Population structure and dynamics and habitat conditions of the native crayfish Austropotamobius pallipes in a pond : a case study in Basque Country (Northern Iberian Peninsula)

A natural and in appearance healthy population of the native crayfish Austropotamobius pallipes inhabiting a pond near Bilbao has been studied for three years, together with abiotic conditions of their habitat. The population occupies a littoral fringe (100 m length, 6 m width and approximately 1.5 m maximum depth), and has an estimated average density of 1.67 specimen/m2. Despite the very high conductivity of the water (all values are above 1,750 µS/cm), total net production in the period 94-96 was 2,571 . ± 460.0 g (4.3 ± 0.8 g/m2), with a productivity rate of 0.18 ± 0.04 measured as Production/Biomass (P/B) index. We think that population equilibrium with the carrying capacity of the pond ecosystem is reached