Successful artificial incubation and juvenile-rearing of dropped eggs of a critically endangered freshwater crayfish (Cherax tenuimanus)

One-third of the world’s freshwater crayfish species face extinction risk, necessitating extreme and urgent conservation measures such as captive rearing. Little information exists on these measures for most threatened species. The hairy marron, Cherax tenuimanus (Parastacidae), is a critically endangered freshwater crayfish endemic to the Margaret River in south-western Western Australia. C. tenuimanus is being rapidly replaced by the smooth marron, Cherax cainii, a translocated congener, causing its progressive decline in range, and now it faces imminent extinction in the wild. Attempts at captive breeding have resulted in few occurrences of egg laying of C. tenuimanus, which ended in complete loss of the clutch as eggs were progressively dropped by the female. To assess the potential of dropped eggs in captive rearing, we trialled ex situ artificial incubation techniques by using eggs dropped from a captively held female. Of 41 dropped eggs, 85% were successfully hatched in suspension upwellers, and 74% of the subsequent juveniles were reared successfully for 111 days in a purpose-built recirculating aquaculture system. We describe our protocols and facilities in detail because captive rearing of dropped eggs was demonstrated to be a viable option for improved success of captive reproduction. These approaches may be applicable for conserving similar crayfish species.