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Adelaide Dolphin Sanctuary Investigation

Adelaide Dolphin Sanctuary Investigation

The Minister for Environment and Water David Speirs MP launched an investigation on 24 August 2021 into the potential causes of recent dolphin deaths in the Adelaide Dolphin Sanctuary (ADS).

The investigation, which is expected to take several months to complete, aims to identify the sources and rationale for what could be impacting the health of dolphins and ecosystems within the Port River and Barker Inlet. It also includes evaluating historical data and necropsy results from recent dolphin deaths.

It is being coordinated by the Department for Environment and Water, in conjunction with a range of expert partners, including:

  • National Parks and Wildlife Service’s Dolphin Expert Reference Group (made up of independent, qualified veterinarians)
  • Australian Marine Wildlife Research & Rescue Organisation Inc.
  • experts in the management of marine mammals
  • researchers from the University of Adelaide, Flinders University and the South Australian Museum
  • authorities from other relevant government departments, including the Environmental Protection Authority (EPA) and Department of Primary Industries and Regions (PIRSA).
  • CSIRO
  • ZOOS SA
  • Port Adelaide Enfield Council
  • Whale and Dolphin Conservation.

More information

23 November 2021

A four-year old male dolphin, known as Squeak (Mimo), was found dead late Sunday afternoon near the Fletcher’s Slip area of the Port River by the National Parks and Wildlife Service (NPWS) Marine Parks team. A post mortem will be carried out by experts at the University of Adelaide, Flinders University and the South Australian Museum. The findings will contribute towards the ongoing investigation into what might be impacting the health of dolphins in the sanctuary.

The interim investigation report into the health of dolphins in the Adelaide Dolphin Sanctuary (ADS) was released, along with the interim necropsy reports.

Initial testing of the three recent dolphin deaths (‘Tallula’, the ‘Semaphore dolphin’ and ‘Hunter’) indicated the dolphins were suffering from infections and diseases that affected their health with varying degrees of severity. The reports don’t show a definitive cause or common links between the dolphin deaths beyond possible suppression of their immune systems.

Further testing for environmental toxicants (including biotoxins) and factors that may contribute to immunosuppression is underway, involving experts in water quality, toxicology, pathology and marine ecosystems. The investigation team has also expanded their field of investigation and are drawing in additional resources and expertise from around the nation to conduct further tests and analyse data.

Blood and tissue testing from dolphin, ‘Doc’, showed he had been exposed to Brucella, a zoonotic bacterium that can result in dolphin abortions, male infertility, neurobrucellosis, cardiopathioes, bone and skin lesions, and death. While known to occur in marine mammals, this is the first time Brucella has been detected in a South Australian dolphin. Doc was tested while being disentangled from fishing line, but has only been sighted once since then.

Broader surveillance will be required to understand whether Brucella could be impacting the health of dolphins, particularly whether or not it is contributing to calf mortality within the Sanctuary.

11 November 2021

Hunter tested negative for Brucella, a bacterial infection which can be found in bottlenose dolphins.

Prawns found in Hunter’s stomach were identified as two local endemic species. Research based on stomach contents analysis of ADS dolphins during past necropsies has found that prawn is not considered part of an ADS dolphin’s typical diet. Foraging would have been atypical, with it being difficult for the animal to catch fish while he was unwell, which may explain why prawns were found in its stomach.

Toxicology testing will be expanded to include potential contaminants that could enter the area from stormwater and waste water treatment plant outflows.

Long-term population analyses of ADS dolphin survey data collected by Rangers has commenced.

A literature review is being undertaken by scientists at the South Australian Research and Development Institute (SARDI) which will examine the themes raised in the conceptual model and provide comparisons to other urban dolphin populations.

The refining of age at time of death/emaciation indices at time of death/summary of pathologies for ADS dolphins from past 20 years is underway.

The investigation team discussed the benefits and disadvantages of taking blood samples from live wild dolphins which show signs of illness. Where skin lesions are present these could be sampled, however lesions are usually a secondary affliction which is usually not responsible for cause of death in dolphins. Blood samples may provide an insight that the animal is fighting an infection (i.e elevated white cells) however in cases where there is an isolated infection (i.e. ear infection) this may not necessarily be reflected in the blood samples.

The expert team noted that as causes of death by disease cannot currently be attributed to a specific cause, and that immune system deficiency may be an underlying issue for the ADS population, the benefit of undertaking stressful operations to capture animals for testing is not recommended at this stage.  

27 October 2021

The post mortem of ADS resident dolphin, known as Hunter, found the animal was in very poor health and was unlikely to have lived much longer.

The necropsy report, prepared by the University of Adelaide in conjunction with the South Australian Museum, showed six-year old Hunter had multiple infections which were adversely impacting him, and were likely connected to his recent and significant weight loss.

The presence of toxicants including PFAS (per- and polyfluoroalkyl substances), heavy metals and other persistent pollutants are expected in a species such as dolphins that live in a large urban center like Adelaide and because they are long lived predators. The extent to which these could be impacting the health of the dolphins is being explored through these studies.

An additional set of broader range tests are now underway by expert laboratories across Australia, including testing for environmental toxicants and factors that may contribute to immunosuppression, involving experts in water quality, toxicology, pathology and marine ecosystems.

The additional testing is intended to provide further detail about the health of these animals and the environment in which they are living and test the potential role of these toxicants on immunosuppression. The immune system is a vital defence for the dolphins.

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22 October 2021

The investigation has been expanded after a 6-year-old dolphin, known as Hunter, was assessed by independent veterinary experts and subsequently euthanised due to ongoing deteriorating health.

Hunter had been observed looking very thin, with a lesion on its flank, raising concerns about the animal’s health. In recent weeks, the dolphin had been reported as appearing lethargic, emaciated, and spending more time than usual on the surface. 

Following consultation with an expert wildlife veterinarian, the Department for Environment and Water decided to euthanise the dolphin to prevent further suffering.

The body was retrieved for testing in the hope that the tests will provide further insight into the health of the ADS dolphin population as part of the ongoing investigation.

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5 October 2021

The dolphin ‘Tallula’ (a 12 year old, sub-adult male) was found deceased and in an emaciated condition in Angas Inlet by rangers and community members. No obvious disease or cause of emaciation was found during post mortem.

Further testing is now underway and tissue samples have been sent to specialist labs interstate as part of the investigation. Due to COVID-19 restrictions and interruptions to business-as-usual, DEW cannot at this stage place a timeframe on when we expect to receive the results.

Once the post-mortem has been completed, the SA Museum will work with DEW, Flinders University and the University of Adelaide to analyse the findings.

24 September 2021

An expert workshop was held on 17 September 2021 to help authorities better understand the functions and current threats to the Adelaide Dolphin Sanctuary’s ecosystem.

Representatives at the workshop included:

  • Department for Environment and Water
  • Environment Protection Authority
  • SA Museum
  • Adelaide University
  • Flinders Ports
  • Flinders University
  • Australian Marine Wildlife Research and Rescue Organisation
  • Primary Industries and Regions SA - Fisheries and Aquaculture

Workshop participants reviewed historical data and identified trends and patterns corresponding to the dolphin deaths. A common understanding on how the ecosystems within the sanctuary work was developed, this included identifying what pressures affect them and how dolphins interact with these.

A report is now being prepared along with a conceptual model of the Port River and Barker Inlet ecosystem. Key findings from the necropsies and pathology tests and recommended next steps will also be included. 

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