Record numbers of a critically endangered fish have been rediscovered in the River Murray following the successful delivery of environmental water.
Murray hardyhead is listed as critically endangered species with only a few known populations remaining in South Australia.
During the six-month monitoring program more than 75,000 individual Murray hardyhead were caught with almost 25,000 fish recorded during a single sampling event.
The monitoring program saw water levels raised at Lock 4 in conjunction with environmental watering of the Katarapko Floodplain near Loxton in the Riverland.
Minister for Environment and Water David Speirs said the monitoring program was made possible thanks to water for the environment provided by the Commonwealth Environmental Water Holder (CEWH) under the Murray-Darling Basin Plan.
“We know how important the delivery of environmental water is under the Murray-Darling Basin Plan and to have record numbers of critically-endangered fish rediscovered is a great result,” Minister Speirs said.
“Throughout the weir pool raising, the Marshall Liberal Government worked with our project partners to monitor the population of Murray hardyhead to see what influence the environmental watering event was having.
“We were blown away by the results. At the peak of the investigation our team caught a record number of Murray hardyhead with almost 25,000 fish recorded during a single sampling event and more than 75,000 individuals caught across the whole investigation.
“In recent months we’ve seen more action to deliver the Murray-Darling Basin Plan than ever before and projects like this show it is working and reconfirm why all Basin jurisdictions need to get on with delivering what’s been agreed for the health of the river and our communities which rely on it.”
Department for Environment and Water Project Manager Nathan Creeper said the weir pool raising and environmental watering of the Katarapko Floodplain provided important water flows into the Gurra Gurra wetland complex which is connected to the Lock 4 weir pool and home to the re-discovered population of Murray hardyhead.
“The monitoring has shown a really successful Murray hardyhead breeding response to weir pool raising,” Mr Creeper said.
“The Gurra Gurra Wetland Complex was heavily impacted by the millennium drought and reduced flows to South Australia and as a result has become more saline.
“The critically endangered Murray hardyhead have evolved to tolerate saline ecosystems and are now only found in these saline environments where they have a competitive advantage over other fish (pest and native fish species) that are less able to survive at high salinities.
“Through this thorough investigation and successful response, the links between the Murray hardyhead breeding and weir pool raising will inform future management of the population in coordination with weir pool manipulation.
“With floodplain watering at Katarapko planned for 2021 we are planning a potential raising of Lock 4 between July to December.
“We want to see Murray hardyhead populations continue to thrive and respond positively to the planned events and hope to build on this year’s successful outcome.”
The investigation and monitoring of Murray hardyhead was undertaken by DEW in partnership with the Murraylands and Riverland Landscape Board Wetlands team and Aqua-Save Nature Glenelg Trust and supported by the Commonwealth Environment Water Holder, Nature Foundation and Berri Barmera Landcare.