"on the Screen or Though the Scope: Does Viewing Method Influence Age Estimates for Largemouth Bass and Walleyes?"

Abstract.— Many biologists now use digital images in the process of estimating the age of fish. However, capturing an image of a calcified structure can result in changes in light and clarity when compared to directly viewing structures using a microscope. These differences could result in differences in age estimates obtained from the same structure. Our objectives were to determine if: 1) otolith-based age estimates for largemouth bass Micropterus salmoides and otolith- and dorsal spine age estimates for walleyes Sander vitreus were similar when annuli were enumerated directly through a microscope or from digital images viewed on a computer monitor and 2) if trends in age assignments between the two viewing methods were similar among readers with varying levels of experience. Using samples of largemouth bass and walleyes collected from multiple Wisconsin lakes, we determined that ages estimated using the two different viewing methods were…and this was consistent among readers with varying levels of experience in assigning ages.