Murray crayfish
The Murray crayfish is the world’s second largest freshwater crayfish and after 40 years, has returned to South Australian waters!
Murray crayfish naturally occurred across the entire catchment of the Murray and Murrumbidgee river systems in the southern Murray-Darling Basin, however the species has undergone significant declines in distribution and abundance over the past 50 years. Although still quite common in the upper river systems, it is much harder to find downstream of Echuca and has been considered extinct in South Australia since the 1980s.
Murray crayfish can weigh up to 2 kg; however, they are slow-growing and can take up to 9 years to reach full maturity. Like all other freshwater crayfish species, they go through a series of moults as they grow. Feeding on decaying animals and plants, Murray crayfish are opportunistic feeders.
Preferring cooler and well aerated water with plenty of woody habitat, they become more active during the winter months with mating usually occurring in May, likely due to a drop in water temperatures.
Females carry up to 2,500 eggs under their tails, attached to their pleopods (small limbs under the abdomen). Eggs hatch during late spring, approximately 140 days after fertilisation. Juveniles will stay attached to the mothers pleopods for a short time until they have gone through a series of moults, then become self-sufficient.
Why are Murray crayfish threatened?
- River regulation – causing change in water flow, temperature, etc
- Habitat change – removal of snags to improve boating access
- Sediment can fill deep pools, cover shelter, and bury the banks Murray crayfish need for burrowing
- A history of overfishing – both commercial and recreational
- Pollution and pesticide run off into rivers
- Extreme weather events such as flooding can create blackwater events which can be devastating to a population
- Local populations may not recover naturally because Murray crayfish can’t travel long distances to recolonise areas
What is being done to help the Murray crayfish?
In 2023, Murray crayfish were re-introduced into South Australia as part of a trial to see if the species can be successfully re-established in the River Murray in South Australia. Each year, approximately 200 adult crayfish are translocated from healthy upstream population sites and around 400-500 juveniles, raised in captivity, are released into the reintroduction reach in the Riverland, South Australia.
This five-year reintroduction project is a collaboration between the Murraylands and Riverland Landscape Board and the Nature Glenelg Trust, with the valuable support of NSW Fisheries and the River Murray and Mallee Aboriginal Corporation. It is kicking many goals for the conservation effort for this EPBC listed species.
To find out more here, or head to the Nature Glenelg Trust website.
Help save the Murray crayfish
Murray crayfish are fully protected in South Australia. If you accidentally capture a Murray crayfish, please take a photo and put the animal straight back into the water. Nature Glenelg Trust are keen to hear of any reported sightings. Please email them and include any pictures.
Adult Murray crayfish are easier to identify by their big white claws and spines; however, juveniles are similar to yabby juveniles. So, if you see a juvenile looking crayfish with a wider body (carapace) and shorter tail than a yabby, please take a picture and send to Nature Glenelg Trust for identification.