Hake age estimation: state of the art and progress towards a solution
Since 1992, northern and southern hake (Merluccius merluccius) stock assessments have used age data based on otolith analysis. Age data for stock assessment is provided by different institutions, which implies a quantification of age‐reading precision to estimate assessment quality indicators. During this period, considerable effort has been made to improve the precision of age data by means of successive age reading calibration exercises, exchanges, and workshops in 1997, 1999, 2001, and 2004. This goal was partly achieved, and experts recently agreed on standard criteria (Piñeiro and Saínza, 2003) that allowed an acceptable precision to be reached for ages up to 3 years (Piñeiro et al., 2004). However, these criteria have never been validated, and recent mark ‒ recapture experiments are not in line with ageing results based on the standard criteria. Given the impact of bias in age estimation on stock assessment results, consequent management advice, and concern about the state of the hake stocks (ICES, 2007a, 2007b), a report on the current state of the art is needed. The main goal of this report is to present a synthesis of the work carried out over the years by researchers involved in providing age data for stock assessment, mainly on age‐reading calibration exercises, and current knowledge regarding the growth and ageing of this species. This report also includes recommendations for future work aimed at achieving validated age‐reading criteria.