Victoria’s zombie fish are back from the dead, and there are plans underway to return the species to its former range throughout the Murray Corridor.
But first, let’s meet this zombie fish! The southern purple-spotted gudgeon (Mogurnda adspersa – pictured above) is a small, colourful, and native floodplain specialist fish. Once widespread in wetlands, lakes, billabongs, and slow-flowing river habitats, by the 1970s, the species had all but disappeared from the southern Murray Darling Basin. The decline is likely due to a range of factors including altered flows and loss of permanent floodplain wetlands, poor water quality and habitat, and competition with, and predation by, alien fish species. Before the turn of the 21st century, they were considered extinct in the wild in Victoria, with the last record being from the Cardross lakes in 1998.
In late 2019, two of them were captured during a survey of Third Reedy Lake near Kerang in northern Victoria, as part of a plan to generate water savings for the environment. After the discovery, the Southern Purple-Spotted Gudgeon Advisory Group was set up with representatives and experts from the Department of Environment, Land, Water, and Planning, North Central Catchment Management Authority (CMA), Arthur Rylah Institute, Connections, Goulburn Murray Water, Parks Victoria, the Victorian Environmental Water Holder, and environmental services company Austral Research and Consulting. The group was tasked with developing a plan that worked towards the long-term survival of the species, while enabling the reinstatement of Third Reedy Lake to a more natural state.
The drawdown (lowering the water level) of Third Reedy Lake was put on hold, water for the environment was delivered to keep the water level stable, and fieldwork commenced to investigate the distribution and abundance of fish in Third Reedy and other nearby waterways. This included sampling using fyke nets and bait traps, and collection of eDNA samples at about 70 sites throughout the lower Loddon catchment, including the Kerang lakes.
More southern purple gudgeon was soon discovered at Third Reedy Lake, three were found at Kangaroo Lake, eight at Racecourse Lake and 66 at Middle Reedy Lake, next door to the original find.
Another group of ‘zombie fish enthusiasts’, including North Central CMA staff, Austral Research and Consulting, Native Fish Australia and Australia New Guinea Fishes Association worked to secure the species by starting a captive breeding program and creating insurance populations through the creation of surrogate habitats. This work was funded through a Department of Environment, Land, Water and Planning Icon Species grant.
The group collected 30 broodstock from Third and Middle Reedy lakes, and breeding commenced with specialist breeders at Middle Creek Farm and Aquasave. The breeding program has been successful, with the production of over 1000 juvenile fish, expected to be ready for release by the end of 2021.
Fin clips taken from the Kerang population are currently being analysed, and this will help inform future breeding and release plans. As an example, these plans may include mixing fish with individuals from South Australia to improve genetic diversity.
Meanwhile, North Central CMA’s ‘Working for Victoria’ crews, City of Greater Bendigo Council and landholders have been busily preparing potential release sites, by planting aquatic and riparian vegetation and installing woody habitat.
Final assessment and selection of 2-3 local reintroduction sites will occur over the coming months, with baby zombies due to be released in November 2021, and follow-up monitoring of their establishment shortly thereafter.
The Mid-Murray Recovery Reach Program, established as part of the MDB Native Fish Recovery Strategy, aims to recover floodplain specialist fish in the Murray Corridor. The Program will continue to fund the breeding program, and prepare and maintain additional surrogate sites, such as the Deniliquin Lagoons, which have been earmarked for reintroduction of the zombie fish in 2022.
Featured image: Southern purple-spotted gudgeon. Photo credit: Doug Gimesy.
Mid-Murray Floodplain Recovery Reach
This 400+km network of permanent waterways, ephemeral creeks, and wetlands, has one of the highest diversities of native fish species within the Murray-Darling Basin.