A mass fish kill at Little Swanport on Tasmania’s east coast was most likely caused by low oxygen levels, Fisheries Tasmania says.
Around 3,800 dead fish were removed from the river, with southern black bream making up most of the deaths.
Staff from the Inland Fisheries Service and the Department of Natural Resources and Environment carried out clean-up, monitoring and investigation work across the affected area.
Water samples and fish specimens were also collected for laboratory testing.
“While the test results were inconclusive, current evidence indicates the mortality event was most likely associated with low dissolved oxygen levels,” Fisheries Tasmania said on social media on Friday.
“Dissolved oxygen concentrations measured following the event were found to be very low, supporting this assessment.”
Drone surveys found no other mass fish kills downstream of the bridge.
On-ground surveys also found large schools of healthy bream, mullet, toadfish and galaxiids upstream, with “no obvious signs” of ongoing poor conditions.
The findings are in line with an early assessment from recreational fishing body TARFish, which said warm conditions, low flows and decaying vegetation may have stripped oxygen from the water.
Fisheries Tasmania thanked community members who reported the incident and provided information during the investigation.
