Invasive Species Compendium

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Abstract

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

Abstract

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-litre tanks, each containing 4 females and 1 male, under a constant temperature (26-28°C) and either the natural or a controlled (14 h light:10 h darkness) photoperiod. A similar annual pattern of spawning and moulting was evident under the 2 photoperiod regimes. Females spawned 3 times and moulted twice a year on average. Most spawning occurred during spring and summer, and moulting mainly occurred after the breeding season but also between spawnings. Variable sequences of spawning and moulting were evident during the breeding months in each photoperiod condition. The most common sequences were spawning-moulting-spawning and spawning-spawning-moulting, with the females as likely to spawn as to moult following the 1st spawning. An intervening spawning elongated the time between moultings but did not affect the moult increment. The number of juveniles per spawning was positively correlated with female size, whereas juvenile weight was not. There was an increase in fecundity between successive spawnings in females from the controlled, but not the natural, photoperiod, probably due to difference in their spawning history (novice and experienced spawners respectively). The environmental manipulation applied failed to maintain continuous spawning over the year in Cherax quadricarinatus broodstock.