Precision of Scales and Dorsal Spines for Estimating Age of Common Carp

We examined precision in age estimates from common carp (Cyprinus carpio) scales and dorsal spines sampled from 28 Iowa lakes (N = 501 individual fish). Exact agreement between two readers was 28.5% for scales and 90.6% for dorsal spines. Agreement of scale ages between readers was poor across the distribution of assigned ages. Agreement of dorsal spine ages increased to 95.8% after a joint examination conducted to assess reasons for disagreements. Age estimates from scales were as much as eight years less and seven years greater than ages estimated from dorsal spines, and discrepancies occurred in young as well as old fish.