Abstract

The reproductive biology of Cherax cainii was studied in an impoundment dam in south-western Australia using histological examination of ovarian development (previous studies describing the reproductive biology of freshwater crayfish have relied solely on macroscopic descriptions of gonadal development). Spawning occurred between August and November and peaked in late August and September, with the percentage of berried females increasing from 50% in September to 96% in November before declining to 11% in December. Juveniles were released from berried females between late November and early December. Female gonads recovered dramatically after spawning with 81% of mature females possessing stage IV (maturing) gonads in March. The respective orbital carapace lengths at which 50 and 95% of C. cainii reached maturity were 32.1 and 37.9 mm for females, and 28.6 and 38.8 mm for males. The mean potential fecundity (i.e. number of mature ovarian oocytes prior to spawning) was 443 compared with 286 for the mean effective fecundity (i.e. number of pleopodal eggs, embryos or juveniles following spawning). The fact that the full ovarian reproductive potential of C. cainii is not attained is probably due to the limitation of egg attachment space on the pleopods.