Habitat separation of the crab potamon potamios and the crayfish pontastacus leptodactylus in Lake egirdir, Turkey

Freshwater decapods rarely co-occur. The crab Potamon potamios and the narrow-clawed crayfish Pontastacus leptodactylus complex usually do not share the same pond even if they live in sympatry. An exception, however, is Lake Egirdir (Turkey), where both species are present. The aim of our study was to analyze the distribution patterns of the two species in this large lake in more detail, to better understand their ecological roles and possible interaction patterns. Our study indicated a strong segregation between the species, with crabs almost exclusively inhabiting the lake's shore area. Although the crab populations seem to have diminished recently (the reason is still unclear), they still defend this region against crayfish. More than half of the crayfish specimens and more than one quarter of the crabs had at least one melanized spot, which could be a symptom of the crayfish plague (Aphanomyces astaci). Measures are needed to guarantee the survival of indigenous crabs, which are impacted by several threats.