Latest news with #RiverDerwent
ABC News
19-05-2025
- Health
- ABC News
Pilchard virus present in dead fish in Hobart, as authorities say salmon bacteria not to blame
Dead fish, believed to be pilchards that washed ashore on southern Tasmanian beaches on Saturday have tested positive for pilchard orthomyxovirus. But experts say the disease that caused the recent death of large quantities of salmon is absent. Investigations are continuing into how the most recent deaths occurred, with other scientists noting temperature changes and other environmental conditions as possible factors. Experts say there is no evidence to suggest any risk to humans from pilchard orthomyxovirus (POMV). Large numbers of dead fish were seen by locals floating in the River Derwent and lining the foreshore from Sandy Bay to Taroona at the weekend. Sandy Bay resident David Boyles said the sight was "distressing". Mr Boyles inspected the fish on the rocks in front of his home and said many appeared to be bleeding from their gills and vents. The Natural Resources and Environment Department (NRE) has confirmed Piscirickettsia salmonis (P. salmonis) disease, which made headlines earlier this year, has not been detected. NRE also said it was conducting "further testing, including the confirmation of the fish species". Francisca Samsing, a veterinarian and senior university lecturer in aquatic animal health at the University of Sydney, said POMV was first detected in healthy pilchards in Australia in the 1990s. Dr Samsing said the virus was "generally isolated in healthy animals" and that it "requires other conditions, or it requires a jump to another host to cause disease". "What may be triggering this might be environmental events that add additional stress to fish, making them get sick," Dr Samsing said. She said temperature and the level of dissolved oxygen in water "generally plays a big role in aquatic systems". "We don't know the extent of what's happening now until our colleagues at the NRE do the sequencing and understand if there have been changes to the virus recently," she said. "In autumn, it's not uncommon to see 'hypoxic events' [when] water at the bottom, which is low in dissolved oxygen, might come up to the surface due to big tides — what we call the 'spring tides' or the 'king tides' which follow the full moon. Marine biologist at the Institute of Marine and Antarctic Science (IMAS), Neville Barrett, similarly told ABC Local Radio that while the disease causing the mass deaths was "definitely possible", "all sorts of things" could have been behind it."The Derwent itself is actually remarkably colder — now on the surface — but in particular, than the ocean, where the pilchards typically come from," Dr Barrett said. Dr Samsing said monitoring the environment was important as "problems in waterways can cause big fish kills". "We've seen that here in New South Wales where I'm based now, many times associated with pollution and loads of oxygen and things like that," Dr Samsing said. According to the Fisheries Research and Development Corporation (FRDC), POMV has become a "persistent issue" for Atlantic salmon since its first detection in South Australia in 1998. In 2012, the FRDC said a POMV outbreak in the Huon River, in south-east Tasmania, resulted in "significant" Atlantic salmon mortalities. In 2018, an outbreak in Macquarie Harbour on Tasmania's west coast, killing 1.35 million salmon and prompting one company, Petuna, to cull two fish pen populations to reduce the disease spread. Dr Samsing said a vaccine had since managed to combat the virus in the aquaculture industry, but it was not as easy for the natural environment. "More broadly, we're seeing more and more … die-off events and mortality events associated with viruses around the world," Dr Samsing said. "In wild reservoirs, so in pilchards and sardines, there's not much you can do. I mean, we can all contribute to the reduction of climate change and things like that." Dr Samsing said the salmon farming industry had "developed a very effective vaccine that has protected fish for a long time". NRE said Biosecurity Tasmania and the Environment Protection Authority were continuing to investigate the weekend fish deaths.
Yahoo
18-05-2025
- Health
- Yahoo
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. Locals 'not happy' as mysterious 'foul-smelling chunks' wash up Senator slammed for car park claim after salmon disease outbreak 'Disgusting' photos of popular Aussie food spark furious debate 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. Do you have a story tip? Email: newsroomau@ You can also follow us on Facebook, Instagram, TikTok, Twitter and YouTube.
ABC News
18-05-2025
- Science
- ABC News
Fish believed to be sardines or pilchards wash up in the hundreds in Hobart
Hundreds of small, dead fish seen floating and washing ashore on the River Derwent near Hobart on Saturday have raised concerns with some local residents. The fish, seen along the shore between Crayfish Point in Taroona and Long Beach in Sandy Bay, are believed to be pilchards or sardines. David Boyles lives by the water in the Hobart suburb of Sandy Bay and has fished in the Derwent River for years. Mr Boyles said on Saturday morning he noticed "little shiny, white-looking things on the rocks down below our house". Along with the dead fish seen on the rocks, Mr Boyles said, "were hundreds if not thousands more, just floating in the water, dead". He said he was distressed to see that about a third of the third appeared to be bleeding from their gills and vent, leading him to think it was "some kind of toxic event". He said a man kayaking on the river towards Hobart told him there were many more down river. The Environment Protection Authority (EPA) and Institute of Marine Antarctic Science (IMAS) have been contacted for comment. Independent water scientist Christine Coughanowr has spent years monitoring the River Derwent. For 20 years, she led the Derwent Estuary Program, which focuses on monitoring and restoring water quality of the estuary. Ms Coughanow said while the incident had worried some, it was too early to draw conclusions. "I think really that raises in some ways more questions than it answers." She said it was still unknown if other marine species were impacted, and how widespread the issue was. "I think really the key question is for those who have the ability to assess this, the EPA and the fish health authorities, to get the samples and do the necessary analysis to find out what's going on," Ms Coughanowr said.
