Age, growth rate, and condition of vendace, Coregonus albula (L.), from some Pomeranian Lakes (NW Poland)

Background. Vendace, Coregonus albula (L.), is one of the most valuable components of Polish lake ichthyofauna. The vendace from different lakes differ in their principal vital characteristics (such as growth rate etc.) and it is therefore crucial to determine those characteristics from different throphic types of lakes in order to implement proper measures of fisheries management for those coregonids. The aim of the present paper was therefore to learn principal biological features of vendace populations representing three different Pomeranian lakes. Materials and methods. Comparative biological studies were carried out on 136 vendace from Pełcz Wielki Lake, 304 from Bytyń Wielki Lake, and 62 from Wełtyń Lake (Pomerania Lakeland) collected within 2002-2003. The age and growth rate of the fish were determined from scales. Fulton′s condition factor and the total length-weight relation were used to determine fish condition. Results. Gillnet selectivity influenced fish age structure and size. For example, among 502 vendace obtained, in total, from the three lakes, 75.7% (380 specimens) were 2+. The results of back-calculations and the parameters of von Bertalanffy′s growth equation revealed distinct disproportions in the total length in individual age groups (Pełcz Wielki Lake: Lt = 213.22[1 - e-0.49576(1 + 1.055013)]; Bytyń Wielki Lake: Lt = 219.17[1 - e-0.733553(1 + 0.040147)]; Wełtyń Lake: Lt = 255.08[1 - e-0.571108(1 + 0.023036)]) Slower length- and weight growth rates were observed in the fish from Pełcz Wielki Lake. Conclusion. The growth rates, determined using back-calculations, were different for the vendace populations representing lakes Pełcz Wielki, Bytyń Wielki, and Wełtyń in the sequential years of fish lives. The fish from Wełtyń Lake were characterized by average growth, whilst the fish from the remaining reservoirs were characterized by slow or very slow growth. The lower condition values and growth rates from Pełcz Wielki Lake were probably the result of poor environmental conditions in this body of water.