Report of the Workshop on Age Reading of horse mackerel (Trachurus trachurus), Mediterranean horse mackerel (Trachurus mediterraneus) and blue jack mackerel (Trachurus picturatus) (WKARHOM)

A Workshop on Age Reading of horse mackerel (Trachurus trachurus), Mediterranean horse mackerel (Trachurus mediterraneus) and blue jack mackerel (Trachurus picturatus) (WKARHOM), chaired by Alberto Murta (Portugal) and Pablo Ablaunza (Spain), will exchange information by correspondence in 2011 and meet in Lisbon (Portugal), 2327 April 2012, to:

1 ) Review information on age determination, and validation on these species;

2 ) Compare different otolith-based age determination methods;

3 ) Identify sources of age determination error in terms of bias and precision: i.e. analyse different validation techniques and describe the corresponding interpretational differences between readers and laboratories, and agree on a common ageing criteria;

4 ) Analyse growth increment patterns and provide specific guidelines for the interpretation of growth structures in otoliths;

5 ) Create a reference collection of otoliths and start the development of a data-base of otolith images.

And to address the generic ToRs adopted for workshops on age calibration, which are:

6 ) Provide information on participating laboratory procedures: Sampling and storing of calcified structures;  equipment and preparation of calcified structures; documentation on processes and protocols (QA); how age determination are being checked within laboratories (QC): availability of reference collections, results of age reading comparisons between readers, percentage of samples re-read; and estimate (relative) accuracy and precision;

7 ) Resolve interpretation differences between readers and laboratories;

8 ) Create or update an ageing manual;

9 ) Collate agreed age reference collection;

10 ) Formulate follow-up actions;

11 ) Formulate species (and stock specific) target and threshold statistics.