18-05-2025
Sad discovery at popular Aussie river sparks concern amid 'disturbing' trend
"Disturbed" locals have reported that hundreds — and possibly thousands — of small dead fish are washing up ashore along a popular Australian waterway in the country's south.
Numerous dead fish have been spotted floating along the River Derwent in Tasmania over the weekend, sparking an investigation by environmental authorities.
The fish, believed to be pilchards or sardines, were seen strewn along the water and beaches between Crayfish Point in Taroona and Long Beach in Sandy Bay on Saturday. The sight alarmed local residents, many of whom shared their concern on social media.
Initial testing by Biosecurity Tasmania and the Environment Protection Authority (EPA) detected the presence of pilchard orthomyxovirus (POMV) — a virus known to naturally occur in several fish species found in Tasmanian waters — in samples collected over the weekend, Pulse Tasmania reported.
The virus belongs to the same broader family as influenza but only infects aquatic species, with Atlantic salmon and Australian pilchards being particularly vulnerable.
While it often exists in the environment without causing major issues, outbreaks can occur when fish are stressed due to environmental factors like warm water temperatures, low oxygen levels, or handling. These outbreaks can lead to symptoms such as lethargy, unusual swimming behaviour, reduced appetite, and, in severe cases, large-scale fish deaths.
In recent months, mass fish deaths have been reported along Australia's coast. In March 2025, thousands of juvenile leatherjacket fish washed up on beaches stretching over 300 kilometres from Stanwell Park to Bermagui in New South Wales.
Similarly, in South-East Queensland, reports emerged of leatherjacket fish washing ashore, with environmental factors such as changes in water temperature, pollution, or natural events like ex-Tropical Cyclone Alfred potentially contributing to the strandings.
In South Australia, a toxic algae outbreak was responsible for the deaths of numerous marine life. Among them were different species of fish, octopus and cockles (also known as pipis).
The Department of Natural Resources and Environment Tasmania confirmed that tests for illnesses typically associated with farmed salmon, including Tasmanian rickettsia-like organism (TRLO) and P. salmonis, returned negative results.
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While the current fish kill appears to be localised, further testing is now underway to determine whether other contributing factors may be involved. Officials are also monitoring nearby marine environments to assess the potential impact on other species.
Environmental scientists said it's still unclear whether the event was an isolated incident or could indicate deeper ecological issues within the Derwent Estuary.
In early 2025, Tasmania experienced a significant environmental crisis as large numbers of dead salmon and oily fish waste began washing up on beaches in the state's southeast, including Verona Sands and Bruny Island.
These incidents were linked to a mass mortality event in nearby salmon farms, where over 5,500 tonnes of fish died in February alone—approximately six per cent of the industry's annual production.
The primary cause of the die-off was an outbreak of Piscirickettsia salmonis, a bacterial infection exacerbated by rising water temperatures. As the infected fish decomposed, congealed fish oil and fatty, "foul-smelling" deposits formed, which then drifted ashore.
Preliminary testing by the Environment Protection Authority (EPA) confirmed that these greasy "chunks" were composed of fish oil mixed with sand.
Despite the decline in fish deaths, the incident has raised ongoing concerns about the sustainability and environmental impact of salmon farming in Tasmania. Calls for increased transparency and stricter oversight continue as the community seeks to prevent similar events in the future.
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