The Murray crayfish (Euastacus armatus) is a large iconic freshwater species that is the basis of popular recreational fisheries in many areas of the southern Murray-Darling Basin. Despite the social importance of Murray crayfish, little information has been formally published about the species. The majority of data are only available as unpublished departmental manuscripts, theses, secondary references to unpublished data, or in items published outside of peer-reviewed scientific journals. Consequently, the information that is available about Murray crayfish is difficult to access.
Anecdotal reports by rural community members and recreational fishers indicated that Murray crayfish populations had declined in distribution and abundance over the last 50 – 60 years. However, the lack of scientific data regarding its status and biology of this species, and the impacts of potential threatening processes, had limited the ability to validate reported declines and develop successful management strategies. This report reviewed and assimilated all available information on Murray crayfish (both published and accessible unpublished material), and identified key knowledge gaps relevant to sustainable management of the species.
The report summarised knowledge of the ecology, distribution and management of the species. Ecological knowledge included summarised species description; taxonomy; systematics; historical and current distribution; population genetics; anatomy and sense perception; habitat use and requirements; environmental tolerances; diet; movement, migration and diel activity; diseases and parasites; reproduction and recruitment; age and growth; size at maturity; mortality; population structure; sex ratios; historical and current abundance and ecological role.
Management knowledge summarised within the report includes historical translocations in NSW; commercial and recreational fisheries management; and aquaculture. A range of management recommendations are presented, including requirements for improved monitoring, controls on trade and movement, improved water allocation, community education approaches, improved habitat management and rehabilitation, promotion of interstate consistency of fishery regulations, increased enforcement capacity, and developing a collaborative management and conservation relationship with Aboriginal stakeholders.
Threats to the species are outlined including:
- River regulation
- Pesticides and pollution
- Habitat degradation
- Translocation of crayfish
- Thermal pollution
- Introduced fish species
- Fish passage
The traditional ecological knowledge, historical use and cultural significance to Aboriginal peoples are also described.
Implications for native fish
Murray crayfish have declined across most of its historical distribution in the MDB. The species is now considered extinct in South Australia, vulnerable in the ACT and threatened in Victoria. The species is not considered threatened in New South Wales (at the time the report was prepared). As a slow growing, late maturing, long-lived species, it is susceptible to overharvest. This means management regulations need to be regularly reviewed and updated as required.
Locally extinct populations in South Australia and the Murray River downstream of Mildura may be amenable to population reestablishment, and previous calls for a Murray crayfish re-introduction program in the lower Murray River are supported by this research. There is the potential to trial the re-establishment of Murray crayfish in flowing reaches of the lower Murray River. Subsequent monitoring of reintroduced populations would provide an opportunity to assess the criteria for population establishment and determine the timeframes required for populations to reach self-sustaining levels.
Gilligan, D., Rolls, R., Merrick, J., Lintermans, M., Duncan, P. and Kohen J. 2007. Scoping the knowledge requirements for Murray crayfish (Euastacus armatus). Final report to Murray-Darling Basin Commission for Project No. 05/1066. Fisheries Final Report Series No. 89. NSW Department of Primary Industries, Cronulla.
ACT Government, 1999. Murray River Crayfish (Euastacus armatus): A vulnerable species. Environment ACT, Canberra.
Asmus, M., 1999. Effects of Recreational Fishing on Populations of Murray Crayfish (Euastacus armatus) in the Murrumbidgee River. Charles Sturt University, Wagga Wagga.
Barker, J., 1992. The spiny freshwater crayfish monitoring program 1990 Victoria. Department of Conservation and Environment Fisheries Management, Victoria.
Geddes, M.C., Musgrove, R.J., Campbell, N.J.H., 1993. The feasibility of re-establishing the River Murray crayfish,( Euastacus armatus), in the lower River Murray. Freshwater Crayfish 9, 368-379.
Gehrke, P.C., 1992. Demography of Murray crayfish (Euastacus armatus) in the Murrumbidgee River at Narrandera. NSW Fisheries, Narrandera, NSW.
Lintermans, M., Rutzou, T., 1991. The status, distribution and management of the Murray crayfish Euastacus armatus in the Australian Capital Territory. ACT parks and Conservation Service, Canberra.
McCarthy, B., 2005. Distribution of Murray Crayfish (Euastacus armatus) in the Mallee Region 2004. Technical Report. Murray-Darling Freshwater Research Centre, Mildura.
Morison, S., 1988. Results of surveys of Murray River spiny crayfish – Euastacus armatus. Kaiela Fisheries Research Station, Fisheries Division, Department of Conservation, Forests and Lands, Victoria.
O’Connor, P., 1986. The biology of the Murray crayfish (Euastacus armatus) and recommendations for the future management of the fishery. NSW Fisheries, Narrandera, NSW.
Zukowski, S., Curtis, A., Watts, R., 2011. Using fisher local ecological knowledge to improve management: The Murray crayfish in Australia. Fisheries Research 110, 120-127.
Zukowski, S., Watts, R., Curtis, A., 2012. Linking biology to fishing regulations: Australia’s Murray crayfish (Euastacus armatus). Ecological Management and Restoration 13, 183-190.