Indirect validation of the age-reading method for Pacific cod (Gadus macrocephalus) using otoliths from marked and recaptured fish

Roberson, Nancy E. and Kimura, Daniel K. and Gunderson, Donald R. and Shimada, Allen M. (2005) Indirect validation of the age-reading method for Pacific cod (Gadus macrocephalus) using otoliths from marked and recaptured fish. Fishery Bulletin, 103(1), pp. 153-160.

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Abstract

Two examples of indirect validation are described for age-reading methods of Pacific cod (Gadus macrocephalus). Aging criteria that exclude faint translucent zones (checks) in counts of annuli and criteria that include faint zones were both tested. Otoliths from marked and recaptured fish were used to back-calculate the length of each fish at the time of its release by using measurements of the area of annuli. Estimated fish size at time of release and actual observed fish size were similar, supporting the assumption that translucent zones are laid down on an annual basis. A second method for validating reading criteria used otolith age and von Bertalanffy parameters, estimated from the tagging data, to predict how much each fish grew in length after tagging. We found that otolith aging criteria applied to otoliths from tagged and recovered Pacific cod predicted quite accurately the growth increments that we observed in these specimens. These results provide further evidence that the current aging criteria are not underestimating the age of the fish and support our current interpretation of checks (i.e., as subannual marks). We expect these indirect validations to advance age determination for Pacific cod, which in turn would enhance development of stock assessment methods based on age structure for this species in the eastern Bering Sea.

Item Type: Article
Title: Indirect validation of the age-reading method for Pacific cod (Gadus macrocephalus) using otoliths from marked and recaptured fish
Personal Creator/Author:
CreatorsEmail
Roberson, Nancy E.
Kimura, Daniel K.
Gunderson, Donald R.
Shimada, Allen M.
Refereed: Yes
Journal or Publication Title: Fishery Bulletin
Volume: 103
Number: 1
Page Range: pp. 153-160
Date: 2005
ISSN: 0090-0656
Issuing Agency: United States National Marine Fisheries Service
Subjects: Biology
Ecology
Fisheries
Item ID: 9648
Depositing User: Patti M. Marraro
Date Deposited: 14 Aug 2012 12:15
Last Modified: 14 Aug 2012 12:15
URI: http://aquaticcommons.org/id/eprint/9648

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