Abstract. In 2000 and 2001, larval vendace, Coregonus albula (L.), were marked and released into Lake Wigry. The larvae were immersed in alizarin red S. Of the 19.2 million vendace larvae released in 2000, 2 million were marked (10.4% of the overall number of fish released), and in 2001 of the 18.8 million fish released, 7 million were marked (47.8%). In subsequent years, otoliths were excised from caught vendace and the number of them with alizarin marks was determined. It was assumed that all unmarked specimens came equally from natural spawning and stocking assuming that survival is equal in both forms of recruitment. It was confirmed that 82.4% of the vendace caught from the 2000 generation originated from stocking, while this figure was 64.2% of all specimens caught from the 2001 generation. Lake Wigry hosts the most abundant vendace population in Poland, and this stock spawns on a massive scale annually. Even so, the study described herein provides evidence of just how important systematic stocking is to the maintenance of the vendace population in this lake.
Abstract. The aim of the study was to determine the age and length growth rates of vendace, Coregonus albula (L.), from Lake Wigry (northeastern Poland). Fish were captured from 2001 to 2005 in the months of August and September. The most frequent age group in the catches was 2+, which comprised 53% of all fish caught. Growth was determined using Dahl-Lee and Rosa Lee back-calculation methods. These were the basis for calculating mathematical growth rate models. The growth that best corresponded with the empirical data was that calculated with a second-degree polynomial model based on Rosa Lee back-calculations. Fish aged 3+ were characterized by average length growth and attained a mean body length (SL) of 17.2 cm.
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