Plasticity in population biology of Cherax cainii (Decapoda: Parastacidae) inhabiting lentic and lotic environments in south-western Australia: Implications for the sustainable management of the recreational fishery

Abstract

The Smooth Marron Cherax cainii is endemic to south-western Australia and supports an iconic recreational fishery that exploits stocks in both lentic and lotic systems. This study is the first to determine and compare the population biology of a parastacid from both lentic and lotic systems and aimed to gather the information necessary for more effective management of the fishery. Modal progression demonstrated growth rates of juvenile C. cainii were greater in the lentic (Wellington Dam) compared to the lotic (Warren River) system, however, mark-recapture suggested the growth rate of the adult component of the lentic population was stunted whereas in the lotic population 60–90 mm OCL individuals were common and had a faster growth rate. The Wellington Dam stock appeared to be over-exploited and had very low productivity whereas the Warren River stock had relatively low fishing exploitation and a high productivity resulting from higher growth rates coupled with higher population densities (with the trappable population sizes estimated using the open POPAN formulation in the MARK software program). Comparisons of these biological parameters were made with populations elsewhere and there existed a considerable plasticity that is probably due to differences in thermal regimes, degree of habitat complexity, food resource availability and fisher accessibility. The findings demonstrate the need to determine the level of intraspecific biological plasticity in freshwater crayfish in order to sustainably manage their fisheries.