Production of juvenile redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae) I. Development of hatchery and nursery procedures

Procedures were developed for the controlled production of juvenile redclaw crayfish, Cherax quadricarinatus in tanks over two seasons. These included broodstock handling methods and involved the definition of an in vivo ovary staging technique which permitted recognition of immature, maturing and mature females. Hatchery techniques were also defined which demonstrated that male:female ratios of up to 1:4 were equivalent for successful mating and spawning. Up to 97% of females spawned and carried eggs through to hatching when held in tanks at between 24.5 and 27.6 °C mean daily temperature and exposed to 14:10 hours light:dark day length. A sequential series of seven egg stages was defined from egg release through to hatching, based on morphological characteristics. The mean duration of each stage was measured and cumulative statistics calculated, indicating a mean incubatory period of 72.1 days (range 47 to 84) and 66.3 days (56 to 71), respectively, for the two hatchery runs. An exponential function was calculated which defines the relationship of fecundity and female size and which indicates that fecundity ranges from approximately 200 to 1000 eggs per female. Nursery procedures were developed which indicate difficulties with using the floating water plant Pistia as juvenile habitat, and the benefits of using artificial shelters. Newly hatched juveniles stocked at between 980 and 1842 m2, and fed a combination of formulated flake food and fresh zooplankton, survived well (mean 52%) and increased in size by between 500 and 900% over 28 to 50 days. The research demonstrates that C. quadricarinatus can be easily bred in captivity and juveniles reared successfully with relatively simple facilities and techniques.