Daniel A. Isermann
Ryan P. Koenigs
Daniel J. Dembkowski
2019
<div class="abstract-group"><div class="article-section__content en main"><p>Within most resource management agencies, fish ages assigned by multiple readers are used to estimate age-based population metrics and to develop state or regional growth standards under the assumption that among-reader precision and accuracy are high. A cursory evaluation suggested that precision of age estimates among seven individuals who routinely estimate Walleye<span> </span><i>Sander vitreus</i><span> </span>age for the Wisconsin Department of Natural Resources was remarkably low (otolith mean coefficient of variation [CV] = 37%; dorsal spine mean CV = 35%), which prompted concern and interest in whether among-reader precision could be improved with a minimal level of training. Consequently, we compared among-reader precision and accuracy before and after a 1-d training exercise. We distributed images of sectioned otoliths and sectioned dorsal spines from a random sample of 50 Walleye, along with images of structures from 25 known-age Walleye, to 21 readers grouped into beginner, intermediate, and advanced experience levels based on responses to a pretraining survey. Among-reader precision was substantially higher after training (otolith mean CV = 16%; dorsal spine mean CV = 15%) than before (otolith mean CV = 27%; dorsal spine mean CV = 26%). Accuracy of age estimates also improved after training, but greater improvements were observed for otoliths (mean difference between estimated and known ages before training = 0.80 year; after training = 0.15 year) than for dorsal spines (mean difference between estimated and known ages before training = 0.38 year; after training = 0.22 year). Similar improvements in precision and accuracy were evident for all experience levels. Our results suggest that a simple, low-cost age estimation training can substantially increase precision and accuracy of age estimates among a large group of readers. However, additional training and quality control measures may be required to achieve higher levels of precision and accuracy.</p></div></div>
application/pdf
10.1002/nafm.10293
en
American Fisheries Society
Potential for improving among-reader precision and accuracy of Walleye age estimates with minimal training
article