South Australia’s Katfish Reach is a diverse floodplain, home to at least 20 threatened species. The floodplain is large, covering around 9000 hectares. The reach is part of an anabranch system, where branches of waterways leave the main river and eventually join back up again, creating ‘spider webs’ of waterways across the floodplain.
The Katfish Reach is significantly affected by river regulation and the disposal of irrigation drainage water. Due to the effects of these, the biodiversity rating was poor, with widespread decline in the health of riparian vegetation and low numbers of large-bodied native fish.
In the past decade at the Katarapko-Eckert Creek Native Fish Demonstration Reach (also known as ‘Katfish’ Reach) in the lower Murray River, there have been significant restoration works, such as structure upgrades, barrier removals and fishway construction with the aim of increasing flow and improving connectivity through the Katarapko Anabranch system.
The primary ecological objective of these restoration projects is to improve the habitats that are favoured by large-bodied native fishes, including Murray cod (Maccullochella peelii) and Silver perch (Bidyanus bidyanus). These habitats need to be ‘lotic’, which means they must have permanent flowing water to support large native fish species.
In April 2021, the South Australian Research and Development Institute (SARDI) undertook an electrofishing survey within the Katfish Reach, jointly funded by the MDBA and the SA Department for Environment and Water. Over 9000 fish were sampled from 14 species.
The survey had encouraging results, particularly with the detection of Murray cod in Eckert Creek for the first time since surveys commenced in the region in 2009. The continued presence of Freshwater catfish (Tandanus tandanus) is also promising, as it indicates the riparian conditions are not further deteriorating. Further analysis and a comparison with previous monitoring data will be undertaken in the near future. The results of the analysis will be able to inform conservation and management projects for the Murray cod and catfish in the area.
This monitoring suggests encouraging early signs of ecological response to the restoration actions undertaken within the Katfish Reach. It is hoped that the removal of barriers to flow and fish, the installation of fishways and increased base water flows will continue to see improvements in large-bodied native fish populations in the system.
Other restoration works in the reach have included replacement of major in-stream barriers with new hydrological structures, installation of fishways, construction of erosion control and flood protection works. These works are hoped to further support the return of Murray cod to the Katfish Reach and its branches and wetlands.
Authors: Benita Dillon (DEW) and Chris Bice (SARDI)
Featured image: Katarapko creek. Photo credit: Bill Doyle