disparities in the types of fisheries data provided for the analysis by different state agencies limited our ability to compile bycatch data in a representative and systematic way. This research highlights the need for improved standardised data recording and reporting by all agencies, and compulsory sharing of detailed fisheries interaction and effort data, as this would increase the value of entanglement and bycatch data as a conservation and management tool.

Shark bite injuries on three inshore dolphin species in tropical northwestern Australia

AbstractPredation risk has a profound influence on the behavior of marine mammals, affecting grouping patterns and habitat use. Dolphins frequently bear evidence of shark bites, which can provide an indirect measure of predation pressure. Using photo‐identification data, we investigated the prevalence of shark bites on three sympatric species of inshore dolphin, the Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo‐Pacific bottlenose dolphin (Tursiops aduncus), among four study sites in northwestern Australia. Bite prevalence varied markedly between species, with 72% of snubfin, 46% of humpback, and 18% of bottlenose dolphins exhibiting evidence of shark bites. Binomial logistic regression confirmed a high likelihood of bite presence on snubfin dolphins, and at one particular site for snubfin and bottlenose dolphins. The prevalence of tiger shark (Galeocerdo cuvier) bites on snubfin dolphins was high, and bites attributed to other carcharhinid sharks were observed on all species. While acknowledging methodological differences with other studies, the prevalence of shark bites on snubfin dolphins is among the highest reported for any dolphins, suggesting predation risk represents an important but varying influence thereon. This study provides a baseline for future investigations into the affect of predation risk on the behavioral ecology of these sympatric species.

Site-Specific Assessments of the Abundance of Three Inshore Dolphin Species to Inform Conservation and Management

Assessing the abundance of wildlife populations is essential to their effective conservation and management. Concerns have been raised over the vulnerability of tropical inshore dolphins in waters off northern Australia to anthropogenic impacts on local populations, yet a lack of abundance data precludes assessment of their conservation status and the management of threats. Using small vessels as cost-effective research platforms, photo-identification surveys and capture-recapture models were applied to provide the first quantitative abundance data for Australian snubfin (Orcaella heinsohni), Australian humpback (Sousa sahulensis), and Indo-Pacific bottlenose dolphins (Tursiops aduncus) at five sites in the Kimberley region of north-western Australia. The abundance of each species was highly variable between different sites, likely reflecting species-specific habitat preferences. Within the c. 130 km2 study sites, the estimated abundance of most species was ≤ 60 individuals (excluding calves), and fewer than 20 humpback dolphins were identified at each site in any one 3-5 week sampling period. However, larger estimates of c. 130 snubfin and c. 160 bottlenose dolphins were obtained at two different sites. Several local populations showed evidence of site fidelity, particularly snubfin dolphins. By implementing a standardized, multi-site approach, data on local populations were provided within a broader, regional context, and indicated that each species is patchily distributed in the region. This highlights the need for site-specific baseline data collection using appropriate survey techniques to quantitatively assess the potential impacts of threatening activities to local populations. These findings further illustrate the need to gain a greater understanding of known and potential threats to inshore dolphin populations, their relative impacts, and to mitigate where necessary. In particular, the level of interactions with inshore gillnet fisheries requires urgent assessment. An ideal candidate site for a long-term study of snubfin dolphin population dynamics is identified, where trends in abundance and their influencing factors could be investigated. The methods employed herein provide an example of rigorous, site-specific population assessments of inshore dolphins that are broadly applicable to such studies elsewhere.

Humpback Dolphins of Western Australia: A Review of Current Knowledge and Recommendations for Future Management.

Among the many cetacean species that occupy Australian coastal waters, Australian humpback dolphins, Sousa sahulensis, are one of the most vulnerable to extirpation due to human activities. This review summarises the existing knowledge, presently occurring and planned research projects, and current conservation measures for humpback dolphins in Western Australia (WA). Rapid and wide-scale coastal development along the northern WA coastline has occurred despite a lack of baseline data for inshore dolphins and, therefore, without a precautionary approach to their conservation. The distribution, abundance, habitat use, and population structure of humpback dolphins remain poorly understood. Less than 1% of their inferred distribution has so far been studied to understand local population demography. The sparse data available suggest that WA humpback dolphins occur as localised populations in low numbers within a range of inshore habitats, including both clear and turbid coastal waters. Marine protected areas cover a third of their inferred distribution in WA, but the efficacy of these reserves in protecting local cetacean populations is unknown. There is a pressing need for coordination and collaboration among scientists, government agencies, industry bodies, Traditional Owners, and local community groups to fill in the gaps of information on humpback dolphins in WA. The recently developed strategies and sampling guidelines developed by state and federal governments should serve as a best practise standard for collection of data aimed at assessing the conservation status of humpback dolphins in WA and Australia.

Epidemiology of lobomycosis-like disease in bottlenose dolphins Tursiops spp. from South America and southern Africa

We report on the epidemiology of lobomycosis-like disease (LLD), a cutaneous disorder evoking lobomycosis, in 658 common bottlenose dolphins Tursiops truncatus from South America and 94 Indo-Pacific bottlenose dolphins T. aduncus from southern Africa. Photographs and stranding records of 387 inshore residents, 60 inshore non-residents and 305 specimens of undetermined origin (inshore and offshore) were examined for the presence of LLD lesions from 2004 to 2015. Seventeen residents, 3 non-residents and 1 inshore dolphin of unknown residence status were positive. LLD lesions appeared as single or multiple, light grey to whitish nodules and plaques that may ulcerate and increase in size over time. Among resident dolphins, prevalence varied significantly among 4 communities, being low in Posorja (2.35%, n = 85), Ecuador, and high in Salinas, Ecuador (16.7%, n = 18), and Laguna, Brazil (14.3%, n = 42). LLD prevalence increased in 36 T. truncatus from Laguna from 5.6% in 2007-2009 to 13.9% in 2013-2014, albeit not significantly. The disease has persisted for years in dolphins from Mayotte, Laguna, Salinas, the Sanquianga National Park and Bahía Málaga (Colombia) but vanished from the Tramandaí Estuary and the Mampituba River (Brazil). The geographical range of LLD has expanded in Brazil, South Africa and Ecuador, in areas that have been regularly surveyed for 10 to 35 yr. Two of the 21 LLD-affected dolphins were found dead with extensive lesions in southern Brazil, and 2 others disappeared, and presumably died, in Ecuador. These observations stress the need for targeted epidemiological, histological and molecular studies of LLD in dolphins, especially in the Southern Hemisphere.

Observations on Australian Humpback Dolphins (Sousa sahulensis) in Waters of the Pacific Islands and New Guinea.

The Australian humpback dolphin, Sousa sahulensis, has recently been described to occur in northern Australian coastal waters. However, its distribution in adjacent waters of the Pacific Islands and New Guinea remains largely unknown. Although there have been few studies conducted on inshore dolphins in these regions, the available information records humpback dolphins primarily from the Kikori Delta in Papua New Guinea, and Bird's Head Seascape in West Papua. Research in southern Papua New Guinea indicates that humpback dolphins are indeed S. sahulensis, based on cranial and external morphometrics, external colouration and the preliminary genetic analysis presented here. A similar situation exists for the Australian snubfin dolphin, Orcaella heinsohni, where it is assumed that the species also occurs along the Sahul Shelf coastal waters of northern Australia and New Guinea. There are anecdotal reports of direct catch of Australian humpback dolphins for use as shark bait, coastal development is increasing, and anthropogenic impacts will continue to escalate as human populations expand into previously uninhabited regions. Future research and management priorities for the Governments of the Pacific Islands and Indonesia will need to focus on inshore dolphins in known regional hotspots, as current bycatch levels appear unsustainable.

Mortality of inshore marine mammals in eastern Australia is predicted by freshwater discharge and air temperature.

Understanding environmental and climatic drivers of natural mortality of marine mammals is critical for managing populations effectively and for predicting responses to climate change. Here we use a 17-year dataset to demonstrate a clear relationship between environmental forcing and natural mortality of inshore marine mammals across a subtropical-tropical coastline spanning a latitudinal gradient of 13° (>2000 km of coastline). Peak mortality of inshore dolphins and dugongs followed sustained periods of elevated freshwater discharge (9 months) and low air temperature (3 months). At a regional scale, these results translated into a strong relationship between annual mortality and an index of El Niño-Southern Oscillation. The number of cyclones crossing the coastline had a comparatively weak effect on inshore marine mammal mortality, and only in the tropics. Natural mortality of offshore/migratory cetaceans was not predicted by freshwater discharge, but was related to lagged air temperature. These results represent the first quantitative link between environmental forcing and marine mammal mortality in the tropics, and form the basis of a predictive tool for managers to prepare responses to periods of elevated marine mammal mortality.

Tropical inshore dolphins of north-western Australia: Unknown populations in a rapidly changing region.

Australian Snubfin Orcaella heinsohni, Indo-Pacific Humpback Sousa chinensis and Indo-Pacific Bottlenose Dolphins Tursiops aduncus inhabit Australia’s tropical north-western coastline, a region undergoing extensive port development associated with the massive expansion of the oil, gas and mining industries. The current lack of data on dolphin population sizes or trends precludes impact assessments of developments on these protected species. Furthermore, the Western Australian and Commonwealth Government conservation listings of tropical inshore dolphins do not reflect their international listings. From April to July, 2010, we conducted ad hoc boat-based surveys (n=55) of inshore delphinids at seven sites across north-western Australia from Coral Bay in the south (23.1°S: 113.8°E) to Cable Beach in the north (17.9°S: 122.2°E). We documented the locations of these three species from which we obtained photoidentification and biopsy data, as well as reports of Australian Snubfin Dolphin sightings from researchers and community groups. The data from this limited field effort confirm that Indo-Pacific Humpback and Indo-Pacific Bottlenose Dolphins occur in the waters adjacent to each north-western Australian urban centre and show that the range of the Australian Snubfin Dolphin extends considerably further south-west than previously reported. Given the scale of coastal developments and the vulnerability of isolated cetacean populations to fragmentation or extirpation, assessments of the viability of dolphin populations are required. Our data suggest that the Australian Snubfin, Indo-Pacific Humpback and Indo-Pacific Bottlenose Dolphins need to be considered as likely to be impacted by coastal developments across north-western Australia.

Natal philopatry, ranging behavior, and habitat selection of juvenile bottlenose dolphins in Sarasota Bay, Florida

Movement patterns and habitat selection are influenced by factors such as resource availability, predation risk, and social interactions, and the relative importance of each of these variables can change over an animal’s life span. Although ranging patterns and habitat use of adult dolphins have been explored in some areas, relatively little is known about how these behaviors develop as young dolphins mature. This study explored natal philopatry during the juvenile period and behavioral development of ranging and habitat-use patterns in newly independent bottlenose dolphins (Tursiops truncatus) at a long-term study site in Sarasota Bay, Florida. To achieve this we used both long-term sighting data from the resident dolphin community in Sarasota Bay and new information on movements, habitat selection, and social associations collected through boat-based focalanimal behavioral observations on 27 individually identifiable juveniles during 2005–2008. We documented differences in ranging patterns and habitat use of juvenile dolphins by sex, season, and age, and investigated the degree of maternal influence on these behaviors and the functional significance of juvenile groups. We found that male and female dolphins in Sarasota Bay had similar ranging and habitat-selection patterns during the juvenile period. Both sexes exhibited a high degree of philopatry to natal areas as juveniles, with dispersal occurring only rarely by members of either sex. Seasonal and age-related differences in juvenile behavior were evident, and lasting maternal influences on habitat selection and ranging patterns postindependence are apparent. These findings provide some of the 1st information on juvenile marine mammal behavior that contributes to our understanding of resident inshore dolphin behavior throughout the life history and are potentially important to management and conservation efforts.

Using calls to estimate the abundance of inshore dolphins: a case study with Pacific humpback dolphins Sousa chinensis

1 Assessing the number of animals in a population is a fundamental requirement for effective wildlife management. Determining this information for cetaceans can be logistically difficult, and the abundance of inshore cetaceans along most of the world's coastline is unknown. 2 In this study we illustrate the potential of using sound as a tool for estimating the abundance of inshore cetaceans, using Pacific humpback dolphins Sousa chinensis . 3 Acoustic recordings of humpback dolphins were made in conjunction with visual observations of school size from a land-based platform on Stradbroke Island, Australia. 4 The mean number of calls recorded per 3-min sample period was regressed against the number of dolphins observed using schools for which more than three sample periods were recorded. The relationship estimated number of dolphins = 2·39 × the mean number of calls per 3-min sample was used to estimate the number of dolphins in schools for which fewer than four samples were recorded. Comparing these results against known group sizes indicated that this estimation technique is acceptable. 5 Recordings could be made using remotely deployed hydrophone units or submerged autonomous units to provide information on the occurrence and group size of inshore delphinids within an area. 6 Inexperienced personnel could deploy and retrieve recording units. Analysis would require training to recognize sound types from different species, or computer-based sound recognition programs. 7 We conclude that simple techniques using phonations can provide estimates of relative abundance for one species of inshore cetacean. The technique is acceptable for groups of fewer than nine individuals and should be developed to assess its usefulness for studying other species.

PROFILE: Marine Protected Areas and Dugong Conservation Along Australia's Indian Ocean Coast

/ The coastal zone of the Indian Ocean is coming under increasing pressure from human activities. Australia may be one of the few countries in this region that can afford to take adequate conservation measures in the near future. As it also has one of the longest Indian Ocean coastlines, Australia has the opportunity, and responsibility, to make a meaningful contribution to the conservation of Indian Ocean biodiversity. Threatened species, including marine turtles, inshore dolphins, and dugongs are an important component of that biodiversity. The dugong has been exterminated from several areas in the Indian Ocean, and it appears to be particularly threatened by mesh netting andhunting. Its long-term survival may depend on adequate protection in Australia, which contains the largest known Indian Ocean populations. This protection will require, in part, an appropriate system of marine protected areas (MPAs). This paper examines the adequacy of MPAs along Australia's Indian Ocean coast. Dugongs occur in two MPAs in Western Australia. The proposed expansion of the system of marine reserves is based primarily on representative samples of ecosystems from each biogeographic region. It is inadequate because it does not take into account the distribution and relative abundance of threatened species. If the conservation of biodiversity is to be maximized, the system of MPAs should incorporate both representativeness and the needs of threatened species. The level of protection provided by MPAs in Western Australia is low. Under current government policy potentially damaging activities, including commercial fishing, seismic surveys, and oil and gas drilling are permitted in protected areas.KEY WORDS: Marine protected areas; Dugongs; Western Australia; Indian Ocean; Conservation; Biodiversity

Interspecific differences in whistles produced by inshore dolphins in Moreton Bay, Queensland, Australia

The sounds produced by bottlenose dolphins, Tursiops truncatus, and Indo-Pacific humpback dolphins, Sousa chinensis, were recorded on 11 days from 3 April to 13 August 1990 in Moreton Bay, eastern Australia. Twelve hours and 34 minutes of sound were recorded. The physical structure of whistles was described using a variable for duration and seven variables for frequency. Data were subjected to principal components analysis (PCA) and canonical discriminant analysis (CDA). PCA demonstrated the range of whistle contours recorded. CDA demonstrated differences in the whistles between species. Humpback dolphin whistles differed in shape (frequency modulation) and were generally of shorter duration and higher overall frequency than those of bottlenose dolphin whistles.

Differentiation between Inshore and Offshore Spotted Dolphins in the Eastern Tropical Pacific Ocean

Multivariate analyses were performed on 36 morphometric and meristic skull measurements taken on 613 spotted dolphins ( Stenella attenuata ) from the eastern tropical Pacific Ocean. Corrections were made to account for sexual dimorphism. Findings extend previous results which indicate sharp demarcation between two stocks: a larger, more robust coastal or inshore form; and a smaller, more terete pelagic or offshore stock. Sample means from 5° latitude-longitude blocks were projected onto principal component I and showed separation of four inshore from 19 offshore blocks, primarily on the basis of size involving most morphometric characters. A second component with high loadings on tooth counts summarized differences of three southern inshore blocks (adjacent to Central America) from a fourth, more northerly block located at the Gulf of California. Cluster analyses provided a similar summary of interblock associations. Principal components and cluster analysis based on individual specimens were also used to identify seven individuals with questionable affinity. The remaining 606 specimens (575 offshore, 31 inshore) were used to generate a discriminant axis and associated classification functions that correctly allocated all specimens. The best character for distinguishing between offshore and inshore specimens is Tooth Width. Classificatory information is provided to enable other researchers to assign unknown specimens.

Social Organisation of Inshore Dolphins (Tursiops aduncus and sousa) in the Indian Ocean

Social Organisation of Inshore Dolphins (Tursiops aduncus and sousa) in the Indian Ocean