Annual cycle of spawning and molting in the red-claw crayfish, Cherax quadricarinatus, under laboratory conditions

The annual spawning and molting cycles of the Australian red-claw crayfish was studied in the laboratory over a period of 13 months. Sexually mature crayfish were maintained in 140-1 tanks, each containing four females and one male, under a constant temperature (26–28 °C) and either an ambient or a controlled (14 L:10 D) photoperiod. A similar annual pattern of spawning and molting was evident under the two photoperiod regimes. Females spawned three times and molted twice a year on average. Most spawning occurred during spring and summer, and molting occurred mainly after the breeding season but also between spawns. Variable sequences of spawning and molting were evident during the breeding months in each photoperiod condition. The most common sequences were spawn-molt-spawn and spawn-spawn-molt, with the females as likely to spawn as to molt following the first spawning. An intervening spawning elongated the time interval between molts but did not affect the molt increment. The number of juveniles per spawn was positively correlated with female size, whereas juvenile weight was not. There was an increase in fecundity between successive spawns in females from the controlled, but not ambient, photoperiod, probably due to difference in their spawning history (novice and experienced spawners, respectively). The environmental manipulation applied here failed to maintain continuous spawning over the year in Cherax quadricarinatus broodstock.