Working Group on Elasmobranch Fishes (WGEF)
ICES WGEF meets annually and is responsible for providing assessments and advice on the state of the stocks of sharks, skates, and rays throughout the ICES area. In 2020, WGEF provided advice for 28 stocks of rays and skates distributed in two ecoregions: the Celtic Seas and the Bay of Biscay and Iberian coast. Only one stock of shark, spurdog (Squalus acanthias) was subject to advice this year.
Strong improvements in the quality of data used by WGEF have been made in recent years and continued in 2020. The quality of landings data was historically poor for several reasons including that landings were not reported on a species specific level as these are subject to taxonomical confusions. Despite improvements of reported landings in the past decade, quality check and error corrections, reliable time-series of landings do not span more than 10–12 years for most stocks. Estimated discards are uncertain because elasmobranchs are mostly bycatch in small amounts in all types of fisheries. Further, survival of discarded elasmobranchs is thought to be high but quantitative estimates are scarce so that the relationship between discards and dead catches is unknown. As a consequence, for numerous stocks it is not possible to provide catch advice. For those stocks, advice on landings is formulated. With the exception of spurdog, for which an analytical assessment is available, many assessments are based on survey trends only. Trends are derived for scientific surveys, which are considered providing the most reliable data on elasmobranch stocks, whilst for a few stock of the Iberian coast, advice is based on biomass trends derived from catch per unit of effort from commercial fisheries. Also, a part of the stocks cannot be assessed yet. These stocks are classified as ICES category 5 and 6 stocks for which even survey data are lacking and only (minor) landings or some bycatch data are available.
For rays, no assessment was done for 9 out of 15 stocks in the Celtic Seas and for 6 out of 12 stocks in the Bay of Biscay and Iberian stocks. For these stocks advices are only based on landings or catches according to the ICES precautionary approach. In the Celtic Seas, among the six stocks of rays for which the trend in biomass could be estimated, this trend was increasing for two stocks (rjc.27.7afg, rju.27.7de), decreasing for two (rje.27.7fg, rjm.27.67bj) and stable for the last two (rjm.27.7ae-h, rjc.27.6). In the Bay of Biscay and Iberian coast, among the six stocks of rays for which the trend in biomass could be estimated, this trend was increasing for five stocks (rjh.27.9a, rjn.27.8c, rjn.27.9a, rjm.27.8, rjc.27.9a) and stable for one (rjc.27.8). Stocks in ICES cate-gory 5 include spotted ray in the Atlantic Iberian waters (rjm.27.9a), for which recent survey data were missing. Lastly, one stock straddles the two ecoregions (rjn.27.678abd) and had an increasing trend while the assessment of spurdog suggests an increase in biomass of this stock, which is also reflected in some surveys as shown in the report.
The high proportion of stocks for which the trend cannot be estimated, imply that more data and further work is needed to better monitor rays stocks. Some of this work is scheduled in the WKSKATE workshop to be held in November to evaluate which surveys and indicators are suitable to assess and deliver advice for elasmobranch stocks.
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