CRAYFISH OCCURRENCE IN RELATION TO LAND-USE PROPERTIES: IMPLEMENTATION OF A GEOGRAPHIC INFORMATION SYSTEM (GIS)

On the basis of inventory data collected since 1994, the recent stocking situation for freshwater crayfish in three 10 by 10 km study sites in northeastern Germany (Uckermark) and northwestern Poland (Szczecin area, Koszalin area) is described. The native crayfish Astacus astacus (L.) was found in two of the three study sites (Uckermark, Koszalin area) with 1 and 7 stocks, respectively, while the American species Orconectes limosus (Raf.) was found in all three study areas, and in two of them (Uckermark, Szczecin area) was the dominant crayfish species. By means of spatial analysis on the basis of a geographic information system (GIS), influence of land-use properties and other human impact on crayfish distribution was estimated. A. astacus was found only in lakes with a proportion of arable land below 10% within a 50 m buffer around the shoreline. Proportion of forest around these lakes was above the average for all lakes. In contrast, O. limosus appeared indifferent to all factors related to land use. Average lake size was clearly different for the two species. A. astacus was found in smaller lakes without direct contact to settled areas, whereas O. limosus preferentially inhabited larger lakes, indicating the importance of human activities in respect of extinction of native crayfish stocks and propagation of alien crayfish species. GIS proved a suitable tool for the assessment of land-use effects and overall human impact on crayfish distribution on a landscape level.