Abstract
The aim of this study was to determine the impact of filamentous algae on the growth and survival of juvenile narrow-clawed crayfish, Astacus leptodactylus (Esch.), in rearing basins. Three stocking variants were used: A - basins with a layer of filamentous algae without imitation mineral substrate; B - basins with a layer of filamentous algae with imitation mineral substrate; C - basins without filamentous algae but with mineral substrate. The crayfish were reared from June 12 to October 10 under natural thermal conditions and fed a commercial feed. The results indicated that the presence of the filamentous algae did not have a statistically significant impact on the growth of the juvenile crayfish (P > 0.05). The presence of the filamentous algae had a strong negative impact on juvenile crayfish survival and stock biomass (P < 0.05). The layer of gravel and small stones that imitated the mineral substrate of natural aquatic basins somewhat neutralized the disadvantageous impact the filamentous algae had on the crayfish.