Otolith Annulus Interpretation

Dave Buckmeier, Texas Parks and WildlifeSDAFS 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

Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug

(Mar

gina

l Inc

rem

ent /

Oto

lith

Rad

ius)

x 1

00

0

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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=2• 2002 YC (2.6 years old)

Time of CollectionFish collected in the same year with equal number of annuli may not be

the same age

May 20102003 YC (6.9 years old)

September 20102004 YC (6.3 years old)

Data Provided to Reader

Date: 2-11-05Lake: WeissSite: 4Species: Channel CatfishTL (mm): 452Weight (g): 1814Reference #: W-154

Date: 2-11-05Species: Channel

CatfishReference #: W-154

Sources of Age Estimation Error

StructuralProcessing

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. ’042001 YC

Collected July ’042002 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.