Distribution, population structure and conservation of Austropotamobius pallipes in Portugal

Abstract

Austropotamobius pallipes has suffered a considerable reduction in range and abundance over the last two decades. The main hypotheses to explain this situation are : environmental degradation, critical climatic conditions, and the crayfish plague, though the presence of Aphanomyces astaci as the aetiological agent is to be confirmec. White-clawed crayfish populations are now confined to a few small areas in the north-eastern part of the country and risk total extinction. Population characteristics are presented. Sex ratio is balanced and maximum size is small, very few individuals being larger than 75 mm. Four age-classes were identified through modal analysis. Females become sexually mature during the second year. Several conservation actions are proposed.