freshwater drum, otolith, aging methods, Mississippi River
A comparative aging study was conducted using scales and otoliths from 123 freshwater drum collected in Pool 14 of the Mississippi River. Two independent readings by 2 investigators resulted in full agreement on ages assigned using otoliths, but only 64% agreement using the scale method. A final age was determined for the remaining scale samples based on the most commonly assigned age. However, there was no agreement on assigned ages for 12% of the scales examined. Otoliths were validated as an accurate method for aging freshwater drum by age frequency histograms for 3 consecutive years. The marked 3-year periodicity in appearance of strong year-classes allowed these strong year-classes to be followed through successive years of study providing a check on the reliability of this aging method. Scales were concluded to be only 61% reliable for aging freshwater drum. The observed trend indicated that assigned ages using scales were commonly overestimated for fish age 9 and younger and underestimated for older fish.
Proceedings of the Iowa Academy of Science
© Copyright 1984 by the Iowa Academy of Science, Inc.
Goeman, Timothy J.; Helms, Don R.; and Heidinger, Roy C.
"Comparison of Otolith and Scale Age Determinations for Freshwater Drum from the Mississippi River,"
Proceedings of the Iowa Academy of Science: Vol. 91:
, Article 3.
Available at: http://scholarworks.uni.edu/pias/vol91/iss2/3