Effects of eutrophication on vendace, Coregonus albula (L.). II. Biological characteristics of vendace from selected lakes in Wielkopolska

The aim of the study was to evaluate the dynamics of changes in body weight, length, and condition, as well as to determine and compare the age structure, length increments, and fecundity of vendace from four lakes in the Wielkopolska region. The smallest mean total length (21.1 cm) and body weight (82.59 g) were recorded for specimens from Lake Lubikowskie, while the greatest values were noted for those from Lake Strzeszyńskie at 23.07 cm and 118.01 g, respectively. The smallest mean value for Fulton's condition factor was noted in the vendace from Lake Lubikowskie (0.86), while the highest was noted for specimens caught in Lake Strzeszyńskie (0.93). Slightly less than 50% of the vendace caught in Lake Lubikowskie were 1-year-old-fish, whereas 2-year-old fish predominated in the other lakes. In the vendace samples from Lakes Gorzyńskie and Strzeszyńskie no 1-year-old specimens were noted, while 3-year-old fish accounted for 35.3% and 23.3%, respectively, of the total fish caught. The total length increments of vendace in the analyzed lakes were similar, and according to the classification by Szczerbowski, did not vary from the Polish mean. The highest absolute fecundity was observed in fish from Lake Gorzyńskie, but it was considerably lower (almost two-fold) in the vendace caught in Lake Strzeszyńskie.