otolith annulus interpretation
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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
10
20
30
40
50
60
70
80
90
100
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.