About 1.35 million farmed salmon have died due to disease in Australia's Tasmanian harbour, prompting the state environmental regulator to slash the total amount of fish stock by 20 per cent.
The mass deaths between October and May at the picturesque Macquarie Harbour on state's west coast, adjacent to the Wilderness World Heritage Area, was confirmed by Tasmania's Environment Protection Authority on Tuesday.
It also announced a reduction in the amount of fish to be farmed from 12,000 tons to 9,500 tons to rehabilitate the area, which has been suffering from environmental damage and mass deaths due to overstocking for years.
"My view is that it is prudent to adopt an approach which reduces the biomass for a sufficient time to allow harbour response to be monitored and interpreted meaningfully," Wes Ford, the agency's director, said in a statement on Tuesday.
The salmon deaths were mainly due to an outbreak of endemic pilchard orthomyxovirus (POMV), transferred from the wild populations, Australian broadcaster ABC said, citing a report that has not yet been made public.
"POMV can be exacerbated by stress caused by heat, low oxygen, and I think this summer we've seen some elevated temperatures and clearly some concerns about oxygen," Ford told local ABC radio.
Environmentalists called for the entire harbour to be cleared of salmon farming to allow it to recover completely.
"We have to have a moratorium on all fish farming. The salmon farming companies have to get out of Macquarie Harbour," the Greens party's environment spokeswoman Rosalie Woodruff said. "It's clearly the case that the system there is damaged, possibly beyond repair."
