The cause of a mass fish death event at Eight Mile Creek, east of Port MacDonnell, may not been known for up to two weeks.
On Monday the Department of Primary Industries and Regions (PIRSA) received reports of a fish mortality event involving a range of species, mainly wobbegong shark but also including snapper, wrasse, octopus, port Jackson shark, stingrays, Australian salmon and ling fish.
Fish kill events can be brought on by a variety of causes including environmental factors such as temperature, rainfall (or lack of) and water quality including salinity or oxygen levels, or by disease or pollutants.
The department said while it was investigating the incident, the cause has not yet been confirmed, however early indications based on water testing are that low salinity caused by recent high rainfall is the most likely reason for the fish mortality event.
PIRSA has collected tissue samples to rule out aquatic diseases and testing is underway.
PIRSA Senior Biosecurity Officer Dr Chloe McSkimming said up to 100 carcases had washed ashore earlier this week.
“When Fisheries officers have been monitoring the area the individuals they have seen have been dead, it’s likely they’ve been washed ashore dead, but we are unable to tell that yet, but they haven’t been seen alive,” she said.
“The Department of Primary Industries and Regions investigates 15-20 fish kill reports around SA each year and they can occur in both fresh water and marine waters.
“I’m aware of one that did occur early last year (in the Limestone Coast) and PIRSA was notified via a call to our FISHWATCH hotline and we did investigate, that likely cause was put down to environmental conditions.
“You can get a decrease of salinity following heavy rainfall if there is creek in vicinity, there is Eight Mile Creek in this vicinity which would have flushed out into that environment which would have caused the low salinity levels that we have recorded.”
Dr McSkimming said Fisheries officers had taken samples from several of the different species that had washed ashore for testing.
“With those types of samples those specimens need to be very fresh to be viable for testing, the Fisheries officers chose the most recent dead species to ensure viability,” she said.
“Microbiology and diagnostic results can take several weeks to receive results depending on the kind of testing they need to do.
“It is generally up to about two weeks, it depends on the type of test they are running … and we do send them to Gribbles vet lab in Adelaide.”
Dr McSkimming said Fisheries officers were keeping an eye on the beach to see if any further dead fish washed ashore.
“The tidal movement is increasing in the area from today and we are hoping this will help to dilute the water and take what is on the beach off the beach, that is something we are monitoring,” she said.
“I would like to remind people if they do notice anything unusual to call our FISHWATCH hotline on 1800 605 522.”
