Enhancement of survival and growth in crowded groups: the road towards an intensive production of the noble crayfishAstacus astacusL. in indoor recirculation systems

Abstract

High mortality from cannibalism in crowded cultures of the noble crayfish (Astacus 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 m 2 ). 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.

Growth performance of Noble Crayfish Astacus astacus in recirculating aquaculture systems

“…Energy and lipid content of feed and waterweed samples of dry matter (n = 3) Aquacult Int exhibited excellent survival and growth rates which, while lower than in the OPS treatment over the experimental period, are higher than that reported by Franke et al (2011) using comparable conditions (14-15 month-old crayfish, stocking densities of 15-60 per m 2 , LD 16:8) using a diet with higher protein levels. Specific growth rates of OPS crayfish in the current study were significantly higher than in RAS despite less optimal water conditions regarding temperature and oxygen saturation.…”

“…Other factors like water pollution and habitat alteration and destruction have led to the species now being considered endangered (Edsman et al 2010; Gherardi 2011) with only small and isolated wild populations remaining (Füreder 2009). Limited availability has increased the economic value of this once common consumer good to a luxury food product available in small quantities only on local markets for currently 35-50€/kg live weight (Taugbøl and Skurdal 1988;Franke et al 2011).…”

Lunar-Rhythmic Molting in Laboratory Populations of the Noble Crayfish Astacus astacus (Crustacea, Astacidea): An Experimental Analysis

“…Freshwater crayfish usually favor a particular time of day for molting, although there is no uniform pattern among species: nocturnal molting is known for Cherax destructor [12], while Procambarus clarkii [13] and Astacusastacus [14] molt mainly during daytime. As to a possible coupling of molting to lunar cycles, no information was available for any species of freshwater crayfish until recently.…”

“…As to a possible coupling of molting to lunar cycles, no information was available for any species of freshwater crayfish until recently. However, results reported in a recent paper [14] suggest that molting processes in a laboratory population of the noble crayfish A . astacus can be synchronized by an artificial moonlight cycle.…”

“…astacus by an artificial moonlight cycle [14] were re-examined on a larger experimental basis, and the data were analyzed with respect to possible sex-specific differences in the animals’ responses to moonlight. (2) Furthermore, an experiment was conducted to produce conclusive evidence (or counterevidence) of the moonlight cycle providing the primary source of environmental information which noble crayfish use to couple molting events to a particular phase of the lunar cycle.…”