North Central Catchment Management Authority Native Fish Recovery Plan project manager Peter Rose said the flooding had created environmental challenges such as eroding riverbanks, deposition of silt, as well as increased carp populations.
“One of the main environmental impacts of the floods was water quality,” Dr Rose said.
“The scale of the flooding meant water ran out onto floodplains, further than it had for decades and following a wet season where a lot of crops were doing really well.
“Consequently, a lot of organic matter and nutrients washed into the river system, causing hypoxic black water, which resulted in some fish deaths.”
Fish deaths were reported across northern Victoria including at Kangaroo Lake, between Swan Hill and Kerang and in the lower Broken Creek.
Victorian Environmental Water Holder co-CEO Beth Ashworth said the VEWH had been able to work with Goulburn-Murray Water and various catchment management authorities to minimise fish deaths following the floods.
“Once we weren’t going to impact on towns or farms, we were able to work with G-MW and the CMAs to do some small releases and oxygenate the water,” she said.
“In smaller systems like the Lower Broken Creek, we were able to release fresh water into the systems and protect native fish.”
She said environmental flows were used outside of flood events to support native fish.
“We work really closely with G-MW and CMAs to release water through the irrigation district to key wetlands,” Ms Ashworth said.
“We tend to have big breeding events of native fish at particular locations throughout the southern Murray-Darling Basin.
“Using water for the environment, we can deliver flows to help move those juvenile fish throughout the southern Murray-Darling Basin to high-quality habitats.
“Murray cod and golden perch are natural predators to carp, so ensuring the native species thrive also helps mitigate the carp boom.”
Fishways also help as they allow fish to bypass man-made barriers such as weirs and dams.
Fishways have recently been constructed at Tea Garden Weir on the Ovens River, at Koondrook and Cohuna weirs on Gunbower Creek, and a further one is being constructed at Taylors Creek, to provide connectivity from Loddon River through to the Gunbower system.
Dr Rose said fishways had a significant impact on native fish populations.
“It is crucial we improve connectivity to help native fish thrive,” he said.
“The recently constructed fishways at Cohuna and Koondrook have allowed golden perch and Murray cod to move freely between the Murray River and 140km of Gunbower Creek.
“These fishways are a great success story, and it is the partnerships with G-MW and the VEWH that have enabled us to complete these large scale infrastructure projects.”
Learn more, by listening to the latest episode of Talking Water with G-MW at: www.g-mwater.com.au/podcast
