Redclaw Crayfish

Reproductive Biology

Under a constant temperature (26–28°C) and either an ambient or a controlled (14L:10D) photoperiod. A similar annual pattern of spawning and molting was evident under the two photoperiod regimes. Females spawned three times and moulted twice a year on average. Most spawning occurred during spring and summer, and moulting occurred mainly after the breeding season but also between spawns.

Male and female redclaw can be easily distinguished by the presence of the red patch on the chelae of males. Life span is 4-5 years based on maximum size recorded of around 650 g. Sexual maturity is reached at 6-12 months with a body weight of approximately 110-120 g. Male specimens are fully grown at two years when they reach the weight of about 400 g. In Queensland, redclaw usually mature at around 6 months of age (45-50 g), but in farms it is possible to select for later maturing animals (http://www.nt.gov.au/dpifm). Since female redclaw stop growing at maturity, larger females are therefore less likely to have spawned: selecting the largest females as broodstock may affect selection for late maturing individuals.

The male reproductive system is composed of paired testes, vasa deferentia, and genital appendices; spermatogenesis occurs mainly in the seminal acini of the testes; spermatids formed after meiosis undergo a complicated metamorphosis until the aflagellate spermatozoa are formed. Mating consists in the male depositing a spermatophore on the underside of the female, from which sperm fertilizes eggs within 24 hours.

The eggs are held under the female’s abdomen until they are ready to hatch – usually 6 to 8 weeks. The larvae develop within the eggs. Embryonic development, lasting 42 days at 26°C, consists of 10 prehatching and three posthatching stages (García-Guerrero et al., 2003).

During embryonic development, eggs change colour from green to brown and orange. Finally the eggs hatch and the 12 mm long juveniles remain attached to the female for 1 to 2 days prior to moving away as completely independent miniature adults. The synchrony and degree of mating activity, the incubation period and the juvenile growth period is primarily influenced by water temperature

Under optimal pond conditions, redclaw can grow from hatching to the smallest marketable size (~30 g) within 4 months. When best practice techniques are used in farms, the majority of males will reach 100 g and females 70 g, within 12 months.

REDCLAW - EGGS