There are currently 38 described species of native freshwater crayfish known in Victoria, all within the Parastacidae family. These include yabbies (Cherax species), spiny crayfish (Euastacus species), burrowing crayfish (Engaeus species), bush yabbies (Geocharax species) and one swamp yabby speices (Gramastacus species). Around half of these species are threatened in the state, often having restricted distributions, specialised habitat needs and characteristics which make them vulnerable (e.g. slow growth, long-lives, late maturity). There is also a West Australian species, Smooth Marron (Cherax cainii), which was introduced to Victoria and is a declared noxious species.
For many years, ARI has been involved in research and monitoring to support freshwater crayfish conservation. This has included identifying new species; determining their distribution and abundance; assessing the impacts of threats and their status; undertaking actions to protect and restore populations; and providing advice on their conservation, including after bushfires and floods.
Understanding diversity of freshwater crayfish
Understanding the diversity of freshwater crayfish is key to their effective management. It underpins knowledge of their distribution and the diversity of species across Victorian habitats, helps clarify their conservation status and provides insights about threats and management needs.
In 2021, a new species of freshwater crayfish, the Swamp Yabby (Cherax latimanus) was formally described, by scientists at ARI and a private research group Australian Aquatic Biological. This was the first time in 80 years that a new yabby
species in the Murray-Darling Basin system has been recognised, making the Swamp Yabby only the third Cherax species known to naturally occur in the Basin. This species has often been mistaken for the Common Yabby (Cherax destructor) in the past.
Current research has identified at least four new species of spiny crayfish in the Gippsland region and two new species of bush yabbiesin western Victoria, and these are in the process of being formally described.
ARI has also developed expert identification skills for burrowing crayfish (Engaeus), the most challenging crayfish group to identify correctly due to the similarity between species and the numerous, small taxonomic characteristics. We are now relied upon extensively for this knowledge by other researchers.
Understanding distribution and abundance
Over the last 20 years, ARI has led crayfish surveys and monitoring in many regional and state-wide programs. These include Regional Forest Agreement surveys; the National Estate program; Biodiversity Response Plans; the Forest Protection Survey Project; the Landscape Scale Biodiversity Project; and the Bushfire Recovery Program. Our enhanced understanding of the distribution and abundance of crayfish species has been critical in the protection of these animals, in both state and national contexts.
Recent highlights include:
- undertaking the population and distribution assessment of Mallacoota Burrowing Crayfish (Engaeus mallacoota)
- confirming the on-going presence of the Curve-tail Burrowing Crayfish (Engaeus curvisuturus) in the upper Yarra catchment for the first time since the species was described in 1990
- distributional surveys for many threatened spiny crayfish in East Gippsland
- trialling the collection and analysis of DNA in water samples for the remote detection of the species in the wild
Crayfish are also monitored as part of the Murray Darling Basin Authority’s long-term monitoring program (The Living Murray initiative) at Icon Sites including the Barmah-Millewa Forest. ARI has regularly been involved in this monitoring.
Assessing and managing threats
The Dandenong Burrowing Crayfish (Engaeus urostrictus) is a threatened species with a restricted distribution within the rare forest type of Cool Temperate Rainforest. ARI has surveyed for this species using novel survey techniques and has provided expert advice on its conservation. Protection of the species’ habitat includes a collaboration between DEECA and the Yarra Ranges Council with support from the Community Weed Alliance of the Dandenongs, Melbourne Water, Parks Victoria and other community groups.
Murray Crayfish (Euastacus armatus), a threatened species popular in recreational fishing, has experienced recent declines in distribution and abundance. It is a long-lived species (+25 years), and vulnerable to overfishing and hypoxic ‘blackwater’ events during flooding which result in extremely low levels of oxygen in the water. ARI has undertaken population modelling for this species to examine the risk of harvest pressure and blackwater events, and provide management advice.
Emergency management and extreme events
Following the Victorian bushfires over the summer of 2019/20, ARI was involved in many actions to protect aquatic species, including providing expert advice on appropriate actions, reconnaissance of priority species and sites, and emergency translocations. This work also included the temporary extraction and housing of three threatened crayfish within the ARI aquarium (East Gippsland Spiny Crayfish (Euastacus bidawalus), Orbost Spiny Crayfish (Euastacus diversus), Arte Spiny Crayfish).
Following the large-scale floods in northern Victoria in 2022, surveys are underway on the status of Murray Crayfish in the Barmah-Millewa Forest, in collaboration with Yorta Yorta Nation Aboriginal Corporation. ARI also undertook an impact assessment for the Mallacoota Burrowing Crayfish following floods in July 2022.
Implementing recovery actions
There are several projects underway to improve the status of freshwater crayfish. These include:
- the 10inTen plan to restock and recover threatened species; the South Gippsland Spiny Crayfish (Euastacus neodiversus), a species which was affected by storm damage in recent years, will be the focus of captive breeding trials to fill key knowledge gaps
- the Ovens River Demonstration Reach program, a long-term integrated river rehabilitation effort with field surveys and community based engagement and education around a variety of species, including Murray Crayfish
- an assessment of habitat conditions at potential crayfish reintroduction sites, and translocation strategies for Murray Crayfish in Little Murray River, in collaboration with the Wamba Wamba traditional owners and the North Central Catchment Management Authority
For further information contact: Tarmo.Raadik@delwp.vic.gov.au or Scott.Raymond@delwp.vic.gov.au
Page last updated: 28/10/24