Age Comparisons

Pymatuning Sanctuary Walleye

Compare age estimates from two structures taken from Walleye sampled from Pymatuning Sanctuary (PA).
Age Comparisons

Derek H. Ogle


Dec 19, 2022


Feb 13, 2023

Kocovsky and Carline (2000) examined methods to estimate the age of the unexploited population of Walleye in Pymatuning Sanctuary (PA). Scales, dorsal spines, and otoliths were extracted from fish sampled in trap nets during the spawning run in March and April of 1997. Two readers independently examined each structure without knowledge of fish length or sex. Only consensus ages for each structure are recorded in WalleyePS.1

1 See “CSV file” link in “Source” section of linked page.

  1. Describe any apparent bias (or not) between age estimates from scales and otoliths from tabular, graphical, and statistical summaries.
  2. Does the sex of the fish impact your descriptions of bias (or not) between scales and otoliths?
  3. Repeat the previous two questions for dorsal spines and otoliths.


Solution Code:

Available upon request to students not in a class. Contact fishR maintainers.


Kocovsky, P. M., and R. F. Carline. 2000. A comparison of methods for estimating ages of unexploited Walleyes. North American Journal of Fisheries Management 20:1044–1048.