Occurrence of vendace, Coregonus albula [L.], and its habitats in Northeastern Poland in 1951-1994

Vendace habitats in northeastern Poland has been carried out on the basis of commercial fish catches from 1951 to 1994. The occurrence of this fish, in various time periods and in different abundance, was confirmed in 463 lakes that covered a total area of over 106.1 thousand hectares. Based on the frequency of vendace occurrence in catches, the lakes were divided into three categories. For each category, the timerelated dynamics in the number of lakes populated by vendace was described, and the relevant trend lines were plotted. Within the three categories of the habitats examined, some statistically significant differences were demonstrated between such parameters as maximum and mean depth, depth index and the percentage of the lake area occupied by pelagic waters. Vendace lived for the longest time-periods in habitats which are called vendace lakes because of their morphometric parameters. The migration of this fish species was observed. The most dynamic growth in the number of lakes where vendace was commercially exploited took place in the 1960s and 1970s. Against the background of intensive stocking operations vendace appeared, usually brief , in water bodies rather different in their morphometric parameters from vendace lakes.