Abstract

Re-ageing of scales sampled in 1985 from the population of roach, Rutilus rutilus (L.), of the River Stour, England, revealed a high degree of subjectivity in their ageing, resulting from contrasting interpretations of similar scale features between practitioners. Compared with ages attained in 1985, re-ageing of the scales in 2004 only found agreement >80% at ages 1, 2, and 4 years. By age 9, agreement had dropped to 6%. The re-ageing revealed the presence of year classes that had previously been thought to have already died out and suggested their recruitment strength was associated with water temperatures in the first year of life of cohorts.