Cherax tenuimanus

Cherax tenuimanus, known as the Margaret River hairy marron, is a large freshwater crayfish belonging to the family Parastacidae. It is among the largest freshwater crayfish species in the world, distinguished by a robust, smooth carapace and, in males, noticeably hairy claws that give the species its common name. As a benthic omnivore, it feeds on decaying plant matter, algae, and small invertebrates, playing an important role in nutrient cycling and organic matter breakdown within river systems.

It is generally slow-growing and long-lived, traits that make its populations particularly vulnerable to overexploitation.

The species is endemic to Western Australia, historically restricted to the Margaret River and a small number of adjacent freshwater streams in the southwest of the state. It inhabits cool, well-oxygenated freshwater habitats, including river pools, riffles, and shaded stream sections with abundant woody debris and undercut banks for shelter.

Its decline stems from two ongoing pressures: unregulated and historical fishing and harvesting for food and recreation, which has directly reduced adult breeding populations, and logging and wood harvesting activities that degrade riparian vegetation, increase sedimentation, and raise water temperatures in its narrow habitat range. Its restricted distribution amplifies the impact of these pressures, leaving little scope for population redundancy.

Conservation responses include harvest restrictions, monitoring of remaining populations, and habitat protection measures within its native catchment, along with translocation and captive breeding efforts aimed at establishing insurance populations. Despite these actions, the species remains classified as Critically Endangered, with a continuing decreasing population trend. Its narrow geographic range and ongoing habitat pressures suggest that sustained management intervention will be necessary to prevent further decline.