Fishery Resources Monitoring System

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Salmon - Main basin and Gulf of Bothnia, 2012
Marine Resource  Fact Sheet
ICES Advice 2012
Salmon - Main basin and Gulf of Bothnia, 2012
Fact Sheet Citation  
Salmon in Subdivisions 22 - 31 (Main Basin and Gulf of Bothnia)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Atlantic salmon, fr - Saumon de l'Atlantique, es - Salmón del Atlántico, zh - 大西洋鲑, ru - Лосось атлантический (=семга)
Geographic extent of Salmon - Main basin and Gulf of Bothnia
Main Descriptors
Considered a single stock: No        Spatial Scale: Sub-Regional
 
 
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Demersal/Benthic.  


The Atlantic salmon Salmo salar colonized the Baltic Sea by at least three glacial lineages, today represented by salmon in the Gulf of Bothnia, southern Sweden, and the southeastern Baltic Sea including the Gulf of Finland. The salmon reproduce in rivers across the whole Baltic Sea, but the most productive rivers are found in the Gulf of Bothnia. Juvenile salmon stay in the freshwater stream for one to four years and then spend one to several years at sea on a feeding migration before they return to spawn in the natal river. Salmon from different rivers (populations) are mixed in the southern Baltic during the feeding migration, but they become gradually segregated on their migration routes back to the home rivers. The Baltic salmon feed mainly on herring and sprat during the sea migration.

Environmental influence on the stock
Geographical Distribution
Jurisdictional distribution: Shared between nations

Water Area Overview
Spatial Scale: Sub-Regional


Ecoregion: Baltic Sea
Geo References
Resource Structure
Considered a single stock: No
Exploitation
 

The fisheries


The nominal catch in the whole Baltic Sea (Subdivisions 22–32), including rivers, has declined from 5636 tonnes in 1990 to 934 tonnes in 2011 (Table 8.4.14.1). The nominal catch in numbers is presented in Tables 8.4.14.1 and 8.4.14.3. Only 49% of the TAC of salmon in Subdivisions 22–31 was utilized in 2011 (Table 8.4.14.4). The nominal catch in the offshore fishery in 2011 was similar to 2010. Preliminary data for 2011 indicate that catches in the coastal fishery were also similar to 2010, whereas river catches increased compared to 2010, particularly when expressed in weight (Table 8.4.14.4). The share of different fisheries (including also discard, unreporting, and misreporting) in the total catch during 2001–2011 is illustrated in Figure 8.4.14.5.

The salmon fishery has changed considerably since the beginning of the 1990s. The very high exploitation rate in the offshore and coastal fisheries has decreased successively due to e.g. 1) regulatory measures such as closed areas and changes in the opening time of fishery, 2) marketing restrictions on large salmon in certain countries due to high dioxin level, and 3) increased seal damage to catches and gear. The driftnet ban in 2008 decreased offshore catches in 2008 to the lowest value recorded since 1972. However, changes in the application of dioxin regulations in 2009, increases in market price for salmon, and reduced opportunities for income in other fisheries have resulted in an increase in offshore fishing effort after 2008. Despite the changes in dioxin regulations, the existing marketing rules probably still suppress some of the fisheries, particularly in Denmark..
Catch distribution Total catch (2011) is 1.617 kt (whole Baltic Sea), where 60% are landings, 11% discards, and 29% unaccounted removals.



Effects of the fisheries on the ecosystem

The current salmon fishery probably has no or minor influence on the marine ecosystem. However, the exploitation rate on salmon may affect the riverine ecosystem through changes in species compositions. There is limited knowledge on the magnitude of these effects.
Assessment
 
Scientific Advice

ICES advises on the basis of the MSY approach a TAC of not more than 54 000 individuals of salmon. As the perception of the stock status has not changed markedly since last year’s assessment, the advice for the fishery in 2013 is the same as the advice given in 2011 for the 2012 fishery and, therefore, a decrease in exploitation with respect to the TAC implemented in 2012 is required.

The share of the total catch that is mis- and un-reported was estimated to be about 30% in 2011. Reducing these unaccounted removals would allow a higher TAC recommendation.

Salmon management should be based on the assessments of the status of individual stocks in the rivers. Fisheries on mixed stocks that cannot direct fishing only to those stocks that are close to or above their targets, present particular threats, and effort in such fisheries should be reduced. Fisheries in open-sea areas or coastal waters are more likely to pose these problems than fisheries in estuaries and rivers.

Salmon stocks in the rivers Rickleån and Öreälven in the Gulf of Bothnia, Emån in southern Sweden, and in a majority of the rivers in the southeastern Main Basin are especially weak and need longer-term stock rebuilding measures, including fisheries restrictions, habitat restoration, and removal of physical barriers. In order to maximize the potential recovery of these stocks, further decreases in exploitation are required along their feeding and spawning migration routes. The offshore fishery in the Main Basin catches all weak salmon stocks on their feeding migration. The coastal fishery catches weak stocks from northern rivers when the salmon pass the Åland Sea and Gulf of Bothnia on their spawning migration.
Assessment Model

Quality consideration


A considerable amount of total catches consists of estimated unreported catches (Table 8.4.14.3), which introduces uncertainties in the assessment. Catch per unit effort in the Polish offshore fishery and deviations in the reported species composition between Polish and other countries’ longline fisheries indicate large-scale misreporting of salmon as sea trout in the Polish fishery, and this misreporting constitutes a significant amount of the unreported catches (Table 8.4.14.3). However, there are some indications that the presented misreporting in the Polish fishery may be overestimated, especially in recent years. Internationally coordinated landing inspections are probably necessary to minimize the presumed substantial mis- and unreporting of catches in the offshore longline fishery.

Scientific basis


The assessment uses a Bayesian estimation procedure. This technique allows an explicit incorporation of prior knowledge (from previous studies, literature, and/or expert opinions) about parameters in the assessment. With this approach uncertainties about estimated quantities are formulated as probability distributions.

The estimation of potential smolt production capacity is based on expert knowledge (prior information) and the spawner/smolt estimates (river-specific stock–recruit relationships) which are derived by fitting the assessment model with various data. The model incorporates new information annually and, thus, updates both smolt production historically and the potential smolt production capacity for each river. Inclusion of new information causes annual changes in these as well as in other parameter estimates.
Working group report WGBAST
Biological State and Trend
Exploitation rate: Undefined
Abundance level: Undefined
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. Salmon in Subdivisions 22–31 (Main Basin and Gulf of Bothnia). Report of the ICES Advisory Committee, 2012. ICES Advice, May 2012. Click to openhttp://www.ices.dk/committe/acom/comwork/report/2012/2012/sal-2231.pdf
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