Fish
Diagnostic tests of fish samples collected to date have ruled out infectious fish diseases.
Pathology results have indicated prolonged stress and gill irritation consistent with unusually high water temperatures and possible harmful algae.
While water testing is ongoing, no known toxic algae have been identified to date. However a well known harmful algae, Chaetoceros (diatom) has been observed in samples. This species of algae causes harm to fish through abrasion, and is a well known cause of fish kills around the world.
It is important to note that Chaetoceros (diatom) is not harmful to humans, so there is no danger in continuing to catch and eat fish.
Biosecurity SA is currently awaiting results from some recent samples taken from the Yorke Peninsula, which this week saw a small number of fish, mainly leatherjackets, found dead. These samples have been sent to pathology for testing. We are also expecting the results of an independent assessment on water samples collected over the past three weeks. The results are expected soon.
As previously indicated, water temperature has been a significant factor to date, and it is also important to note that sea water takes a long time to cool down so a change in wind direction and air temperature does not immediately translate to cooler water.
As already reported, satellite imagery for March confirmed the presence of algal blooms. PIRSA has received and is currently analysing wind strength and direction data for the period 14 February to end March to assess conditions favourable for oceanic upwellings, which coupled with increased temperature supports algal blooms.
We encourage members of the public to continue to report anything of concern to Fishwatch, so that scientists can investigate.
Dolphins
The SA Museum continues to conduct post-mortems on the dolphin carcasses and is awaiting the results of tests to determine cause of death. Until we know the cause of death, it is impossible to say why they are still being found.
Rangers from the Adelaide Dolphin Sanctuary collected a young dolphin from Port Noarlunga beach on Wednesday 17 April. DEWNR rangers also retrieved a dead dolphin from Granite Island, at Victor Harbor on Tuesday 16 April.
A dolphin was found at Canunda in the South East on Wednesday, but that is well outside the range of where the others have been found. This brings to 26 the total number of deceased dolphins found dead since March 1.
Preliminary test results from the dolphin post-mortems are expected in about two weeks.
Health information: Algal blooms that cause fish deaths through oxygen depletion and gill damage do not affect human health through recreational use of water.
Further information:
Updates will continue to be made available at: www.pir.sa.gov.au/fishmortalities
Report significant fish deaths to Fishwatch (24 hours) 1800 065 522
Scott Ashby
Chief Executive
Primary Industries and Regions SA