Gå til hovedinnhold

IMR/PINRO 4/2008 Age comparison of capelin otoliths by Norwegian and Russian age readers 2004-2007 - a review


Experts from the two labs IMR in Bergen and PINRO in Murmansk met for the first time in 1984 to discuss age determination of capelin. It was concluded that no systematic differences existed between the labs (Gjøsæter, 1985). Analyses during the following years showed that during the joint autumn surveys there were, seemingly, small differences between the age readings on the different participating vessels. On the other hand, judged from catch-at-age data reported to the ICES Northern Pelagic and Blue Whiting Working Group from the winter capelin fishery in the years following the fishing moratorium 1994-1998 and from scientific surveys during the winter-spring period, large discrepancies were found, which could not be attributed to differences in length. To check the presence of systematic differences between the otolith readers at the two laboratories and to study the reasons for such differences, an otolith exchange program and biannual workshops were started. The present report gives an update of results obtained since 2003.