External morphology and growth rate of white-eye bream Ballerus sapa (Cyprinidae, Teleostei) in a lowland dam reservoir on the lower Vistula River (Wloclawek Reservoir, central Poland)
2008
Kakareko, T.,Nicolaus Copernicus Univ., Torun (Poland). Dept. of Hydrobiology | Kobak, J.,Nicolaus Copernicus Univ., Torun (Poland). Dept. of Invertebrate Zoology | Terlecki, J.,University of Warmia and Mazury, Olsztyn (Poland). Dept. of Applied Ecology | Hadowski, M.,Nicolaus Copernicus Univ., Torun (Poland). Dept. of Hydrobiology
The aim of this study was to compare the morphology and growth rate of Ballerus sapa specimens inhabiting a dam reservoir on the lower Vistula River (Poland) with those from other waters of native and non-native regions of this species. Altogether, 24 mensural and 15 qualitative characters of 93 individuals and age of 108 specimens were determined. There were significant differences in morphometric characters among the studied population and those from the Zegrze Reservoir (Vistula River catchment) and the Dnieper River. Meristic characters showed considerable overlap with the literature data except the number of unbranched fin rays which revealed greater variability. The growth rate of the white-bream from the Wloclawek reservoir was moderate in the first year of life, and then it was faster than in many waters from its native range. This marked increase of growth rate seemed to be site-specific rather than region-specific and associated with particularly rich feeding resources (abundant bottom fauna) of the eutrophic and strongly flowing dam reservoir.
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