Accuracy and Precision of Age Estimation of Crappies

Abstract

A collection of known-age black crappies Pomoxis nigromaculatus and white crappies P. annularis (ages 1–5) was used to evaluate the accuracy and precision of ages estimated from otoliths and scales by readers of varying experience levels. Age estimation accuracy for black crappie otoliths averaged 99.6%, whereas accuracy for scales was 77.6%. Accuracy of age estimates from white crappie otoliths averaged 98.5%, whereas accuracy of estimates from scales averaged 80.4%. For both species, age estimation precision was higher for otoliths than for scales. Reader bias (e.g., difference between true age and estimated age) tended to be greater for scales than otoliths in both species. Bias in otolith age estimation was minimal and only apparent for age-5 crappies, which were consistently underaged. Bias in scale age estimation was most apparent for age-4 and age-5 crappies, which were also typically underaged. Reader experience influenced the degree of precision and bias; experienced readers produced more precise and less biased age estimates. The use of otoliths to improve crappie age estimate precision and bias has been well documented. Through the use of known-age fish, we provide evidence that age estimate accuracy can also be improved.