Age and growth rate of vendace (Coregonus albula (L.)) from Lakes Siecino and Miedwie in Poland
Lampart-Kałużniacka, Magdalena; Heese, Tomasz
Age is one of the basic elements applied in the estimation of the mortality rate, growth rate, production and other biological features of fish. It is usually most easily determined by analysing scales, but otoliths or fin spines are being used more and more frequently as more reliable structures. Due to this, these structures were used in order to estimate the ages and growth rate of vendace from two lakes of the Pomorze Region of northern Poland, i. e. Lakes Siecino and Miedwie. According to this study, the most numerous fish were of age 3+ and 4+ for Lake Siecino, and age 5+ for Lake Miedwie. The smallest fish with a total body length of 155 mm were also the youngest and aged 1+ for both lakes. The largest specimen was recorded in Lake Siecino, with a total body length of 288 mm and an estimated age of 4+. The oldest fish from Lake Miedwie were smaller, with L. t. varying from 220 to 235 mm and an estimated age of 6+. Fish from Lake Miedwie had a faster growth rate. However, body lengths determined by back-calculation for vendace from Lake Miedwie were low. This suggests that the estimated ages for this lake were inflated and that the fish in fact had a maximum age of 4+. Reasons for the appearance of additional annual marks can be numerous. In this case, it is probably related to the proceeding eutrophication of the lake and changes in the thermal stratification of its waters.