Workshop on Megrim Otolith Age Readings

Since 1997, there has not been an exchange and workshop on Megrim Ageing. The last one was carried out under the auspicious of EC Study Project Contract No. 95/038 “Biological Studies of Demersal Fish (BIOSDEF)” deployed from 1996 to 1998. To address possible problems that could have raised, an otolith exchange was recommended between readers involved in the assessment and a posterior workshop was carried out. The results of the Megrim otolith exchange conducted in 2004 indicate that the age estimation criteria adopted seem to be appropriate (see Annex 3). A second reading of a subset of the exchange otolith collection (n: 39 otoliths with their corresponding images) was undertaken during this workshop. In general the results indicate that the percentage of agreement increased. The results of this workshop indicate that the precision of age readings (CV) decreased, probably due to the smaller sample size of the collection although the average percent of error also decreases. Thus, the values of APE and CV in (%) for all readers were 16 and 21.5, and 18 and 12.6 % respectively for the real and image otolith collection. The analysis of these results shows that there are no serious deviations in the otolith readings. The comparison of these results with those from the previous workshop conducted in 1997 shows that the criteria is firmly established due to the consistency of the results.