Workshop on micro increment daily growth in European Anchovy and Sardine (WKMIAS). 21-25 October 2013 Mazara del Vallo, Sicily
|Ref.||ICES CM 2013/ACOM:51|
|Note||ICES WKMIAS REPORT 2013 ICES ACOM COMMITTEE REF. PGMED AND PGCCDBS|
|Abstract||The Workshop on Micro increment daily growth in European Anchovy and Sardine (WKMIAS) met for the first time from 21-25th October 2013 in Mazara del Vallo, Sicily (CNR-IAMC). The meeting was chaired by Gualtiero Basilone (CNR-IAMC, Italy), Begoña Villamor (IEO, Spain) and Mario La Mesa (CNR-ISMAR, Italy). Six nations were represented by 22 participants.
WKMIAS was proposed by the Planning Group on Commercial Catches, Discards and Biological Sampling (PGCCDBS) 2012. Many activities of this group are closely linked to the activities of the Data Collection framework (DCF). Although under the ICES have been made multiple age reading workshops at annual scale, this was the first time that a workshop was dedicated exclusively to age reading at daily scale. The objectives of the workshop were to define and standardize methods, reading criteria and proto-cols of anchovy and sardine daily growth in different developmental stages (larvae and juveniles), and validate the first annual ring of these species to improve annual age estimates. The report summarizes the work in relation to each of the ToRs.
Given the terms of reference and objectives, the daily growth of these species is dealt with the following geographical areas/stocks/ecosystems: Bay of Biscay, Atlantic Ibe-rian Peninsula (sardine only), Western Mediterranean, Strait of Sicily, Adriatic Sea and North Aegean Sea.
Before the workshop, a questionnaire was performed in which each laboratory should provide information on their method of preparation and interpretation of the anchovy and sardine otolith microstructure. The result of them was reviewed and summarized, reaching a common protocol during the workshop regarding the methods and tech-niques of preparation of the otoliths. However, there was not agreement in relation to daily increment interpretation criteria.
The workshop also was preceded by an otolith image exchange, which was undertaken using EARF in the months prior to the workshop. The exchanged otolith collection in-cluded 81 images (41 for anchovy and 40 for sardine) distributed in 10 sets from differ-ent anchovy and sardine distribution areas. In the case of sardine, also a small otoliths collection (5) of known age (obtained from Aquaculture) was used. The exchange proved the existence of differences between readers and areas of both species, with a precision ranging from 9.0 to 34.9% CV for anchovy, and from 9.4 to 18.0% CV for sar-dine. The comparison with the actual age of sardine (known from marine culture) showed that sardine readers are generally in good agreement; nevertheless all readers underestimated the older fish.
During the workshop a reading exercise on live images of anchovy and sardine otolith thin section was carried out. The main aim of such exercise was to increase the agree-ment among readers and to highlight differences due to the interpretation criteria adopted, or due to the differences in the growth pattern among areas. There were two criteria for interpreting the anchovy and sardine daily Micro increments according to double bands (called GBR) or individual bands (IMR) form. The application of these criteria was recurrently discussed during the workshop, not being possible reach a unanimous agreement on standardization. So it was agreed to use the GBR in all areas, except for the Strait of Sicily and Adriatic Sea.
Another of the main issues of the workshop was to identify the position of the first annual ring (annulus) in the otoliths of these species, since it is one of the main sources of error that affect the precision of age. Based on different daily growth studies pre-sented at this workshop, the position of the first annual ring is validated on anchovy in the Bay of Biscay and the position of the first ring false or check is corroborated in the sardine of North Adriatic Sea, providing a series of recommendations to the annual ageing readers of these species.
A reference collection of otolith images was also provided for larvae and juveniles of anchovy and sardine from each area. Finally, a literature review of recent research re-lated daily growth of these species was performed and a new Workshop on Micro in-crement daily growth in European Anchovy and Sardine was proposed for 2017.