Cetacean morbillivirus in coastal Indo-Pacific bottlenose dolphins, Western Australia

Cetacean morbillivirus (CeMV) has caused several epizootics in multiple species of cetaceans globally and is an emerging disease among cetaceans in Australia. We detected CeMV in 2 stranded coastal Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Western Australia. Preliminary phylogenetic data suggest that this virus variant is divergent from known strains.

Acute fatal sarcocystosis hepatitis in an Indo-Pacific bottlenose dolphin (Tursiops aduncus) in Hong Kong

Unlike most species in the genus Sarcocystis, Sarcocystis canis has a broad intermediate host range. Its life cycle is incompletely known and most reports are from the USA. Here we report fatal hepatitis in a 4year old male Indo-Pacific bottlenose dolphin (Tursiops aduncus) from Hong Kong associated with a S. canis-like infection. Diagnosis was made based on clinical presentation, histopathology, transmission electron microscopy (TEM), and molecular characterization. Microscopically, S. canis-like like infection was confined to the liver. Immature and mature schizonts were found in hepatocytes and the parasite was associated with generalized hepatic necrosis. By TEM, schizonts divided by endopolygeny, and merozoites lacked rhoptries. Molecular characterization of parasites present in liver and brain tissues at the cox1 gene showed a high degree of identity (97-98%) and clustered together with Sarcocystis canis, S. lutrae, S. arctica, S. speeri, S. turdusi, and S. rileyi in a phylogenetic study. This is the first report of S. canis-like infection from Asia.

Contrasted accumulation patterns of persistent organic pollutants and mercury in sympatric tropical dolphins from the south-western Indian Ocean

Due to their high trophic position and long life span, small cetaceans are considered as suitable bioindicators to monitor the presence of contaminants in marine ecosystems. Here, we document the contamination with persistent organic pollutants (POPs) and total mercury (T-Hg) of spinner (Stenella longirostris, n =21) and Indo-Pacific bottlenose dolphins (Tursiops aduncus, n=32) sampled from the coastal waters of La Réunion (south-western Indian Ocean). In addition, seven co-occurring teleost fish species were sampled and analyzed as well. Blubber samples from living dolphins and muscle from teleosts were analyzed for polychlorinated biphenyls (PCBs), DDT and metabolites (DDTs), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and polybrominated diphenyl ethers (PBDEs). Methoxylated PBDEs (MeO-PBDEs), reported as having a natural origin, were also analyzed. T-Hg levels were measured in blubber and skin biopsies of the two dolphin species. Stable isotopes δ(13)C and δ(15)N values were determined in skin of the dolphins and in the muscle of teleosts. For PCBs, HCHs and T-Hg, concentrations were significantly higher in T. aduncus than in S. longirostris. For other POP levels, intra-species variability was high. MeO-PBDEs were the dominant compounds (55% of the total POPs) in S. longirostris, while PCBs dominated (50% contribution) in T. aduncus. Other contaminants showed similar profiles between the two species. Given the different patterns of POPs and T-Hg contamination and the δ(15)N values observed among analyzed teleosts, dietary and foraging habitat preferences most likely explain the contrasted contaminant profiles observed in the two dolphin species. Levels of each class of contaminants were significantly higher in males than females. Despite their spatial and temporal overlap in the waters of La Réunion, S. longirostris and T. aduncus are differently exposed to contaminant accumulation.

Lethal fishing hook penetration and line entanglement in an adult bottlenose dolphin (Tursiops aduncus)

The carcass of a 15-year-old female Bottlenose dolphin (Tursiops aduncus) was retrieved from the Port River near Adelaide, South Australia, Australia. The animal was emaciated with five thick nylon fishing lines emerging from the oropharynx attached to a tangle of nylon and monofilament fishing line that also contained wire and eight fishing hooks. The mouth had been cut by the line and a circumferential curvilinear superficial abrasion/indentation from fishing line encircled the entire distal rostrum. Dissection of the upper aerodigestive tract revealed a large fish hook embedded in the lower blowhole associated with an adjacent abscess at the base of the epiglottis. The stomach contained two unattached fish hooks, parts of a plastic squid lure and two heavy duty work gloves. Further examination revealed a severe necrotising pneumonia with microabscesses in the kidneys and adrenal glands with scattered thromboemboli in keeping with terminal disseminated intravascular coagulation. Death had resulted from septic complications of fishing hook impalement and line entanglement with inanition. The case provides a graphic illustration of the effects of entanglement and fishing hook penetration, as well as ingestion of non-degradable plastic materials, in a free living Bottlenose dolphin.

Cranial crassicaudiasis in two coastal dolphin species from South Africa is predominantly a disease of immature individuals

Crassicauda spp. (Nematoda) infest the cranial sinuses of several odontocetes, causing diagnostic trabecular osteolytic lesions. We examined skulls of 77 Indian Ocean humpback dolphins Sousa plumbea and 69 Indo-Pacific bottlenose dolphins Tursiops aduncus, caught in bather-protecting nets off KwaZulu-Natal (KZN) from 1970-2017, and skulls of 6 S. plumbea stranded along the southern Cape coast in South Africa from 1963-2002. Prevalence of cranial crassicaudiasis was evaluated according to sex and cranial maturity. Overall, prevalence in S. plumbea and T. aduncus taken off KZN was 13 and 31.9%, respectively. Parasitosis variably affected 1 or more cranial bones (frontal, pterygoid, maxillary and sphenoid). No significant difference was found by gender for either species, allowing sexes to be pooled. However, there was a significant difference in lesion prevalence by age, with immature T. aduncus 4.6 times more likely affected than adults, while for S. plumbea, the difference was 6.5-fold. As severe osteolytic lesions are unlikely to heal without trace, we propose that infection is more likely to have a fatal outcome for immature dolphins, possibly because of incomplete bone development, lower immune competence in clearing parasites or an over-exuberant inflammatory response in concert with parasitic enzymatic erosion. Cranial osteolysis was not observed in mature males (18 S. plumbea, 21 T. aduncus), suggesting potential cohort-linked immune-mediated resistance to infestation. Crassicauda spp. may play a role in the natural mortality of S. plumbea and T. aduncus, but the pathogenesis and population level impact remain unknown.

ANESTHETIC MANAGEMENT OF AN INDO-PACIFIC BOTTLENOSE DOLPHIN (TURSIOPS ADUNCUS) REQUIRING SURGICAL DEBRIDEMENT OF A TAIL ABSCESS

This report describes the anesthetic management of a 14-yr-old, 160-kg, female Indo-Pacific bottlenose dolphin ( Tursiops aduncus ) that underwent surgical debridement for a refractory subcutaneous abscess twice within a 6-mo interval. The animal was otherwise in good physical condition at each anesthetic procedure. Following premedication with intramuscular midazolam and butorphanol, anesthesia was induced with propofol and maintained with sevoflurane by intubation. During surgery ventilation was controlled. Blood pressure was indirectly estimated using either oscillometric or pulse oximetry. Presumed hypotension was managed by adjusting the sevoflurane concentration and infusion of dopamine. During recovery, the dolphin regained adequate spontaneous respiration following intravenous administration of flumazenil and doxapram. The dolphin was extubated at 85 min and 53 min after the first and second surgeries, respectively. Successful weaning from the ventilator and initiation of spontaneous respiration was the most important complication encountered. Establishment of a reliable blood pressure measurement technique is critical to success for anesthesia in this species.

Dredging activity in a highly urbanised estuary did not affect the long-term occurrence of Indo-Pacific bottlenose dolphins and long-nosed fur seals

Dredging is an excavation activity used worldwide in marine and freshwater environments to create, deepen, and maintain waterways, harbours, channels, locks, docks, berths, river entrances, and approaches to ports and boat ramps. However, dredging impacts on marine life, including marine mammals (cetaceans, pinnipeds, and sirenians), remain largely unknown. Here we quantified the effect of dredging operations in 2005 and 2019 on the occurrence of Indo-Pacific bottlenose dolphins (Tursiops aduncus) and long-nosed fur seals (Arctocephalus forsteri) in the Port River estuary, a highly urbanized estuary in Adelaide, South Australia. We applied generalised linear models to two long-term sighting datasets (dolphins: 1992-2020, fur seals: 2010-2020), to analyse changes in sighting rates as a function of dredging operations, season, rainfall, and sea surface temperature. We showed that the fluctuations in both dolphin and fur seal occurrences were not correlated with dredging operations, whereas sea surface temperature and season were stronger predictors of both species sighting rates (with seals more prevalent during the colder months, and dolphins in summer). Given the highly industrial environment of the Port River estuary, it is possible that animals in this area are habituated to high noise levels and therefore were not disturbed by dredging operations. Future research would benefit from analysing short-term effects of dredging operations on behaviour, movement patterns and habitat use to determine effects of possible habitat alteration caused by dredging.

Inter- and intra-specific trophic interactions of coastal delphinids off the eastern coast of South Africa inferred from stable isotope analysis

Dietary tracers, such as bulk stable carbon (δ13C) and nitrogen (δ15N) isotopes, can be used to investigate the trophic interactions of marine predators, which is useful to assess their ecological roles within communities. These tracers have also been used to elucidate population structure and substructure, which is critical for the better identification of management units for these species affected by a range of threats, particularly bycatch in fishing gears. Off eastern South Africa, large populations of Indo-Pacific bottlenose (Tursiops aduncus) and common dolphins (Delphinus delphis) co-occur and are thought to follow the pulses of shoaling sardines (Sardinops sagax) heading north-east in the austral winter. Here we used δ13C and δ15N to investigate the trophic interactions and define ecological units of these two species along a ≈800 km stretch of the east coast of South Africa, from Algoa Bay to the coast of KwaZulu-Natal. Common and bottlenose dolphin dietary niche overlapped by 39.7% overall in our study area, with the highest overlap occurring off the Wild Coast (40.7% at Hluleka). Both stable isotopes were significantly enriched in bottlenose dolphins sampled in the western part of our study area (i.e., Algoa Bay and Amathole) compared to eastern animals (i.e., from Hluleka, Pondoland, and KZN). In areas where genetic information is not available or is insufficient, food web tracers (such as stable isotopes) can be used to group individuals based on trophic ecology, which can provide ecological units for management of populations. The distinct isotope signatures found here for bottlenose dolphins can, therefore, be used as management units for conservation efforts in the future.

Dolphins, sharks, and barnacles: Use of photographs to examine intra- and inter-specific interactions in bottlenose dolphins in Mozambique

Understanding interactions within and between species is crucial to ecological research. However, for cetaceans such interactions can be difficult to observe in the field. Photographs offer an opportunity to study intra- and inter-specific interactions, by capturing 'snapshots' of their occurrence over space and time. At-surface and underwater photographs of bottlenose dolphins (Tursiops aduncus) inhabiting Ponta do Ouro Partial Marine Reserve (PPMR), Mozambique, were used to examine evidence of interactions with other dolphins, predators and ectoparasites. Intra-specific scarring levels significantly differed by sex and age class, with males displaying more scarring than females. Similarly, adults had more scarring than juveniles or calves. Shark bites significantly differed in their distribution across dolphin body areas, with the dorsal side being more frequently wounded than the ventral side. The presence of barnacles was exclusive to fluke, dorsal and pectoral fins, and showed strong seasonal trends. Overall, this study demonstrates the value of photographs for examining marine ecological interactions. It provides the first insights regarding dolphin social behaviour, predation risk and health for this population. These in turn will support future research into the population dynamics and conservation of the PPMR dolphins, which is urgently required in the face of locally increasing anthropogenic pressures.

Long-Term Demographic Trends of Near Threatened Coastal Dolphins Living in an Urban Estuary

Understanding population demography of threatened species and how they vary in relation to natural and anthropogenic stressors is essential for effective conservation. We used a long-term photographic capture-recapture dataset (1993-2020) of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the highly urbanised Adelaide Dolphin Sanctuary (ADS), South Australia, to estimate key demographic parameters and their variability over time. These parameters were analysed in relation to environmental variables used as indicators of local and large-scale climatic events. Our findings indicate that apparent survival was high (0.98-0.99) and did not vary seasonally. Estimates of abundance were not directly related to environmental variables but were linked to seasonal temporary emigration. Abundance peaked in summer with an average of 85.37 dolphins (SD = 30.23) and was lowest in winter, with 68.57 (SD = 24.70) individuals. Site fidelity at the population level was low, but lagged identification rates revealed a population of approximately 28 individuals at any one time. Trend analysis suggests an increase in dolphin abundance from 1993 and persistence of the population over decades despite significant urbanisation, although numbers have declined in more recent years. Further research is needed to understand the cumulative impacts leading to this population decline and to assess its future viability under different management scenarios. Conservation strategies aimed at increasing reproductive rates and promoting connectivity to adjacent waters are likely to be more effective in reversing population declines.

Histomorphological stratification of blubber of three dolphin species from sub-tropical waters

Blubber is a highly specialised and dynamic tissue unique to marine mammals and presents a reflection of the individuals' nutrition, environment, and life history traits. Few studies have investigated the histomorphology of cetacean blubber in sub-tropical environments. The aim of this study was to investigate the blubber histomorphology of three different dolphin species off the sub-tropical KwaZulu-Natal coast, South Africa, using adipocyte cell size, number and density. Blubber tissue samples from the saddle area of 43 incidentally bycaught animals (4 Sousa plumbea, 36 Tursiops aduncus and 3 Delphinus delphis) were used to compare cell parameters between blubber layers. Samples were divided into upper third (corresponding to the superficial layer closest to the epidermis), middle third, and lower third (corresponding to the deep layer). For T. aduncus, factors potentially affecting blubber histomorphology, such as sex, age class and season, were also assessed. Our results showed that no stratification was present in S. plumbea, which could be ascribed to the species' warmer inshore habitat, large body size and apparent lower mobility. For T. aduncus and D. capensis, however, blubber stratification was determined, characterised by a gradual transition of cell size, number and density between layers rather than clearly defined layers. Significant differences in adipocyte cell number and density were found for different sexes and age classes of T. aduncus. However, there were no significant differences between seasons, which was attributed to the small temperature differences between seasons. This study represents the first investigation on odontocete blubber histomorphology in subtropical waters. It is recommended that future studies investigate blubber lipid content, while also taking into consideration the reproductive status of the females and the temperature range of their study area. It is hoped that our results, in conjunction with histopathology and other health indicators, could assist in assessing health and body condition. This article is protected by copyright. All rights reserved.