There is growing interest in using recirculating aquaculture systems (RAS) to raise noble crayfish Astacus astacus a valuable and once plentiful food species in Europe, now a highly endangered species. The growth and survival of A. astacus was compared in growth trials in RAS and open-pond systems (OPS) over a period of 2 months. Energy and lipid content of available diets and crayfish tissue were also determined. Growth of A. astacus during summer was significantly (p \ 0.01, one sample t test) higher in OPS (SGR 1.23) than in RAS even at the highest feeding ration provided at 5 % bw/d -1 (RAS HI SGR 0.78 ± 0.06). OPS crayfish also had significantly (p \ 0.01 OPS vs. all RAS treatments; Pairwise Wilcoxon) higher lipid content (8.51 %) than RAS crayfish (RAS HI 5.73 %, RAS MED 6.93 %, RAS LOW 5.92 %). Survival rates in RAS were, however, 100 % compared with previous observations in OPS of approx. 70 %. While results showed OPS growth exceeds than that in RAS in the short term, RAS survival rates and annualized growth performance may outweigh this disadvantage, particularly if optimal artificial diets for RAS holding are provided. Feed and crayfish analysis indicated that culturing A. astacus in RAS require a diet protein content exceeding 30 % and lipid content of \13 %, indicating that the carp diet supplied was not optimal. RAS culture allows this valuable species to be cultured in controlled, disease-free enclosed systems-resulting in high-value food products as well as high-quality seedlings for restocking purpose.

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There is growing interest in using recirculating aquaculture systems (RAS) to produce juvenile noble crayfish, Astacus astacus (Linnaeus), a valuable and once plentiful food species in Europe, now a highly endangered species. The survival rates of early stripped eggs of A. astacus were compared across anti-fungal treatments in an artificial RAS incubation system based on a saline bath of approx. 20 -22 mS cm -1 or 15 -16 PSU over two different durations. Time from fertilisation to hatching was 82 days or 1191 degreedays. Low survival rates (live successfully hatched juveniles at end of experimental period) between 11.0 ± 9.5% and 26.6 ± 3.7% were obtained. Survival was significantly affected by the duration of egg bath within the saline solution with twice as high survival rates when eggs were saline-bathed once every two days for five minutes in comparison to eggs without treatment. Fungal rates were significantly affected by treating the eggs with a saline solution with infection rates decreasing from 3.7 ± 1.0% to 0.8 ± 0.5% in the ten minute saline bath treatment. Appropriately applied saline bathing can markedly improve survival of early-stripped noble crayfish eggs. However, further research is required to determine whether viable levels of hatching success can be obtained using early stripping and saline treatment.