Stocks under WGDEEPs remit include the roundnose grenadier, black scabbardfish and orange roughy, which complete their life cycle at great depth as well as species occurring both on shelf areas and in deep waters such as ling, greater forkbeard and blackspot seabream. The latter species even occurs in very coastal and estuarine habitats at juvenile stages. Assessed stocks occur throughout the ICES areas from Nordic Seas (Norwegian Sea, Barents Sea, Icelandic and East Greenland waters) to the Gulf of Cadiz and the Azores. Further to assessing stocks, WGDEEP analyses the status of bycatch species and deep-sea fish communities.
The scientific purpose of WGDEEP includes performing quantitative stock assessments on stocks such as the roundnose grenadier and blue ling in Faroese waters and the west of the British Isles as well as ling, blue ling, and tusk in Icelandic waters. However, a number of stocks under the group’s remit are data-limited ones which are assessed based on trends in indicators such as survey indices and commercial catch per unit of effort (cpue). These assessments, both quantitative and based on trends, are then used by ACOM as the basis for advice.
ICES advice for WGDEEP stocks is currently delivered biennially, the rationale being both the species’ life history, which is broadly characterized by moderate to low biological productivity that cannot generate rapid change in stocks status and also data limitation. Nevertheless, this does not apply to all of the stocks assessed such as tusk, ling and greater silver smelt. Similarly owing to the lengthening of time-series, the increasing data collection performed by the EU Data collection framework, national programmes, and scientific projects the amount of data available to WGDEEP has been increasing strongly in recent years; and this has meant the possibility of better quantitative advice.
As with all assessment working groups, there is a set of Generic Terms of References (ToRs) which come from ACOM and form the basis of WGDEEP. However, there are also a number of special requests from the European Commission and ICES Member Countries as well as from the North East Atlantic Fisheries Commission (NEAFC) and other clients, mostly about the impacts of deep-sea fisheries on the environment and Vulnerable Marine Ecosystems (VMEs) such as cold-water coral and deep-sea sponge aggregations.
WGDEEP is a relatively new expert group, originally forming in 1994 as a study group. Over time the group’s objectives and stocks have varied, in particular with deep-sea sharks having been passed to the Working Group on Elasmobranch Fishes (WGEF). Some WGDEEP scientists are also members of WGDEC and WGEF. Owing to the strong scientific interest in the deep ocean over the past decade, overall knowledge rose sharply triggering rapid progress in WGDEEP stock assessment methods and all the ecosystem aspects that the group can address.