On the accuracy of age‐determination using scales from rudd, Scardinius erythrophthalmus (L.), of known age

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Abstract
Six scientists from five European countries each examined 29 sets of scales from rudd of known age. The material contained 174 scales from both fast and slow growing fish and, with the exception of one participant, the scientists missed the first annulus when it was formed close to the scale centre. Sixty‐eight scales were misread in this way, but only 12 were incorrectly aged because of confusion between true and false annuli. Comparisons of back‐calculated lengths with observed lengths at each age were used to identify which false annuli had been incorrectly identified as true annuli, and vice‐versa. The results confirmed the necessity of having information from other sources, e.g. seasonal length‐frequency distributions of 0‐group fish, to support the subjective interpretation of the scales.