Ultraviolet light and semi-recirculating systems in artificial incubation of noble crayfish (Astacus astacus) eggs: opportunities and limitations

Development of artificial crayfish egg incubation is a milestone in intensive culture of crayfish as commercially important freshwater animals. This study evaluated experimental treatments combining continuous UV lighting, a non-chemical antifungal treatment, with an initial formaldehyde bath for noble crayfish (Astacus astacus) eggs incubated in semi-recirculating systems, which requires less than 1 per cent the amount of water necessary for conventional flow-through systems. The one-time administration of a pre-incubation bath to reduce formaldehyde exposure was ineffective. Ultraviolet irradiation of recirculating water provided poor results (13.5% and 35.2% final survival rates to stage 2 juveniles) and led to deteriorating water quality. An inability of hatchlings to successfully moult and the occurrence of limb deformities was observed in UV-treated groups, and juvenile mortality was found across all experimental treatments.