LIFE HISTORY AND REPRODUCTIVE BIOLOGY OF THE GILGIE, CHERAX QUINQUECARINATUS, A FRESHWATER CRAYFISH ENDEMIC TO SOUTHWESTERN AUSTRALIA

The gilgie, Cherax quinquecarinatus, a freshwater crayfish endemic to southwestern Western Australia, occupies a wide range of permanent and temporary aquatic environments. Reproductive and population biology parameters were determined in Bull Creek, southwestern Western Australia. Crayfish were collected monthly from May 2002 to April 2003. The seasonal von Bertalanffy growth curve, fitted for the first 14 months of life for female and male C. quinquecarinatus, had respective curvature parameters (K) and asymptotic orbital carapace lengths OCL∞ (CL∞) of 0.29 and 59.6 (71.2) mm for females and 0.25 and 73.8 (87.0) mm for males, respectively. This equates to OCLs (CLs) of females and males at age 12 months of 14.7 (19.2) and 14.1 (18.4) mm, respectively. Cherax quinquecarinatus was found to mature at a relatively small size, with the length at which 50% of individuals mature L50 for females and males being 18.8 and 24.5 mm OCL (24.1 and 30.9 mm CL), respectively. The majority of C. quinquecarinatus thus first spawned at the end of their second year of life. The potential (ovarian) and pleopodal fecundities of C. quinquecarinatus were relatively low compared to other freshwater crayfish species of similar size, being 81.7 (± 5.93 S.E.) and 77.1 (± 13.76 S.E.), respectively. Cherax quinquecarinatus underwent an extended spawning period, from late winter to late summer (i.e., August to February), with three spawning events facilitated by short brood and rapid gonadal recovery periods, traits consistent with other crayfish species able to exist in temporary environments. Estimates of total mortality (Z) were relatively high at 2.34 and 1.95/year based on age-converted catch curves for females and males, respectively, with a considerable proportion of this attributed to fishing mortality (exploitation rates of 0.76 and 0.75 for females and males, respectively). Cherax quinquecarinatus underwent a life-history strategy that showed characteristics of both a summer (r- strategist) and winter (K-strategist) brooder.