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The Australian grayling – one of Victoria's threatened fish species – continued to prosper in Gippsland's Thomson River as a direct response to environmental watering in 2014–15.

Environmental watering specifically targeted Australian grayling in the Thomson River which is home to one of the few remaining self-sustaining populations of this native fish.

Freshes -  watering that exceeds the base flow, lasting for one or several days - were delivered in autumn to trigger migration and breeding of native migratory fish. Freshes were again released in spring to encourage the recruitment of juvenile native fish back into the Thomson system.


Minna Tom, Environmental Water Officer with the West Gippsland Catchment Management Authority, said monitoring over the last decade has provided valuable insight into the breeding behaviour of the Australian grayling in the Thomson system.

"This monitoring has uncovered spawning sites, showing that after a spawning event, Australian grayling eggs and larvae are found further downstream in the lower reaches of the Thomson system," Minna said.

"Most significantly, it has demonstrated the importance of well-timed and sufficiently long autumn freshes to trigger adult Australian grayling migration and subsequent spawning."

The findings have been used to refine environmental water releases in the Thomson and Macalister rivers, and monitoring over the past three years has shown successful breeding responses.

"The Australian grayling also wasn't the only species to benefit from the autumn freshes with avid canoers and kayakers taking advantage of the increased flows and travelling down the river on the weekend the water was delivered," Minna said.

Page last updated: 30/06/22