Report of 4th Exchange on European hake age readings

Abstract

In 2002 the ICES WGSSDS showed the difficulties in the assessment of hake due to uncertainty on age estimation of older fish which has led the WG to use a plus group at age 8. To solve these problems an otolith exchange was recommended between readers involved in the assessment and focused mainly on older fishes. Preliminary results of the fourth hake otoliths exchange, conducted in 2003, indicate that the age estimation criteria used up to age 3 was the one adopted previously, however, for older fishes, otolith interpretation presents a higher complexity. The results indicate that the precision of age readings has decreased and a strong bias has been found in age readings of older fishes. Thus, the values of APE and CV in (%) for all readers are 41, and 45 respectively, while the values for assessment readers are 24 and 32. The comparison of these results with those from the previous exchange in 2001 shows the difficulty of this task, and to solve these problems a specific international workshop will be carried out.