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NAFO SC Studies No. 41 (2008)

Report of the Greenland Halibut (Reinhardtius hippoglossoides) Age Determination Workshop

Report of the Greenland Halibut (Reinhardtius hippoglossoides) Age Determination Workshop

(pdf 5.5 mb)

M. A. Treble and K. S. Dwyer

Abstract

The workshop was held in St. John’s, Newfoundland and Labrador, February 21–24, 2006. Prior to the workshop there was an exchange of otoliths and scales collected during the 2005 EU survey in SA3. During the workshop each lab presented information on ageing methods using scales, otolith whole and otolith section: no two labs used the same method. Research related to methods and age validation was also presented. Observations have been made in recent years that suggest Greenland halibut are longer lived and slower growing than previously thought. The otolith cross-section methods presented during the workshop indicated older ages at a given length compared to surface ages. For the Alaskan stock it was suggested the methods deviate beginning at approx. 60 cm or age 7 yr. For the stock in NAFO SA0 deviations in the age bias plot of whole versus section age estimates began at about age 15 (approx. 50 cm). For the Northeast Atlantic stock off the Norwegian coast ages derived from a revised whole otolith method began to deviate beginning at ages 4–5 (approx. 40 cm). Dark “featureless” translucent margins on large otoliths indicate an accumulation of compacted small annual zones. It became clear during the workshop that bias between age readers could not be solved by simply agreeing to common interpretation practices. Workshop participants provided several conclusions and recommendations.

 

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