Age and growth rate of asp (Aspius aspius) from the Pierzchały Reservoir were estimated by back calculations based on scale readings (annual rings identification). The scale reading procedure was complicated by presence of additional rings, called "juvenile" (these appearing within the first year′s increment) and "spawning" (present on scales taken from individuals older than 3 years). These additional structures were not characteristic for all the examined individuals. Localisation of the first annual ring was complicated by fairly fast growth rate during winter, so the typical zones of narrow sclerites, indicating slow-growth season did not occur, affecting the scale readability. The quantitative share of asp in control catches amounted to 9%. Most of these individuals (70%) were to 4 to 7 years old. The oldest asps were aged 12, at body length of 66 cm and body weight of 4500 g. The Pierzchały Reservoir is merely exploited by fishermen.
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