Morphometrics, fecundity, density, and feeding intensity of the spinycheek crayfish, Orconectes limosus (Raf.) in natural conditions

Three populations of spinycheek crayfish, Orconectes limosus (Raf.) from Polish lakes (Staw Plociczno, Dgal Wielki, Hancza) were studied. The aspects of the spinycheek crayfish studied were the morphometric characters of females and males, individual absolute fecundity, sex ratio, size structure, density, biomass, and feeding intensity in an annual cycle. It was determined that the body proportions of males in forms I and II differed significantly, while the body proportions of female spinycheek crayfish were similar to those of form II males but different from the body proportions of form I males. The crayfish investigated in the current study had a lower individual absolute fecundity than did spinycheek crayfish of the same body weights from other Polish basins. The crayfish predicted daily food ration (RdP) exhibited a very strong relationship with the stomach fullness index (If) and water temperature (t). The empirical formula of this relationship (ln Rd P = 0.397 + 0.094 t + 0.614 ln If) permitted estimating the daily food ration. The crayfish fed most intensely from the May to October period, during which they consumed in excess of 80% of their annual ration. The primary dietary component of the spinycheek crayfish was plant matter. Annually, the crayfish population consumed barely 0.27% of the wet weight of the aquatic vegetation in its range of occurrence.