Results of reading tests of TOP otolith sections and time schedule of reading for Dissostichus otoliths caught in regions of data-poor fisheries

The correct age-length keys are essential for the stock assessment of Dissostichus spp. by CASAL model. However, the age estimations using the otoliths have been scarcely progressed in regions of data-poor fisheries. Therefore the analysis is an urgent task. We have made five reading tests using images of thin-sectioned TOP otoliths in December 2012 and May 2013. The coefficient of variation between “known ages” by AAD (Australian Antarctic Division) and those estimated by the first author (Taki) is lower than the threshold of 10 % for five tests, with one of them being close to 10 %. This suggests that his reading clear the standard by NIWA (National Institute of Water and Atmospheric Research Ltd, in New Zealand). He will continue to make the periodical reading test for TOP otolith sections. On the other hand, a total of 60 TOA otolith references by bake-and-embed method were provided by CCAMLR Secretariat in this February. We will make image processing for these references and also conduct the periodical reading tests using the images. In addition, we plan to train the second reader referring to the standard protocols by NIWA and AAD. We aim to establish the reading technical skill for TOA otolith sections by next year (2014). The size-age data will be applied to CASAL catch-at-length and catch-at-age models in 2015 and later.