Report of the Workshop on Age Reading of Sea Bass (Dicentrarchus labrax) (WKARDL)

The Workshop on Age reading of Sea bass (Dicentrarchus labrax) (WKARDL) was heldin Lowestoft, England, UK, from the 15th to 19th June 2015. The meeting was chairedby Kélig Mahé (France) and Mary Brown (England UK), and included seven agereaders from three countries. The objectives of this first workshop were to review,document and make recommendations on current methods of ageing sea bass. This workshop was preceded by otolith exchanges in 2011 and 2013, which were undertakenusing WebGR. Participants, who had not taken part in the exchange were askedto annotate the images in the months prior to the workshop. However, due to problemswith accessing WebGR only a limited number of the readers managed to do thisin time.Seven readers participated in a scale calibration exercise during this workshop whichshowed an overall agreement of 78.2% (ranging between 29 and 100%) with a precisionof 5.2% CV (ranging from 0 to 13%). Of the 55 scales, 24 (43%) were read with100% agreement. The image analysis exercise clarified that the lack of agreement canbe due to the difficulty identifying the position of the first annulus, the presence ofchecks and the dates of sample collection.

The workshop achieved quite a lot in terms of ironing out, through discussion and calibration, some of the major difficulties in ageing otoliths of sea bass. This group recommend use of scales for sea bass ageing. For future exchanges, it would be bene-ficial to compare unstained otolith sections with transmitted and reflected lights and stained otolith sections, with the scales. For scale exchanges, the group recommend the use of multiple scale images (or videos) for each fish. The group reached agree-ment on a definition of an ageing guideline and a reference collection presented in this report and the aim is to employ these tools for all laboratories.