Dolphin Species Research Articles

Dolphin whistles can be useful tools in identifying units of conservation

BackgroundPrioritizing groupings of organisms or ‘units’ below the species level is a critical issue for conservation purposes. Several techniques encompassing different time-frames, from genetics to ecological markers, have been considered to evaluate existing biological diversity at a sufficient temporal resolution to define conservation units. Given that acoustic signals are expressions of phenotypic diversity, their analysis may provide crucial information on current differentiation patterns within species. Here, we tested whether differences previously delineated within dolphin species based on i) geographic isolation, ii) genetics regardless isolation, and iii) habitat, regardless isolation and genetics, can be detected through acoustic monitoring. Recordings collected from 104 acoustic encounters of Stenella coeruleoalba, Delphinus delphis and Tursiops truncatus in the Azores, Canary Islands, the Alboran Sea and the Western Mediterranean basin between 1996 and 2012 were analyzed. The acoustic structure of communication signals was evaluated by analyzing parameters of whistles in relation to the known genetic and habitat-driven population structure.ResultsRecordings from the Atlantic and Mediterranean were accurately assigned to their respective basins of origin through Discriminant Function Analysis, with a minimum 83.8% and a maximum 93.8% classification rate. A parallel pattern between divergence in acoustic features and in the genetic and ecological traits within the basins was highlighted through Random Forest analysis. Although it is not yet possible to establish a causal link between each driver and acoustic differences between basins, we showed that signal variation reflects fine-scale diversity and may be used as a proxy for recognizing discrete units.ConclusionWe recommend that acoustic analysis be included in assessments of delphinid population structure, together with genetics and ecological tracer analysis. This cost-efficient non-invasive method can be applied to uncover distinctiveness and local adaptation in other wide-ranging marine species.

Cetaceans Sightings During Research Cruises in Three Remote Atlantic British Overseas Territories

Marine mammal sightings were recorded during research cruises to three remote, mid-ocean British Overseas Territories in the South Atlantic and Southern Ocean. In March to April 2018 and 2019, the Exclusive Economic Zones (EEZs) of tropical St Helena and temperate Tristan da Cunha were surveyed. The sub-polar waters of South Georgia and the South Sandwich Islands (SGSSI) were surveyed in February to March 2019. At St Helena in 2018, five species were recorded during 11 sightings, and in 2019, four species, with one additional unidentified species, during seven sightings. Most of these sightings were of dolphin species, which are known to be resident around the Island and seamounts. In Tristan da Cunha in 2018, a total of five identified and one unidentified species were recorded during six sightings, half of which were associated with the Islands or seamounts. In 2019, due to rough weather, no sightings were recorded in the Tristan da Cunha waters. Around SGSSI, 162 sightings of 236 cetaceans were made in 2019, mostly of baleen whales, with seven species identified with certainty. Sightings around the southern South Sandwich Islands included beaked whales and large dolphins, whereas baleen whales dominated in the northern South Sandwich Islands. These results provide new data for rarely surveyed regions, helping to build a spatial picture of important areas for marine mammals, which will help inform marine spatial protection strategies.

Impact of Salinity Changes in Shatt Al-Arab Estuary on Biodiversity of Marine Mammals of the Arabian Gulf: A Review

Salinity changes in the Shatt Al-Arab Estuary and North-West Arabian Gulf were monitored and reviewed in terms of the shortage of freshwater inflows to the Shatt Al-Arab Estuary. Data from previous and current surveys on marine mammals in the area have also been checked and compared to study the biodiversity under newly-developed circumstances. The Eco-physiological investigation was performed to assess the salinity tolerance limits of whales, dolphins and dugong. One-third of the world’s 81 species of whales and dolphins, collectively called cetaceans, are thought to occur off the shores in the area. The new checklist is prepared according to recent surveys in the neighbouring Arab Gulf countries and the known checklist of mammals in Iraqi waters. Spatial variation of the marine mammals of the southern part was governed by the occurrence of feeding habitats rather than a direct response to salinity variations. Alteration of seaweed’s habitats in response to water pollution is reported to have a direct effect on the biodiversity of mammals in the gulf. The results of this review were discussed in terms of salinity tolerance, hazardous ecological factors and spatial variation. No obvious effect of salinity changes imposed by the shortage of freshwater inflow on the distribution or loss of marine mammals neither on their habitat in the Arabian Gulf.

Acoustic deterrent devices as mitigation tool to prevent dolphin-fishery interactions in the Aeolian Archipelago (Southern Tyrrhenian Sea, Italy)

In this study, acoustic deterrent devices (Pingers) have been tested to reduce dolphin-fishery interaction in the Aeolian Archipelago (Southern Italy), where ecosystem degradation and overfishing have increasingly brought bottlenose dolphin ( Tursiops truncatus ) and striped dolphin ( Stenella coeruleoalba ) into conflict with local artisanal fishery. Thirty-six trials with FishTek banana Pingers have been performed between April and September 2017 on Spicara maena gillnet, trammel net, “Lampara” net, and hand-operated squid jig line (“Totanara”). A conspicuous decrease in depredation-related damages was recorded on S. maena gillnet (100 %) and Lampara net (86 %) tests, corresponding to a great increase in catch weight (Kg) and profit (€). On the contrary, in squid hand-jig lines, the depredation events were high (60 %) and a dramatic decrease of catch and profit was recorded. No significative differences in weight and profit and any dolphin-related damages have been observed between test and control trammel nets, but fish species included in dolphin diet were more abundant in test than in control nets. Our results suggested that different factors, such as dolphin species, season, habitat and fish species distribution, may affect the efficacy of Pingers. Furthermore, discard represent about 49 % of total catch and include potentially valuable bycaught (namely non-target) fish species, such as Sparisoma cretense , highly abundant in the area but poorly evaluated on the local market. Pingers and inclusion of non-target species in the local market represent potential mitigation tools to reduce the conflict, but they need adequate planning.

Publisher’s Note to Launch Hydrobiology

When I was a student at Wuhan University, the last captive individual of baiji (Lipotes vexillifer), a species of freshwater dolphin, was living at the Freshwater Dolphin Research Centre of Wuhan Institute of Hydrobiology, Chinese Academy of Sciences [...]

Reviews: Komodo National Park as a conservation area for the komodo species (Varanus komodoensis) and sustainable tourism (ecotourism)

Abstract. Hidyarko AIF, Gayatri AC, Rifa VA, Astuti A, Kusumaningrum L, Mau YS, Rudiharto H, Setyawan AD. 2021. Komodo National Park as a conservation area for the komodo species (Varanus komodoensis) and sustainable ecotourism. Intl J Trop Drylands 5: 27-40. Komodo National Park (East Nusa Tenggara Province, Indonesia) is a biodiversity conservation area with the main aim to protect the original habitat and remaining population of Komodo dragon species (Varanus komodoensis Ouwens, 1912). Nonetheless, the area also has great potential as one of the objects of tourist attraction. The purpose of this study is to see the sustainable function of conservation and tourism in Komodo National Park. Komodo National Park covers land area of more than 603 square kilometers and 1214 square kilometers of marine habitat. The land habitats have 277 species of animals while the marine habitats have 253 species of corals, more than 1,000 species of fish, and 25 species of whales and dolphins. One of the main attractions of the Komodo National Park area is the ancient giant reptile of the Komodo dragon (Varanus komodoensis). The tourism management of Komodo National Park (KNP) is currently done through an ecotourism approach. The tourism zone is determined based on part of the Komodo National Park which has the potential for land and marine tourism with a diversity of flora and fauna. The participation of communities living around KNP in the ecotourism business can increase local economics and conservation awareness; as well as their participation in conservation. Meanwhile, the factors that hinder community participation in tourism development are limited budget, apathy and low public awareness, fluctuations in tourist visits, and difficulties in marketing ecotourism products.

Predicting Cetacean Distributions in the Eastern North Atlantic to Support Marine Management

Data on species occurrence at the scale of their distributional range and the determination of their habitat use requirements are essential to support conservation and define management plans that account for their habitat requirements. For wide-ranging species, such as cetaceans, especially considering that their marine habitats include offshore areas, collection of such data is challenging. In the absence of dedicated surveys, alternative methodologies are needed, such as the use of data collected from platforms of opportunity and modelling techniques to predict distribution in unsurveyed areas. Using 6 years of cetacean occurrence data collected along cargo ship routes between the Iberian Peninsula, northwestern African coasts and the Macaronesian islands, we developed ecological niche models to assess habitat preferences and predict suitable habitats of the eight most frequently sighted cetacean taxa in the area. Explanatory variables used for model fitting included topographic, oceanographic, detectability, geographic and seasonal features. To provide a robust habitat characterisation, along with predictions of habitat suitability, making best use of occurrence datasets, we applied two modelling techniques, GAM and Maxent, which offer complementary strengths. Coastal areas provide important habitats for common and bottlenose dophins, while other dolphin species (spotted and striped dolphins) have a more oceanic distribution. The predicted niches of Cuvier’s beaked whale and minke whales are mainly in the high seas at northern latitudes. Suitable habitats for sperm whales and pilot whales are mostly in southern areas in continental slope regions. For all the species, models indicated that areas around seamount features offer suitable habitats, likely of high relevance in oligotrophic offshore waters. As such, dedicated survey effort in such areas would facilitate development and implementation of appropriate management plans, which are currently lacking. Our models offer an important contribution to baseline knowledge of cetacean distribution at basin-scale in the region and could support the definition of priority areas, monitoring plans, and conservation measures, essential to comply with the requirements of the EU Marine Strategy Framework Directive.

Comparative biogeography and the evolution of population structure for bottlenose and common dolphins in the Indian Ocean

AbstractAimIn the marine environment, where there are few physical boundaries to gene flow, there is often nevertheless intraspecific diversity with consequences for effective conservation and management. Here, we compare two closely related dolphin species with a shared distribution in the Indian Ocean (IO) to better understand the biogeographic drivers of their population structure.LocationGlobal oceans and seas with a focus on the Indian OceanTaxonTursiops sp. and Delphinus sp.MethodsBayesian, ordination, assignment, statistical and phylogenetic analyses to assess phylogeography, connectivity and population structure using microsatellite and mitochondrial DNA genetic markers.ResultsBoth Tursiops sp. and Delphinus sp. showed population structure across the western IO and, in each case, populations in the Arabian Sea (off India, Pakistan and Oman) were most differentiated. Comparisons with other populations worldwide revealed independent lineages in this geographic region for both genera. For T. aduncus, (for which multiple sites within the IO could be compared), Bayesian modelling best supported a scenario of expansion southwards following a bottleneck event resulting in differentiation between the northern and western IO. For Delphinus, the same pattern is even more pronounced. Populations in the Arabian Sea region of the north‐western IO show genetic isolation for each of the two genera, consistent with other studies of cetacean species in this region.Main conclusionsWe propose that changes in the intensity of the southwest monsoon during the climate cycles of the Pleistocene could have affected regional patterns of productivity and represent an important biogeographic driver promoting the observed patterns of differentiation and population dynamics seen in our focal species. Patterns of population genetic structure are consistent with phenotypic differences, suggesting an influence from distinct habitats and resources, and emphasising the need for effective conservation measures in this geographic region.

The biosonar of the boto: evidence of differences among species of river dolphins (Inia spp.) from the Amazon.

Echolocation clicks can reflect the anatomy of the vocalizing animal, enabling the distinction of species. River dolphins from the family Iniidae are formally represented by one species and two subspecies (Inia geoffrensis geoffrensis and I. g. humboldtiana). Additionally, two other species have been proposed (I. boliviensis and I. araguaiaensis) regarding its level of restricted distribution and morph-genetics differences. For the Committee on Taxonomy of the Society for Marine Mammalogy, the specific status of the proposed species relies on further knowledge on morphology, ecology, and genetics. Given that species-specific status is required for conservation efforts, we described and compared the echolocation clicks of Inia spp., searching for specific differences on their vocalizations. The sounds were captured with a Cetacean Research ™ C54XRS (+3/−20 dB, −185 dB re: 1V/μPa) in Guaviare River (Orinoco basin), Madeira River (Madeira basin), Xingu River (Amazon Basin), and Araguaia River (Tocantins-Araguaia basin). We found significant differences in all analyzed parameters (peak frequency, 3 dB bandwidth, 10 dB bandwidth and inter-click interval) for all species and subspecies. Differences in acoustical parameters of clicks are mainly related to the animal’s internal morphology, thus this study may potentially support with information for the species-level classification mostly of I. araguaiaensis (the Araguaian boto). Classifying the Araguaian boto separately from I. geoffrensis has important implications for the species in terms of conservation status, since it is restricted to a highly impacted river system.

Occurrence, distribution and composition of marine mammals in the bight of Bony, Nigeria

Information on the distribution, occurrence and population structure of cetaceans (whales and dolphins) of the Atlantic coast of Nigeria in West Africa remains fairly sparse to date, with few detailed studies being conducted on this valuable marine resource. This paper highlights the abundant cetacean community sighted in the Nigerian coastal waters and the respective importance of this area as a prime coastal habitat for these mammals. The secondary objective was the evaluation of this resource and development of appropriatemanagement policies. Opportunistic data was collected on board six different marine vessels belonging to some international oil companies (IOC) in Nigeria, whose primary objective was to conduct seismic operations. 8,327 hours and 36 minutes of effort was logged during 2 wet and 3 dry seasons respectively, covering almost 880 km2 at a depth range of 10 to 70 m. The total number of individuals recorded was 2199 of which 80% were dolphins and 20% were whales. Out of these, 55.14% was sighted at depth range of 21 – 30 m. This was followed by 30.42% recorded at depth range of 31 - 40 m. The least frequency of 0.75 % was recorded at depth range of 61- 70m. Five hundred and twenty-five (525) individual whales was recorded, out of which 77.14% were adults and 22.86% were juveniles, while 1674 individual dolphins were recorded with 52.63% juveniles and 47.37% adult. Four species of dolphins were identified. The bottlenose dolphins, Tursiops truncatus was the most abundant owing to the large size of the groups observed, followed by common dolphin, Delphinus delphis. All species of dolphins identified occurred throughout the sampling months. Two species of whales were identified with the humpback whale (Megaptera novaeangliae) predominant and killer whales (Orcinus orca) which seem to be present in just a part of a year. Nigerian coastal water is moderately rich in cetacean diversity, which is currently underreported due to limited research.Keywords: Whales, dolphins, species diversity, opportunistic surveys, Nigeria.

Autonomous towed hydrophone system detects many beaked whales and other cetacean species in waters of the Southern Ocean

A SoundTrap ST300HF hydrophone recorder in a streamlined, flooded towbody was towed behind expeditionary tourism vessels on trips to South Georgia and the South Sandwich Islands and to the Antarctic Peninsula in December 2019—February 2020. Recordings were analyzed to identify acoustic detections of cetacean species. Identified species included sperm whales (Physeter macrocephalus) and southern bottlenose whales (Hyperoodon planifrons). Acoustic detections also included echolocation pulses from several previously described beaked whale pulse types (BW37 and BW58) as well as a possibly new type of beaked whale echolocation pulse. Narrow-band high-frequency (NBHF) echolocation signals (typical of porpoises and some dolphin species) were detected at several locations, and one of these coincided with a sighting of hourglass dolphins (Lagenorhynchus cruciger). Unidentified large delphinids were also detected several times. This study shows the utility of a simple towed hydrophone system on a vessel of opportunity to study the distribution of cetaceans in rough seas that are difficult to study by visual survey methods. Additional research is needed to link the unidentified echolocation signals to known species throughout waters of the Southern Ocean.

Tourism informing conservation: The distribution of four dolphin species varies with calf presence and increases their vulnerability to vessel traffic in the four‐island region of Maui, Hawai‘i

Abstract We need reliable information about the spatial and temporal distribution of mobile species to effectively manage anthropogenic impacts to which they are exposed. Yet, we often cannot sustain dedicated annual surveys and data obtained from platforms of opportunity offer an alternative avenue to understand where these species spend time. Four odontocete species that occur in the four‐island region of Maui, Hawai'i, USA, are vulnerable to a range of human activities, but there is a lack of information regarding their distribution. We therefore do not know the extent of the risk these activities present for the conservation of these species (bottlenose dolphins, spinner dolphins, Pantropical spotted dolphins and false killer whales). We used a cross‐validated maximum entropy (MaxEnt) occupancy model to estimate the distribution of these four species in an area extensively observed from platforms of opportunity (PoP). We then determined in a similar fashion whether the calves of those species were more likely to be observed in particular areas and whether distribution changed with season. Maxent models relying on local environmental variables described dolphin observations well (AUC > 0.7). Their distribution differed for all species when calves were present, indicating that different environmental variables describe area use for schools with calves present. The number of sighting events of all species varied significantly with season. Bottlenose dolphins and false killer whales were more prevalent in winter, while spotted and spinner dolphins were more prevalent in summer. We show that an overlap in the distribution of dolphin schools with calves and vessel traffic in the region could result in collision and chronic stress risks. This suggests a need for specific regulations for mitigating anthropogenic influences, such as acoustic disturbance or chronic energetic disturbance from vessel traffic. This elevated risk associated with vessel traffic is likely of conservation concern in this region for the endangered population of false killer whales and for spinner dolphins.

Delays in Protecting a Small Endangered Cetacean: Lessons Learned for Science and Management

Hector’s dolphin is a small, endangered dolphin species found exclusively in the inshore coastal waters of New Zealand. We draw on 36 years of involvement in research on Hector’s dolphin, and its subspecies Māui dolphin, to provide an overview of the species’ conservation biology, and summarize the incremental progress towards sustainable management. We offer lessons learned at the interface between science and management. These lessons emphasize the importance of acting early, having clear management goals and ensuring that the area over which protection measures are applied is sufficiently large to be biologically relevant. High-quality information is vital, but gaining appropriate conservation outcomes depends also on social and political processes. We warn that compromise can have high biological costs and that representation on stakeholder groups is usually biased toward extractive users and short-term economic perspectives. In New Zealand, outcomes have depended closely on politics; the greatest gains have been made when relevant government ministers took a special interest. Scientists have crucial roles in every phase of this process. Each country and each species will present their own challenges and opportunities. We trust, however, that lessons learned from Hector’s dolphin conservation will be useful to researchers and managers elsewhere.

Whole genomes reveal multiple candidate genes and pathways involved in the immune response of dolphins to a highly infectious virus.

Wildlife species are challenged by various infectious diseases that act as important demographic drivers of populations and have become a great conservation concern particularly under growing environmental changes. The new era of whole genome sequencing provides new opportunities and avenues to explore the role of genetic variants in the plasticity of immune responses, particularly in non-model systems. Cetacean morbillivirus (CeMV) has emerged as a major viral threat to cetacean populations worldwide, contributing to the death of thousands of individuals of multiple dolphin and whale species. To understand the genomic basis of immune responses to CeMV, we generated and analysed whole genomes of 53 Indo-Pacific bottlenose dolphins (Tursiops aduncus) exposed to Australia's largest known CeMV-related mortality event that killed at least 50 dolphins from three different species. The genomic data set consisted of 10,168,981 SNPs anchored onto 23 chromosome-length scaffolds and 77 short scaffolds. Whole genome analysis indicated that levels of inbreeding in the dolphin population did not influence the outcome of an individual. Allele frequency estimates between survivors and nonsurvivors of the outbreak revealed 15,769 candidate SNPs, of which 689 were annotated to 295 protein coding genes. These included 50 genes with functions related to innate and adaptive immune responses, and cytokine signalling pathways and genes thought to be involved in immune responses to other morbilliviruses. Our study characterised genomic regions and pathways that may contribute to CeMV immune responses in dolphins. This represents a stride towards clarifying the complex interactions of the cetacean immune system and emphasises the value of whole genome data sets in understanding genetic elements that are essential for species conservation, including disease susceptibility and adaptation.

Fission-fusion dynamics of a pelagic delphinid in the arctic: the white-beaked dolphin (Lagenorhynchus albirostris).

Delphinids exhibit great variability in their social structures. It is therefore important to document lesser known species, in extreme changing habitats, to compare and contrast mechanisms driving sociality. Here, we describe the first long-term assessment of social structure of white-beaked dolphins (Lagenorhynchus albirostris) using a compiled version of SOCPROG 2.8 and an 11-year photo-identification dataset (2002-2013) collected from whale-watching vessels at 2 sites (Faxaflói and Skjálfandi bays) off Iceland. We identified a total of 487 dolphins which are suggested to be part of an open population as shown by the discovery curve obtained analyzing photo-id data. The social analyses were restricted to 35 adults which were sighted on ≥5 different days. The mean residency time of white-beaked dolphins in our 2 study areas was of 95 days (SE = 35.63; 95% CI: 23-171), with the "migration-full interchange" model best describing movements of dolphins in and out of our 2 study sites. Social differentiation in this population was high (Likelihood: S = 0.87, SE = 0.04; r = 0.31, SE = 0.03) indicating diverse, non-random social relationships. Temporal associations best fit the model of "casual acquaintances" against the standardized lagged association rates with the majority of white-beaked dolphin associations being short-term, but with a few long-term across years. Testing for preferred companionship, long-term associations are favored over short-term. In this study, associations among white-beaked dolphins are short-term but with desirably long-term associations fitting into a society with fission-fusion dynamics. This information expands the latitudinal range for which social structure has been described for oceanic dolphin species.

A new kentriodontid (Cetacea: Odontoceti) from the early to middle Miocene of the western North Pacific and a revision of kentriodontid phylogeny.

A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai sp. nov., is described from the upper lower to lowest middle Miocene Kadonosawa Formation in Ninohe City, Iwate Prefecture, northern Japan. The holotype of Kentriodon sugawarai sp. nov., consists of a partial skull with ear bones, mandibular fragments, and some postcranial bones. This new species shares five unique characters with other species of Kentriodon. In addition, the new species differs from other species of the genus in displaying a narrow width of the squamosal lateral to the exoccipital in posterior view, the dorsolateral edge of the opening of the ventral infraorbital foramen that is formed by the maxilla and the lacrimal or the jugal, and at least three anterior dorsal infraorbital foramina. Our phylogenetic analysis based on 393 characters for 103 Odontoceti taxa yielded a consensus tree showing all previously identified kentriodontids as a monophyletic group that comprises the sister group of the crown Dephinoidea, which in turn include Delphinidae, Phocoenidae and Monodontidae. Our analysis also indicates that the distinct innovation of the acoustic apparatus (i.e., 13 out of 29 derived characters are from tympanoperiotic) would have occurred in the ancestral lineage of the Delphinoidea (sensu lato) including the monophyletic Kentriodontidae during their initial evolution and diversification.

Potential distribution of Guiana dolphin (Sotalia guianensis): a coastal-estuarine and tropical habitat specialist

Abstract Ecological niche models (ENMs) predict where species can occur in accordance with environmental factors. Suitability maps are generated through models to identify habitats more or less adapted to the species. Published works on the distribution and habitat use of Guiana dolphin, Sotalia guianensis, are limited to fine spatial scales. Here, we aimed to predict the potential geographical distribution of Guiana dolphins through ENMs and generate a map of suitable habitats for the species. Data were collected between 1997 and 2015 in Brazil, French Guiana, and Colombia. The environmental data were obtained from MARSPEC database with a cell resolution of 10 × 10 km. For modeling, 99 of the 859 initial occurrence points of the species were considered after rarefaction. Seven environmental variables were selected through factorial analysis: bathymetry, distance to shore, bathymetric slope, sea surface salinity (minimum monthly and annual range), and sea surface temperature (mean annual and annual range). Results from five distinct algorithms were assembled to generate the distribution model. Our findings show potential areas in shallow platforms of the continental margin of South and Central America, including regions where the species has never been reported, such as the Pacific Ocean, the Gulf of California, the Gulf of Mexico, and the oceanic islands in the Caribbean Sea. The absence of Guiana dolphins in these regions may be due to geographical (linking of North and South America), physical (water temperature), and biological (competition, limited ability to dispersal) limiting factors. The models suggest that the presence of other species of coastal dolphin may be an important limiting factor for the Guiana dolphin at both extremes of its distribution. The Guiana dolphin is habitat specialist with a clinal potential geographic distribution concentrated in tropical and subtropical shallow and coastal waters of the continental shelf of the western Atlantic Ocean. This more restricted distribution than reported by IUCN and other studies suggests a cautionary approach to its conservation status due to limited dispersal abilities and high overlap with human activities.

A comparative analysis of the karyotypes of three dolphins - Tursiops truncatus Montagu, 1821, Tursiops australis Charlton-Robb et al., 2011, and Grampus griseus Cuvier, 1812.

The aim of this study is to produce G-banded karyotypes of three dolphin species, Tursiops truncatus Montagu, 1821, Tursiops australisCharlton-Robb et al., 2011, and Grampus griseus Cuvier, 1812, and to determine if any differences between the species can be observed. Monolayer skin cultures were established and processed for chromosome study by trypsin banding. The results indicate that the three species here investigated have the same diploid number (2n = 44) and very similar gross chromosome morphology, however G-banding allows distinction between each species. Chromosome 1 in G. griseus is significantly different from the other 2 species, and chromosome 2 in T. australis is subtly different from the other 2 species. This result is of potential significance in taxonomic studies, and can provide an unequivocal answer in the assessment of suspected hybrids between these species.

Looking Back to Move Forward: Lessons From Three Decades of Research and Management of Cetacean Tourism in New Zealand

Cetacean tourism in Aotearoa New Zealand is now over 30 years old and has experienced substantial growth in visitor numbers and operations. The industry is remarkably diverse, targeting several dolphin and whale species, and encompassing varied habitats in coastal waters, fiords and submarine canyons. The knowledge and experience collected over these past 30 years has both advanced the global understanding of cetacean tourism, and influenced scientific practices for its study and management. Here we review the approaches taken in quantifying the impact of cetacean tourism in New Zealand, and critically assess the efficacy of the research and management strategies adopted. We place particular focus on the Bay of Islands, Hauraki Gulf, Kaikoura, Akaroa and Fiordland, areas that include the oldest, and longest studied industries nationally. We propose a set of best research practices, expose the most notable knowledge gaps and identify emerging research questions. Drawing on perspectives from the natural and social sciences, we outline the key determinants of failure and success in protecting cetacean populations from the detrimental impact of tourism. We suggest four golden rules for future management efforts: (1) acknowledge cetacean tourism as a sub-lethal anthropogenic stressor to be managed with precaution, (2) apply integrated and adaptive site- and species-specific approaches, (3) fully conceptualize tourism within its broader social and ecological contexts, and (4) establish authentic collaborations and engagement with the local community. Lastly, we forecast upcoming challenges and opportunities for research and management of this industry in the context of global climate change. Despite New Zealand's early establishment of precautionary legislation and advanced tourism research and management approaches, we detected flaws in current schemes, and emphasize the need for more adaptive and comprehensive strategies. Cetacean tourism remains an ongoing challenge in New Zealand and globally.

Dietary plasticity of two coastal dolphin species in the Benguela upwelling ecosystem

Defining the trophic relationships of marine predators and their dietary preferences is essential in understanding their role and importance in ecosystems. Here we used stable isotope analysis of skin samples (δ15N values reflecting trophic level and δ13C values reflecting foraging habitat) to investigate resource partitioning and spatial differences of the feeding ecology of dusky dolphins Lagenorhynchus obscurus and Heaviside’s dolphins Cephalorhynchus heavisidii from 2 coastal study sites separated by 400 km along the coast of central (Walvis Bay) and southern (Lüderitz) Namibia in the Benguela upwelling ecosystem. Overall, isotopic niches of both predators were significantly different, indicating partitioning of resources and foraging habitats. Despite their smaller body size, Heaviside’s dolphins fed at a significantly higher trophic level than dusky dolphins. Stable isotope mixing models revealed that both species fed on high trophic level prey (i.e. large Merluccius spp., large Sufflogobius bibarbatus, and Trachurus t. capensis) at Walvis Bay. The diet of both dolphin species included smaller pelagic fish and squid at Lüderitz. Spatial differences highlight that Heaviside’s and dusky dolphins may exhibit dietary plasticity driven by prey availability, and that they likely form distinct population segments. Important prey for both dolphin species, specifically Merluccius spp. and T. t. capensis, are the main target of trawl fisheries in the Benguela upwelling ecosystem, highlighting potential resource overlap between dolphins and fisheries.