Authorities are investigating the death of thousands of leatherjacket fish washed onto beaches in New South Wales and Queensland.
The fish, mostly juvenile, have appeared on hundreds of beaches on NSW’s south coast and on the Sunshine Coast after ex-Tropical Cyclone Alfred.
A spokesperson for the NSW department of primary industries and regional development said the department was investigating reports of dead fish washed ashore along a 140km stretch of the south coast, from Lake Conjola to Narooma, and including the popular fishing spots of Batemans Bay, Ulladulla and Lake Tabourie.
“Current reports are estimating numbers in the thousands of fish, mostly juvenile leatherjacket washed up on several south coast beaches, with the cause currently unknown,” they said.
“Samples have been taken to determine the cause of the mortalities and Fisheries officers are continuing to monitor the areas for any further events.”
There are more than 20 species of leatherjacket found in NSW waters, according to the state government. The fish can be recognised by their small mouth, “beak-like teeth” and thick, rough skin.
A Sunshine Coast Council spokesperson confirmed numerous reports of leatherjacket fish washing up on beaches in south-east Queensland in the past fortnight.
“Leatherjackets, which belong to the family Monacanthidae, are commonly found in Australian waters and are known for their tough, leathery skin and distinctive spine,” they said.
“The reasons for these strandings can vary. Environmental factors such as changes in water temperature, pollution or natural events like ex-Tropical Cyclone Alfred can contribute to leatherjackets and other fish species washing up on shore.”
Leatherjackets were part of a mass fish kill in Victoria’s far-east Gippsland in 2017. The Victorian Fisheries Authority said a rapid drop in water temperature killed the fish.
Thousands of fish deaths have also been recorded along the Richmond River at Ballina in northern NSW in recent days, with flathead, bream, whiting, prawns and other marine life washed ashore.
Waterways protection group OzFish attributed the fatalities to flooding on the northern rivers before and after ex-Tropical Cyclone Alfred, which helped create a “blackwater” event, where organic material was washed into waterways.
A spokesperson for Ballina Shire Council confirmed Alfred had affected water quality and low oxygen levels, causing fish kills. “With widespread impacts, these conditions are likely to continue in the coming weeks,” they said.
A similar fish kill happened in 2022, after another severe flooding event in the northern rivers.
