The ICES Working Group on Elasmobranch Fishes (Co-chairs, Samuel Shephard, Ireland and Paddy Walker, Netherlands) was held at IPMA, Lisbon, Portugal from 31st May to 7th June 2016.
Twenty-six Expert Group members attended, with five other members contributing via correspondence. One representative of the ICES Secretariat also attended the meeting. Nine ICES Member States were represented at the meeting, and a further two were represented by correspondence.
ICES WGEF meets annually, with advice for a subset of stocks drafted in alternating years. Work in 2017 focused on those stocks for which it was an advisory year: (i) skate stocks in the North Sea ecoregion; (ii) skate stocks in the Azores and MAR; (iii) catsharks (Scyliorhinidae) in the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast ecoregions; (iv) smooth-hounds in the Northeast Atlantic and (v) tope in the Northeast Atlantic.
Twelve Working Documents were presented to the Group, mainly relating to either recent results from fishery-independent trawl surveys, or from national projects to better understand the stock dynamics and biology of assessed species.
Some of the data used this year were submitted following the ICES Data Call. WGEF concluded that the format of the 2017 Data Call was more successful than the previous year, and enabled recent landings data for all elasmobranchs to be collated in a common format. Discard data for selected stocks were also made available following the advice of the Workshop on Discards (ICES 2017). Data checks of some national data were undertaken prior to the meeting, following the guidance developed during WKSHARKS 2016, with further data checks undertaken during the meeting. Whilst much progress was made towards developing a single source for estimated elasmobranch landings, data checks focused on those stocks being addressed in 2017 and further examination and data checks for more generic landings categories are ongoing.
Skates in the North Sea ecoregion and the Azores and MAR were assessed mostly using time series data from fishery-independent trawl surveys, with species-specific landings data also used when developing advice. Fishery-dependent data, such as DCF length sampling, effort data and landings information were the main data sources considered for those species for which fishery-independent data are limited or lacking.
Assessments were also carried out for catsharks (Scyliorhinidae) in the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast ecoregions, as well as smooth-hounds in the Northeast Atlantic and tope in the Northeast Atlantic.
Whilst there have generally been improvements in national species-specific reporting of elasmobranch landings, there is still uncertainty as to the quantities being discarded and the proportion of these that may be dead. A workshop on elasmobranch discards was held in Nantes in February 2017 and is reported in the Introduction.
WGEF also addressed ToRs on a proposed joint meeting with ICCAT for the assessment of the thresher shark (Alopias vulpinus); and updating life-history parameters for elasmobranchs.
Another ToR was to estimate appropriate MSY proxies. Most of the ray stocks in the ICES area are considered to be in assessment category 3, i.e., having reliable catch and survey data. In previous years, WGEF have assessed these stocks using only survey trends. In 2017, WGEF used two new data poor methods to conduct exploratory assessments for the following ray stocks:
- Thornback ray (Raja clavata) in Subarea IV and Divisions IIIa and VIId (North Sea, Skagerrak, Kattegat, and eastern English Channel): RJC–347d.
- Cuckoo ray (Leucoraja naevus) in Subarea IV and Division IIIa (North Sea, Skagerrak, and Kattegat): RJN–34.
- Cuckoo ray (Leucoraja naevus) in subareas 6 and 7 and divisions 8.ab and 8.d: RJN–678abd.
The first assessment approach applied the WKLIFE set of length-based indicators (LBI) to screen the length composition of catches and classify the three ray stocks according to conservation and sustainability, yield optimization and Maximum Sustainable Yield (MSY) considerations. The Surplus Production in Continuous Time (SPiCT) model (Pedersen & Berg, 2017) was then also applied to provide estimates of biomass, fishing mortality and MSY. These exercises were informative, highlighting the need to adjust LBI and associated reference points (RP) to account for elasmobranch life history and fisheries dynamics. The SPiCT modelling was also encouraging, providing assessment outputs with surprisingly low uncertainty. WGEF considers that there is scope in the future to move some of the category 3 skate and ray stocks into category 2.