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Developing Ageing Criteria for Shortraker Rockfish

Alaska researchers in the Age and Growth Program thin sectioning otolith techniques.

A shortraker rockfish otolith

A shortraker rockfish otolith thin section photographed in the AFSC Age and Growth Laboratory with transmitted light at a magnification of approximately 28X and aged to 104 years. Photo by Karna McKinney and Charles Hutchinson.

Beginning in 2000, the Alaska Fisheries Science Center Age and Growth Program began investigating new methodologies for ageing shortraker rockfish. The methodology known as thin sectioning proved better than the break and burn method at eliminating burning artifacts and glassy areas in the reading surface of the otolith. Using the thin section method, three different strategies were examined based on growth patterns seen on the otoliths, including determination of a "transition age," an age where the fish’s somatic growth slows. Ages using the different strategies were compared to radiometric ages to determine which strategy was most accurate. The use of radiometrics was also used to validate the transition age in shortraker rockfish.

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