Key words: Murray Crayfish, crustacea, Murray-Darling Basin, knowledge gaps
Murray Crayfish (Euastacus armatus) is highly valued by recreational fishers in the southern Murray-Darling Basin, and is also listed as a threatened species across much of its range. Murray Crayfish is believed to have declined in distribution and abundance over the last 50-60 years. Because little of the research undertaken on the status, biology or potential threatening processes of this species has been published, it is difficult to validate the reported declines and develop successful management strategies. The majority of data are only available as unpublished departmental manuscripts, theses, secondary references to unpublished data, or in items published outside of peer-reviewed scientific journals.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.
Figure 1. Murray Crayfish are highly valued by recreational fishers, (Photo courtesy of Jamin Forbes)
Figure 2. As a slow growing, late maturing, long-lived species, Murray Crayfish are susceptible to overharvest. (Photo courtesy of Jamin Forbes)
Broad aim and methods: This project reviewed and assimilated all available information on Murray Crayfish (both published and accessible unpublished material sourced from electronic databases, unpublished reports and datasets and unpublished student theses). Key knowledge gaps relevant to sustainable management of the species were identified and recommendations provided.
Findings: The project summarised knowledge of the ecology, distribution and management of Murray Crayfish. Ecological knowledge summarised includes 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 presented includes historical translocations in NSW; commercial and recreational fisheries management; and aquaculture. This project provides a range of management recommendations including requirements for improved monitoring, controls on trade and movement, improved water allocation, a community education program, 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
- Overfishing
- Habitat degradation
- Translocation of crayfish
- Thermal pollution
- Introduced fish species
- Fish passage
The traditional ecological knowledge, historical use and cultural significance of Murray Crayfish to Aboriginal peoples were also characterised.
Lessons learned and future directions: Murray Crayfish has declined across most of its distribution, and is considered extinct in South Australia, vulnerable in the ACT and threatened in Victoria. The species was 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 and so it is important that management regulations are regularly reviewed and updated. 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 with 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.
Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy, and conducted by a collaborative team from NSW Department of Primary Industries, University of New England, Macquarie University, ACT Parks, Conservation and Lands, Murray-Darling Basin Commission and NSW Department of Environment and Conservation.
Contact: Dr Dean Gilligan Senior Research Scientist Freshwater, NSW Department of Primary Industries Level 1, Braysyth Building Cnr Beach Road & Orient Street Batemans Bay NSW 2536. Tel: +61 2 4478 9100. Email: dean.gilligan@dpi.nsw.gov.au.
Link:
EMR Project Summaries 