Murray hardyhead (Craterocephalus fluviatilis) is a threatened, small (<100 mm) freshwater fish, endemic to the lower Murray-Darling River Basin in South Australia, Victoria and New South Wales, that lives for a maximum of 18 months. Over the past 50 years, the species has suffered a severe decline in range and abundance.

In Victoria, the small number of remnant populations of Murray hardyhead are located in saline habitats. Recent surveys of these populations demonstrate the species is on the verge of extinction in Victoria, with Murray hardyhead captured at only three out of six known sites in the State. Due to its decline, Murray hardyhead is now one of the most threatened fish species in Australia. Decline of the species, at least in part, is suspected to be a consequence of the presence of salinities which conflict with the breeding ecology and survivorship of early life stages.

The Victorian government funded a program in 2018, managed by Dan Stoessel of the Arthur Rylah Institute, which aimed to reduce the uncertainty around the salinity tolerance of early life stages. The outcomes of the program were expected to guide watering of saline wetlands containing the species to promote egg, larvae and juvenile survivorship, and therefore the long-term survival of the species.

Aquaria used to determine the salinity tolerance of early life stages of Murray hardyhead.  Photo: Dan Stoessel

The program has been a great success, not only indicating that eggs of the species are less tolerant to salinity than later life stages (i.e. larvae, juveniles and adults), but also identifying when best to deliver water to sites. To test the outcomes of the project, two lakes in the Kerang area which are known to have Murray hardyhead present, were watered based on the project findings. Recent monitoring of the sites indicated that the fish are present in large numbers at both sites, to an extent which has not been observed for at least 10 years. An additional outcome of the project is that we also now have the know how to produce large numbers of individuals in captivity (funding dependent) for release to the wild to reverse the decline of the species.

Adult Murray hardyhead captured from Round Lake, May 2019.  Photo: Dan Stoessel
Murray hardyhead in fyke net.  Photo: Dan Stoessel

This work has been a strong collaboration between DELWP ARI, the North Central Catchment Management Authority and the Victorian Environmental Water Holder. The monitoring is part of the WetMAP (Victoria’s Wetland Monitoring and Assessment Program for environmental water).

Floodplain specialist fish forum:
Bringing back ‘The Magnificent Six’

A forum was held in Bendigo to bring together experts and waterway practitioners to share the latest information and management approaches being used to address the plight of the Magnificent Six.

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