Muskellunge Scale Interpretation: The Question of Aging Accuracy

Abstract

Abstract Age and growth data extracted from scales are often used when managing fish populations. However, accurate interpretation of scale annuli in certain species, such as muskellunge Esox masquinongy, has been suspect. The accuracy of age determination was tested with three experienced esocid scale readers who interpreted positive photo images made from acetate slide impressions projected on a microfiche reader. Images were made from scales of 25 known-age muskellunge (3–10 years old) from five Wisconsin lakes. Each scale image was interpreted twice; once with fish length, sex, and date of capture given and once without any information. Of 149 scale interpretations, 32% were assessed with the correct age, 54% underaged, and 14% overaged. The average interpretation deviated from the known age by 1.0 years. Accuracy did not improve when additional fish information was available. General confidence in the interpreter's age assessments was low and possibly related to quality of the photo images. Interpret...