Turbot in the Celtic Sea, Bay of Biscay and Iberian Coast, Gillnet
In the last decade, the total landings of turbot were between 5000 and 6500 t (ICES 2012) of which the English Channel and Celtic Sea only accounted for around 15%. Fishing grounds from where the landings represent on average between 2 and 5% of the total landings over the entire time-line are caught with in ICES divisions IIIa, IIIb-d, VIIa, VIII and IX.
Fisheries independent catch data for turbot are collected in the Irish Sea and the eastern channel beam trawl surveys although the data are too limited to detect any trends in recruitment or adult biomass.
Stock structure and recruitment
There is no clear genetic evidence in favour of one large biological stock or multiple separate stocks. However there is some genetic evidence for a break between the southern and Northern components. Turbot from the North Western Waters are genetically more similar to those from the southern North Sea.
Recruitment patterns are unknown for this area as very little comprehensive data is available.
Data gaps and research priorities
Because turbot is a Group 2 species under the EU Data Collection Framework, there are some issues limiting the availability to collect biological information. Turbot are caught commercially in relatively low numbers, and because of their high commercial value, it is very difficult to collect biological data in sufficient numbers for meaningful analysis.
The coverage of research survey is limited, and due to the inherent design of research vessel surveys (e.g. lower trawling speeds and shorter towing times, compared to commercial vessels), it is easier for bigger fish to escape the net, and hence more difficult to obtain information on larger (>30 cm) fish. (ICES, 2013).
Further multidisciplinary studies (e.g. genetic markers, tagging and comparative studies on fecundity) are required to formulate robust definitive advice for the stock structure of turbot.
ICES. 2012. Report of the Working Group on Assessment of New MoU Species (WGNEW), 5 – 9 March 2012, . ICES CM 2012/ACOM:20. 258 pp.
ICES 2013 Report of the Working Group on Assessment of New MoU Species (WGNEW), 18 – 22 March 2013. ICES CM 2013/ACOM:21. 189 pp