|Marine Resource Fact Sheet|
|Saithe - North Sea, Skaggerak, West of Scotland and Rockall, 2012|
|Saithe in Subarea IV (North Sea) Division IIIa (Skagerrak) and Subarea VI (West of Scotland and Rockall)|
|Considered a single stock: Yes
Spatial Scale: Sub-Regional|
Management unit: Yes
Habitat and Biology
Depth zone: Shelf (50 m - 200 m). Vertical distribution: Demersal/Benthic.
The juveniles (ages 0–2 years) generally occur in shallow coastal areas where they are protected from large fisheries. The fish are long-lived (20+ years) and tend to form large aggregations to a higher extent than for instance cod. Saithe starts to mature at age 4 (15% mature) and at age 7 all fish can be regarded as being mature. Environmental influence on the stock
A decrease in the mean weight-at-age has been observed since the mid-1980s, but this trend has now been reversed. Current information is insufficient to establish whether these reductions are linked to changes in the environment. There is no indication that the observed decline in weight-at-age is density dependent.
Jurisdictional distribution: Shared between nations
Water Area Overview
Spatial Scale: Sub-Regional
Ecoregion: North Sea
Considered a single stock: Yes
Saithe in the North Sea are mainly taken in a directed trawl fishery in deep water along the Northern Shelf edge and the Norwegian Trench. Analyses show a substantial shift in the Norwegian and German trawlers’ fishing pattern after 2008, both in time and spatial distribution. The importance of the fisheries on the spawning aggregations in the first quarter of the year has declined.
Effects of the fisheries on the ecosystem
||Catch 2011 = 97 kt, of which approximately 95% are taken by bottom trawl and 5% by other gears. Discards are low.
Hiddink et al. (2006) estimates that in areas of bottom trawl activity in the North Sea, benthic biomass and production is reduced by 56% and 21%, respectively, compared with an unfished situation. North Sea saithe fisheries are known to have less impact on the seafloor than most other bottom trawl fisheries.
ICES advises on the basis of the EU–Norway management plan that landings in 2013 should be no more than 100 684 tonnes for the whole assessment area.
Overall Assessment Results
Assessment ModelQuality consideration
Age distribution of Norwegian catch data has been revised substantially for 2010, which influences the biomass estimate in the whole assessment. Conflicting signals between the scientific surveys have become more apparent. All scientific surveys on adults have shortcomings in depth range (IBTS-Q3) or coverage (NORACU). Catches from older age classes in the surveys are not representative and therefore commercial cpue indices are used for tuning. Catch sampling data from the Norwegian fishing industry should be improved.
|Figure 18.104.22.168 Saithe in Subareas IV and VI, and Division IIIa. Historical assessment results (final-year recruitment estimates included). The 2010 assessment is not included since this was only a forecast based on the 2009 assessment. |
||Age-based assessment model (XSA).
||Three survey indices (NORACU, IBTS-Q3, NORASS);
||three commercial indices (FRATRB_VI, GER-OTB_IV, NORTR_VI2).
|Discards and bycatch
||Not included in the assessment.
||Benchmarked in January 2011 (revised in October 2011).
Management unit: YesManagement plans
The EU–Norway agreed management plan as updated in December 2008 (Annex 6.4.12) was evaluated by ICES (ICES, 2008), and considered to be consistent with the precautionary approach in the short term (< 5 years).
Biological State and Trend
Exploitation rate: Below limit
Abundance level: Above trigger
Source of information
The above excerpts are from the first two pages of the ICES advice, the supporting information to this advice can be read in full at the following reference:
ICES. Saithe in Subarea IV (North Sea), Division IIIa (Skagerrak), and Subarea VI (West of Scotland and Rockall). Report of the ICES Advisory Committee, 2012. ICES Advice, 2012. http://www.ices.dk/committe/acom/comwork/report/2012/2012/sai-3a46.pdf