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Wednesday, January 27 • 10:20am - 10:40am
Precision of Estimating Ages of Yellow Perch Using Dorsal and Anal Spines

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AUTHORS: William D. Oeming*, LTBB NRD; Jason B. Smith, LTBB NRD; Kevin C. Donner, LTBB NRD

ABSTRACT: Yellow perch Perca flavescens are an important species to subsistence and recreational fishermen in Lake Michigan. Age data collected for yellow perch in Lake Michigan are assessed annually by numerous fisheries management agencies lakewide. These agencies use different physical structures to estimate ages of yellow perch including dorsal spines, anal spines, otoliths and scales. Our objective was to determine whether dorsal or anal spines were more precise for estimating age. We evaluated estimated ages within and across readers as well as perceived ease of reading for each spine. To do this, we collected 30 yellow perch from Lake Michigan. We then extracted, prepped and mounted all dorsal and anal spines from each fish in a hardened epoxy. Each spine was sectioned into three, 2 mm-thick pieces using an IsoMet Low Speed Saw. Each section was then photographed, cataloged, randomized and aged independently by three different readers. In addition, each photograph was assigned a score (1 to 5) based on its ease of reading. Estimated ages ranged from two to eight years old. Across readers, the range of agreement for anal spines was higher (from 72% to 82%) than for dorsal spines (from 54% to 72%). The largest age discrepancy across readers for anal spines was only 2 years while for dorsal spines it was 5 years. Within reader agreement was also somewhat higher for anal spines (from 63% to 73%) than for dorsal spines (from 59% to 68%). Similarly, within reader agreement for anal spines had a lower age discrepancy (up to 2 years) than dorsal spines (up to 4 years). Also, readers judged anal spines (1.7) to be easier to read than dorsal spines (2.7). It is our conclusion that anal spines are more precise than dorsal spines for estimating ages of yellow perch. 

Wednesday January 27, 2016 10:20am - 10:40am EST
Gerald Ford