Genetic assessments are critical for the management and conservation of wild populations. I evaluated genetic changes in populations of western rock lobster, Panulirus cygnus, and of hairy marron crayfish, Cherax tenuimanus. I found no evidence of declines in genetic diversity in P. cygnus, despite heavy exploitation and the impact of environmental factors. Furthermore, no impact of selective exploitation on the mating system of P. cygnus was observed, although reduction in body size was observed in exploited sites. In the case of C. tenuimanus, the low proportion of individuals remaining has shift conservation efforts towards the establishment of ark sites.