Otolith Annulus Interpretation Dave Buckmeier, Texas Parks and Wildlife SDAFS Catfish Technical Committee 2005 Catfish Age Workshop

Considerations Time of annulus formation YC versus age assignment Time of collection Limit data provided to reader Sources of error Quality control: methods to improve accuracy

Annulus Formation – Alabama CC

YC versus Age Assignment Age assignment typically uses an arbitrary birthday making it difficult to standardize N Collected January 2005 Jan B-day=3, Jun B-day= YC (2.6 years old)

Time of Collection Fish collected in the same year with equal number of annuli may not be the same age May YC (6.9 years old) September YC (6.3 years old)

Data Provided to Reader Date: Lake: Weiss Site: 4 Species: Channel Catfish TL (mm): 452 Weight (g): 1814 Reference #: W-154 Date: Species: Channel Catfish Reference #: W-154

Sources of Age Estimation Error Structural Processing Interpretation

Sources of Age Estimation Error “A validated ageing method confirms the frequency of formation of growth increments in a given structure, and confirms that they have been interpreted correctly by the age readers in the study. However, there is no guarantee that the same interpretation would be reached by other age readers, even when viewing the same structures.” S. E. Campana (2001)

Methods to Improve Accuracy Training and practice Consensus age estimates Testing

Annulus Interpretation Collected Nov. ’04 Collected July ’04

Annulus Interpretation Collected Nov. ’ YC Collected July ’ YC

Original presentation had embedded videos here. These are posted separately on the Catfish Management Technical Committee website to keep the file size of this powerpoint small.