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Herring - Bothnian Bay
Marine Resource  Fact Sheet
ICES Advice 2012
Herring - Bothnian Bay
Fact Sheet Citation  
Herring in Subdivision 31 (Bothnian Bay)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Atlantic herring, fr - Hareng de l'Atlantique, es - Arenque del Atlántico, ru - Сельдь атлантическая
Geographic extent of Herring - Bothnian Bay
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: No        Reference year: 2012
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateUndefinedUncertain/Not assessed
Abundance levelUndefinedUncertain/Not assessed
Figure 8.4.7.1
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Pelagic.  


Growth for this stock is limited by environmental conditions and biotic factors such as competition for prey. The mean weight-at-age decreased in the 1990s from high values in the 1980s and has continued to be low. This variation over time in weight-at-age is very similar to that of herring in the Bothnian Sea. The main predators on herring are ringed seal and grey seal.

Environmental influence on the stock

Environmental conditions in this area are extreme for herring. Low salinity (1–3%), long winters, prolonged ice periods, and cool summers affect the growth. Environmental conditions seem to determine the recruitment. For example, the strong year classes of 1988, 1999, 2002, and 2006 hatched during very warm summers.
Geographical Distribution
Jurisdictional distribution: Shared between nations

Water Area Overview
Spatial Scale: Sub-Regional


Ecoregion: Baltic
Geo References
Resource Structure
Considered a single stock: Yes
Exploitation
 

The fisheries


Fluctuations in total trawl catches and the length of the fishing season depend on the onset of winter and the ice cover in the autumn. Normally, the trawl fishing season starts in late April and ends in late May to July. The trawl fishery starts again in August/September. The ice cover usually appears in early November. Sprat bycatches in herring fisheries are very small, as sprat is found only occasionally in Subdivision 31.


Catch distribution Total catches (2011) 3350 t, where 100% are landings (94% trawls, 5% trapnets, and 1% gillnets).



Effects of the fisheries on the ecosystem

The main part of the catch is used for fodder; there is no unwanted bycatch. The proportion of other species is of minor importance; these include smelt (Osmerus eperlanus), vendace (Coregonus albula), whitefish (Coregonus lavaretus), and three-spined stickleback (Gasterosteus aculeatus).
Assessment
 
Scientific Advice

Based on the ICES approach for data-limited stocks, ICES advises that catches should be no more than 2100 tonnes.
Overall Assessment Results
Figure 8.4.7.1 Herring in Subdivision 31 (Bothnian Bay). Top left panel: Total landings (tonnes). Top right panel: Cpue in the trapnet fishery, regarded as representative for the variation of stock abundance over time. Bottom left panel: Effort by fishery, regarded as representative for the variation of fishing pressure over time.
Assessment Model

Quality consideration


The advice is based on cpue from trapnet, as an indicator of stock abundance. The uncertainty of these indices is not available.

The methods applied to derive quantitative advice for data-limited stocks are expected to evolve as they are further developed and validated. The harvest control rules are expected to stabilize stock size, but they may not be suitable if the stock size is low and/or overfished.

Scientific basis

Assessment type Cpue and effort analysis.
Input data Commercial fleet indices (pelagic and demersal trawl fleets and trapnet).
Discards and bycatch Negligible.
Indicators Mean weight-at-age of herring.
Working group report WGBFAS
Management
Management unit: No


Management plans


No specific management objectives are known to ICES. The EU manages fisheries on this stock in conjunction with those on the stock in Subdivision 30.
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. Herring in Subdivision 31 (Bothnian Bay). Report of the ICES Advisory Committee, 2012. ICES Advice, June 2012. Click to openhttp://www.ices.dk/committe/acom/comwork/report/2012/2012/her-31.pdf
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