Reservoirs act as footholds for an invasive freshwater crayfish

Abstract

Understanding the modalities of aquatic species introductions is important in predicting and preventing new invasions. Australia’s Pilbara Province is an arid region with no naturally occurring freshwater crayfishes. We assessed the population demographics and reproductive potential of redclaw crayfish (Cherax quadricarinatus) in Lake Poongkaliyarra, a major Pilbara water supply reservoir, in which public access and fishing are prohibited. We found the population to have a high relative abundance with a range of size-cohorts present. The species was believed to have first been introduced into the reservoir from at least 2010 and has subsequently been introduced and established in other lotic systems in the region, probably through deliberate releases from the lake for the purposes of providing fishing opportunities to areas where public access is permitted. Introductions of C. quadricarinatus in other parts of Australia and the world have also initially established in reservoirs before subsequently colonising natural systems. The study highlights the potential for reservoirs to act as primary stepping stones for invasion by freshwater crayfish.