Adelaide Dolphin Sanctuary Investigation

Investigation update

A report by the South Australian Research and Development Institute - Review of threats to dolphin health in the Adelaide Dolphin Sanctuary – is now available. View here.

The report examines dolphin health literature from around the world along with data and reports about the local population, providing a robust review of potential threats to ADS and coastal dolphins to inform the investigation. The report also highlights similar dolphin mortality events around the world and how difficult it can be to find a definitive cause of these events.

The final investigation report is expected to be completed by late 2022.

Latest necropsy results

Necropsy results for Namor, an ADS resident dolphin found deceased in March, have failed to find a single definitive cause of death. View here.

The post-mortem examination showed bruising on Namor’s lower jaw which could indicate trauma from an unknown cause. However, this was not considered significant enough to have caused death and definitive diagnosis is pending further examination and infectious disease screening test results. The presence of an abscess in the left lung also requires further investigation to rule out a bacterial infection.

Recent fatalities

National Parks and Wildlife Service rangers recovered an approximately two-month-old, deceased common dolphin calf from the Port River Estuary on the 8 May. The deceased dolphin calf was found dead within the St Kilda channel. Common dolphins are a different species to the resident ADS bottlenose dolphins and are typically found in deeper waters but are occasionally sighted within the ADS. There were no obvious external injuries. A necropsy is being undertaken to see if a cause of death can be determined.

Four-month-old calf Saki has not been sighted with its mother, a 38-year-old female named Dinah. As this calf was still dependent on its mother, this observation would suggest Saki is deceased. There is no evidence to suggest this is linked to the other deaths being investigated. Several other calves have been sighted in the outer waters recently, and ongoing surveys will endeavour to record photos for future identification.

In August 2021, the Department for Environment and Water initiated an investigation into the deaths of a number of dolphins in and around the Port River and the Adelaide Dolphin Sanctuary.

The investigation sought to identify what could be impacting the health of the dolphins by evaluating historical data, extensive testing, and autopsy results from recent dolphin deaths.

Disappointingly, the investigation is yet to determine a definitive cause of the deaths, though stress and toxins have been identified as potential contributors. Further analysis of toxicology results is still underway along with other lines of inquiry.

In addition, other longer term studies are being undertaken in partnership with Flinders and Adelaide universities, the SA Museum and the EPA to explore potential food chain and water quality factors.

The DEW investigation team will hold two further workshops to review all available data and key findings before finalising its report and recommendations to the Minister for Environment which is due by mid-year.

As part of the investigation into dolphin deaths in the Adelaide Dolphin Sanctuary, extensive testing is being undertaken from the bodies collected and also the environment.

This testing has been carried out by independent laboratories and agencies. Preliminary results were received in late December 2021. Further test results were received in February 2022.

Chemicals of emerging concern (also called "contaminants of emerging concern" or "CECs") can include pharmaceuticals, personal care products, flame retardants, detergents, and per and polyfluorinated alkyl substances (PFAS) with potential to enter the environment and cause known or suspected adverse ecological and/or human health effects.

We carried out extensive analysis to reveal bioaccumulation of heavy metals, persistent organic pollutants and selected CECs in dolphins. The full suite of chemical residues in the liver of Hunter, Tallula and the Semaphore dolphin were analysed by the National Measurement Institute and the Department of Industry, Science, Energy and Resources.

Results

Emerging contaminants such as phthalates, short-chain paraffin, and pesticides were below the detection limits in the liver samples of the two ADS dolphins.

Trace metals and some persistent organic contaminants were detected at low concentrations. The levels detected are similar or lower than what has been reported by other monitoring studies of Gulf St Vincent bottlenose dolphins. For example, PFAS levels were monitored in the nine dolphin liver samples from the Port River & Barker Inlet by SA EPA (2017). As perfluorooctane sulfonic acid (PFOS) contributes greater than 90% of the total PFAS, we compared the results in both studies. SA EPA study reported PFOS levels ranging between 510–5,000 µg/kg and an average of 1986 µg/kg. In the current study, PFOS levels in the livers from the two dolphins varied between 300- 430 ug/kg. The data indicates PFOS levels are declining in Port River dolphins, which is consistent with PFOS being phased out of industrial and firefighting applications. Although the current set of data is based on only two samples.

It is unclear whether the contaminants of concern measured in the current investigation are having any adverse effect on the dolphins at these concentrations. To understand the implication of the detection of multiple contaminants in dolphin livers, we are planning further monitoring studies to assess the levels of these contaminants in the food sources of the dolphins including marine invertebrates and fish at different trophic levels.

Historical study findings

In all of the recent dolphin deaths, there has been a commonality of poor body condition at the time of death, this has led the investigation team to question whether this is a new symptom at time of death or has been observed in the past too.

The SA Museum recently completed a body condition analysis on ADS dolphins from the 1987 to 2021. The report is based on specimens lodged in the SA Museum collection and is based on the external appearance of whole dolphins. A total of 52 dolphins were included in this summary. “The summary found that all time periods recorded moderately/very emaciated dolphins but the proportion appears to have been greater since 2005. The assumption is that the data after 2005 are the most meaningful because observer effort is likely to have been consistent after the creation of the ADS in 2005. One of the limitations of this study is that it does not take into account the dolphins that disappeared (died or emigrated) from the ADS”.

Next steps

A number of studies have been initiated to examine potential causes of dolphin deaths.

Toxicological studies and the autopsies of the recent mortalities have not identified a single common cause of death for all animals. Current expert advice indicates immunosuppression as a key factor and investigations into possible causes, such as long lived chemicals and pollutants present in the ADS environment are being followed up. Studies now underway, seek to provide greater insight into the presence of and possible pathways of a variety of pollutants affecting the dolphins, through both toxicology studies of dolphin samples, sampling of fish (food pathways) and reviewing past studies of dolphins, sediments and water.

The pollution and other studies are complemented by a series of longer term examinations of the Port River dolphin population and their associated environment in collaboration with Adelaide and Flinders Universities. These studies will continue for the next three years.

The ADS investigation team (currently comprising more than 30 members who are experts in their respective fields) will continue to meet regularly to guide the studies and produce a report of the outcomes.

On behalf of DEW, the South Australian Museum has carried out a preliminary necropsy of Squeak and has conclude that the most likely circumstance for the dolphin is ‘Unknown (blunt trauma, probable chronic condition)’.

Further tests are still underway and next report will be available when more results will be out.

Download the SA Museum necropsy report.

Disease testing continues by the Australian Centre for Disease Preparedness, the national veterinary testing laboratory specialising in viral diseases, based in Geelong. The tests include a range of pathogens, viral diseases such as influenza and several other viruses that can cause disease in dolphins. Full results are expected to be availableby the end of the year.

Hunter‘s lung test results were negative for cetacean morbillivirus and Influenza A test. Further viral testing of the brain will be conducted to investigate for chronic morbillivirus, that may be associated with immunosuppression.

Toxicology testing has been widened, which in some instances has meant that testing methodologies have had to be sought out and developed specifically to determine the accurate testing for emerging pollutants on marine mammals. For example, analytical methodologies are not yet validated for analysing emerging pollutants in biota such as marine mammals (current methods only exist for abiotic media, such as water and sediments). We are working with the NATA accredited national laboratory to develop reliable methods for measuring these emerging chemicals in biota. Only selected interstate specialist labs have the capability to run these tests and produce reliable data.

Biotoxin testing is underway to determine if harmful algal blooms, caused by the excessive growth of phytoplankton, may contain highly toxic chemicals. An increase in nutrients or changes in water temperatures can cause algal organisms to increase and produce these biotoxins that can affect dolphins.

Water samples collected by Flinders University at Garden Island and Snowden Beach (in the ADS) were analysed for phytoplankton species through the NATA-accredited microalgal services laboratory in Melbourne. The Garden Island sample revealed the presence of two potentially harmful species of phytoplankton (a dinoflagellate Dinophysis acuminata and a diatom Pseudo-nitzschia pungen/multiseries). However, while the phytoplankton were found within the water sample, their biotoxins were not detected within liver samples from Hunter, Tallula or the Semaphore dolphin as examined by PIRSA (SASQAP, Port Lincoln). The Snowden Beach sample didn’t detect the two phytoplankton species.

A post-mortem examination of Squeak was conducted by the SA Museum and the University of Adelaide, with final testing still underway. Initial findings from the necropsy report showed that Squeak’s body was very emaciated. There was severe deep blunt trauma observed on the right side of the head and neck area, but no obvious external injuries, therefore the cause is unknown. Bacteria were identified from ear, lung and skin. Some bacteria were pathogenic (disease/infection), some were likely to be secondary and not related to the cause of the death. A full necropsy report will be available following the analysis of test results (for diseases, histology and bacteria) and more detailed analyses of organs.

Despite Squeak’s emaciation, his stomach appeared to contain solid material, and faeces were found in the intestines. The spleen was atrophied and adrenals were enlarged. A chronic condition may have been evident, but there were no signs of significant infection. The stomach contents of Squeak will be analysed by specialist researchers.

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.

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.

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.

Read more

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.

Read more

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.

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.