Carp surge to record levels as native fish crash

The ‘just add more water’ strategy of the Albanese Government is failing, as reports show carp numbers hitting record levels as native fish populations crash.

Carp numbers have exploded. Generic picture: Daniel Truscott

The ‘just add more water’ strategy of the Albanese Government is failing, as the Murray Darling Basin Authority’s latest condition reports show carp numbers hitting record levels as native fish and waterbird populations crash.

The University of Adelaide Lower Lakes condition report, released this month, states: “Of the alien fish species, common carp had a massively higher abundance in March 2023 compared to March 2022, and indeed, any other year since condition monitoring began in 2007”.

In March 2022 researchers picked up 179 carp at 19 sites, prior to the floods later that year. But 12 months later that number had exploded to 38,111 at 21 sites.

“There is a high likelihood the extremely high abundance of young-of-the-year Common Carp in the Lower Lakes over summer and autumn 2023 impacted on the recruitment outcome of Southern Pygmy Perch, and many other native fish species, through competition for space and resources.”

The team found just one native Murray hardyhead in the lakes, which they said indicated “a continued decline at the condition monitoring sites”.

No Yarra pigmy perch were found, leading the team to conclude the species was now extinct in the Basin, and that populations of other small native species had slumped.

Another group of Adelaide University researchers found bird numbers had also plummeted, with “both the Coorong and the Lower Lakes failing to meet the long-term threshold ecological targets set for the abundances and distributions of 25 species in the Lower Lakes and 40 species in the Coorong in January-February 2023”.

“The resultant negative Whole of Icon Site Score (WOISS) for these two wetland systems were not only lower than in January-February 2022 but were the lowest recorded since the end of the Millennium Drought and the commencement of the Murray Darling Basin Plan”.

Federal Opposition water spokeswoman Perin Davey said the “just add water approach” had failed to solve the basin’s problems.

“These reports show we shouldn’t be embarking on additional large scale buybacks, until we better understand what does and doesn’t work”.

Asked why after 16 years the basin plan had failed to improve the condition of key icon sites, Federal Water Minister Tanya Plibersek’s bureaucrats stated the Basin Plan was “not fully implemented”: “Full implementation of the Basin Plan will ensure we have the best chance of achieving a healthy Basin.”

Yet even upstream of the Lower Lakes Victoria’s Arthur Rylah Institute researchers found the condition of native fish and crayfish populations in the Barmah-Millewa forest had slumped to record lows in 2022-23.

“The population indices received a D and E (rating) in flowing and semi-permanent habitats, respectively, the worst recorded since monitoring began,” the ARI team reported.

Drift net sampling of the Murray River within the forest picked up nine silver perch eggs, seven golden perch eggs and 3139 carp larvae.

A recent ARI research paper, which modelled the impacts of floods on carp populations, found “large natural floodplain inundations … maintained high carp biomasses and thus likely high impacts on natural ecological values.”