Murray hardyhead conservation case study
|Full title||Murray hardyhead translocation from the South Australian Riverland to Brickworks Billabong in the Victorian Mallee.|
|Contact Person||Iain Ellis|
|Funding Body||Mallee Catchment Management Authority|
|Duration||February to April 2015, with ongoing monitoring to be confirmed|
|Collaborators||Victorian Department of Environment, Land, Water & Planning (DELWP Regional Services and the Arthur Rylah Institute), South Australian Department of Environment, Water and Natural Resources (DEWNR), Mallee Catchment Management Authority (MCMA), Commonwealth Environmental Water Office (CEWO), Parks Victoria, Victorian Environmental Water Holder|
Murray hardyhead (Craterocephalus fluviatilis) are small-bodied native fish endemic to the lowland floodplains of the Murray and Murrumbidgee River systems. The species was historically common throughout South Australia, southern New South Wales and northern Victoria, having been collected as far upstream as Yarrawonga and as far downstream as Lake Alexandrina at the mouth of the Murray. The range of Murray hardyhead has declined drastically over recent years, largely due to the effects of drought and human processes which impact on water quality, isolation of wetlands from the river and competition or predation from introduced fish species like Mosquito fish and Redfin perch. Remnant Murray hardyhead populations are generally located within saline habitats, possibly due to the species being an efficient osmoregulator at high salinity (Wedderburn et al. 2008). The species is listed as endangered or critically endangered at both the state and national (EPBC) level in Australia, and also on the International Union for the Conservation of Nature Red List of Threatened Species.
A revised Recovery Plan has been completed recently by DELWP and will soon be submitted to the Australian Government Department of the Environment (DotE). Key recovery objectives are to (1) protect, maintain and monitor known populations, and (2) increase the area of occupancy of the species. One method of increasing the area of occupancy is to translocate fish from existing populations to carefully selected and prepared floodplain sites, from which natural dispersal will be possible in future flood events.
In particular, increasing the number of Murray hardyhead populations via translocation of fish from existing, primary populations during non-crisis periods would decrease the likelihood of extinction in future critical circumstances by spreading risk (Ellis et al. 2013). Translocation to suitable floodplain wetlands which are close to water sources (thus facilitating easy delivery of environmental water) can establish new, secondary populations. These translocated populations may act as dispersal nodes during future flood connectivity, thereby improving the chances for species recovery. However, when sourcing fish for translocation care must be taken to ensure the removal of fish does not infer significant deleterious impacts on the donor populations.
Monitoring of trends for both primary and secondary populations is also essential to the recovery of the species in order to identify future declines, and inform our ability to adopt responsive management strategies.
Case study: successful collaboration enables interstate translocation
Disher Creek and Berri Evaporation Basin form part of a Murray River wetland system used for saline water disposal near Berri, in the Riverland region of South Australia. In recent decades, Murray hardyhead in this system were largely confined to a small (less than 1 ha) drainage outfall pond in Disher Creek and a similar sized section of creek adjacent to Berri Evaporation Basin. Regulatory structures and on-ground works were coordinated in 2009 by DEWNR to increase available habitat by controlled diversion of environmental water (from the River Murray) and saline groundwater to the site (Suitor 2009). Despite these efforts, drought induced critical water shortages threatened the viability of both populations in 2009 and Murray hardyhead were salvaged for captive maintenance at MDFRC facilities in Mildura. Disher Creek and Berri Evaporation Basin re-connected to the Murray River during flooding in 2010 and following subsequent disconnection, remaining captive bred Murray hardyhead were returned to the sites in 2012.
Monitoring of both Riverland populations of Murray hardyhead in February 2015 identified strong abundances, which are likely to reflect a positive response to the conservation efforts by the DEWNR, using water supplied by the Commonwealth Environmental Water Office. This promising monitoring result presented an ideal opportunity for collection of a sub-population of Murray hardyhead from these sites to relocate into an appropriately prepared wetland.
Fortunately, a long collaboration between DELWP, MDFRC, and MCMA has created suitable translocation sites including Brickworks Billabong, a location just a few hundred kilometres from Disher Creek near Mildura in Victoria. Brickworks Billabong is located within the proposed Murray River Park and is managed for conservation by Parks Victoria. Environmental water was delivered to Brickworks Billabong in 2013 specifically to create a future translocation site for Murray hardyhead, with additional environmental water allocated as required to help establish suitable habitat. The site provides habitat which is uniquely important for the species, in that it exhibits elevated salinity and therefore few aquatic predators and competitors.
In response to the strong monitoring result in the Riverland, MDFRC facilitated a rapid response from both Victorian and South Australian state departments to fast track approval for the translocation of Murray hardyhead. Meanwhile, MDFRC requested that the MCMA and CEWO concurrently provided an addition of environmental water to Brickworks Billabong in early March 2015 in order to increase available habitat, and prompt a production boom in the wetland, thus enhancing food supply in readiness for the addition of Murray hardyhead from the Riverland populations.
Once translocation approvals were obtained, staff at MDFRC and DEWNR moved swiftly into action to capture and relocate a sub-population of Murray hardyhead from the Riverland to Brickworks Billabong. In early March 2015 sampling nets in Disher Creek and Berri Evaporation Basin collected approximately 2500 Murray hardyhead. These fish were carefully transferred into an oxygenated water-holding trailer, designed specifically for the transportation of live fish, and generously provided by DELWP.
Upon arrival at Brickworks Billabong, in the customised trailer, the fish were ‘soft-released’ after a process of acclimatisation to minimise the potential for transfer shock (due to temperature or water quality difference between source and receiving water). Upon release, the thousands of fish dispersed quickly into their new home, showing no obvious effects from the cross-border road trip. Monitoring events conducted in late July detected juvenile Murray hardyhead in Brickworks Billabong. Estimated to be 2-3 months old, these juveniles demostrates successful breeding by relocated fish following the translocation - hopefully this indicates development towards a thriving new population in the Mallee. Ideally a long-term monitoring strategy will document future success in terms of successive breeding within the newly established Brickworks Billabong Murray hardyhead population.
To the best of our knowledge this is the first official interstate translocation of threatened fish between South Australia and Victoria. The Murray hardyhead Recovery Team, initiated by the MDFRC, and driven by MDFRC and DELWP is at the centre of a well-established collaborative network formed during a decade of conservation programs which has enabled this cross-border translocation process to be completed in a matter of weeks. The combined team effort involved in this recovery action serves as a model for facilitating cross-jurisdictional collaboration in the conservation of threatened fishes. The ability to act swiftly to take advantage of windfall situations (like the population boom detected in Disher Creek) is a key quality that all threatened species managers and researchers should be striving for. The collaboration involving states and departments which has formed to coordinate strategic conservation actions for this species in the last decade is a blue print for success in the field of freshwater fish conservation, and is paving a path for the streamlining of threatened freshwater fish recovery processes.
Suitor L (2009) Disher Creek Saline Water Disposal Basin Hydrological Management Plan. Department for Environment and Heritage: Berri, SA.
Ellis I, Stoessel D, Hammer M, Wedderburn S, Suitor L and Hall A (2013) Conservation of an inauspicious endangered freshwater fish, Murray hardyhead (Craterocephalus fluviatilis), during drought and competing water demands in the Murray–Darling Basin, Australia Marine and Freshwater Research 64(9) 792 - 806
Wedderburn SD and Walker KF (2008)Osmoregulation in populations of an endangered hardyhead (Atherinidae:Craterocephalus fluviatilis McCulloch, 1912) from different salinity regimes. Ecology Freshwater Fish 17, 653–658.