A population model provides support for management decisions, enables ongoing research and reinforces strong partnerships to manage a threatened freshwater crayfish

Abstract

Many freshwater crayfish are threatened with extinction owing to varied threats such as urban development, pollution, over-harvest, and climate change, as well as invasive species. A recently published manuscript in Aquatic Conservation: Marine and Freshwater Ecosystems described a stochastic, age-based population model for the large freshwater crayfish Murray crayfish, Euastacus armatus, which is now threatened across much of its range in the Murray–Darling Basin in south-eastern Australia. The model was constructed for three regional populations using the best available knowledge of life-history traits such as longevity, size at onset of sexual maturity, fecundity, and survival, along with an account of density dependence. The model provides a framework to explore aspects of the conservation and management of the species, including assessing the influence of recreational harvest and environmental disturbance such as hypoxic blackwater, which affected the species significantly in 2010–2011. The application of the model provided retrospective justification for regulation amendments and highlighted biologically realistic timeframes for the recovery of impaired populations. This knowledge has assisted multi-jurisdictional fisheries management agencies to undertake routine reviews of fishery regulations, as well as to inform stakeholders of the benefits of the regulation amendments. Refinement of the modelling framework has already provided additional insight and it is anticipated that future application will help to address other important management questions. The modelling outcomes are at present informing conservation assessment of the species under the Australian Government's Environmental Protection and Biodiversity Conservation Act 1999. The benefit of the population model can be summarized as: providing a framework to inform and justify management decisions; enabling additional research; and guiding conservation assessment. This has strengthened strong partnerships (between ecologists, managers, and recreational fishers) required to manage the species effectively.