Working Group on the Biology and Assessment of Deep-sea Fisheries Resources (WGDEEP)

Other titles Groupe de travail sur la biologie et l'évaluation des ressources des pêcheries profondes (WGDEEP)
Type Article
Date 2019
Language English
Ref. ICES Scientific Reports. 1:21
Author(s) ICES
Contributor(s) Lorance PascalORCID
Source ICES Scientific Reports/Rapports scientifiques du CIEM (2618-1371) (ICES), 2019 , Vol. 1 , N. 21 , P. 988p.
DOI 10.17895/

WGDEEP gives advice according to an advice schedule where, in short, half of the stocks advice is given in year y and the other half has advice in year y+1. The exception from this schedule is stocks from ICES Division 5.a (Iceland) that have advice annually. Available time-series for international landings and discards, fishing effort, survey indices and biological information were updated and for all stocks and are presented in Sections 4–15 of the report.

In response to a special request from the EU on the added value of having small TAC for greater silver smelt in subarea 7 the meeting evaluated available information. The EU TAC, currently covering subareas 5, 6  and 7, does not correspond to the stock unit evaluated by ICES which is greater silver smelt in subareas 7, 10, 12 and Division 6b. The current ICES advice recommends to limit catch to a low level. Possible  seasonal aggregations of greater silver smelt in the North of Subarea 7 should be considered as extension of the more abundant stock from divisions 5b and 6a. In the absence of a TAC of greater silver smelt in Subarea 7, the potential risk is the development of target fishing on possible aggregations. To prevent this the fisheries should be monitored carefully so that TAC, or similar management action, can be reintroduced on short notice in case of very rapid increase in catches as has been observed in other greater silver smelt fisheries. Bycatch of GSS in other fisheries should be kept at absolute minimum. A mechanism based on a maximum proportion of bycatch of greater silver smelt per fishing operation and in the total catch could be considered. Some other important topics were discussed in the meeting and require further scientific  studies, being sorted out through appropriate ICES protocols or a combination of both. The first of these topics was how advice could be designed as precautionary in the event of an extended recruitment

failure, as seen for blue ling in sections 5.a and 14, 2. The second topic was how to treat regional differences in biomass/catch/survey trends in regions of a large stocks unit as seen for ling in Subareas 6–9, 12, and 14, and Divisions 3.a and 4.a (lin.27.3a4a6-91214). For this assessment unit, the bulk of landings are from divisions 4.a and 6.a where commercial CPUE show an increasing biomass trend while in Subarea 7, catch have declined over the past 3 decades and one survey covering a significant part of Subarea 7 shows a strongly decline index of biomass of ling. The group discussed that there may be some population structure that differs from the assessment unit, and that changes in environment factors may impact ling differently in different parts of its distribution.

Contrasting trends were observed for stock with a biomass index from surveys, stock with clear variation in indices were:

  • Greater silver smelt in area 1, 2, 3a and 4: based upon the acoustic index, the biomass of has slightly decreased, but an issue that needs addressing is marked increased bycatches in other fisheries in area 4. These are registered in the Norwegian catches as lesser silver smelt. The lesser silver smelt has a more southern distribution than greater silver smelt and the distribution areas overlap in the North Sea. Distribution may change as a response to changes in environment. Still, available information suggests that this bycatch is predominantly greater silver smelt, and they have been treated as such in the assessment. This issue is planed to be addressed further in the upcoming Benchmark for the stock in 2020

  • Greater silver smelt in Divisions 5.b and 6.a: the biomass index also decreased for leading to a reduction in advised catch using the DLS 3.2 rule as usual. The advised landings decreased by 20% according to a decrease in the Faroese summer groundfish survey index, which is used as the index for the stock development. It has to be noted that this survey have very few stations (<5) deeper than 500 m and are therefore only likely to cover the juveniles adequately. The adult part of the population is not fully covered by these surveys and they may not necessarily reflect correctly the temporal variation of the biomass of the stock. This stock unit is planned to be benchmarked in February 2020.

  • Ling in Division 5.b: a decrease in the Faroese summer groundfish survey index, which is used as the index for the stock development occurred in 2017-18 and lead to advising 20% reduction of catch. Even if all signs from commercial catches indicate that ling in Division 5.b at present is in a good state, and this is confirmed in the exploratory age based assessment and length-based indicator method. This stock unit is suggested to be benchmarked in 2021.

  •  Blackspot seabream in Subarea 10: for this stock the biomass index increased to high level in recent years. Possibly as a results of several management measures introduced in recent years.

The stocks of greater silver smelt in the NE-Atlantic are planned for ICES Benchmark in February 2020.

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