Enhancement of survival and growth in crowded groups: the road towards an intensive production of the noble crayfish A stacus astacus L. in indoor recirculation systems.

High mortality from cannibalism in crowded cultures of the noble crayfish ( A stacus astacus L.) was the reason why the efforts for an intensive production of this species in the 1980s were largely stopped. In the present study, 14- to 15-month-old juveniles of A . astacus were cultured in tanks of an indoor recirculation system under constant 'summer conditions' (19°C, LD 16:8) from early August to late January. The animals continued to moult and grow, indicating that the absence of these processes in the field from autumn to late spring does not involve any endogenous programming. The experimental design (suitable hiding places in excess, highly diversified diet, and special daily and lunar light regimes) ensured high survival (>90%) and growth rates which were largely independent of stocking rate (15-60 individuals per m2). Moulting occurred during daytime which allowed freshly moulted animals to escape from cannibalistic attacks of their nocturnal conspecifics. There is a first indication that an artificial moonlight cycle can synchronize moulting events (maximum around 'new moon'), in this way contributing to a further decrease in mortality. The results encourage a resumption of efforts for an intensive production of A . astacus in indoor recirculation systems. [ABSTRACT FROM AUTHOR]