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- Bryhn, Andreas, et al.
(författare)
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Kunskapsunderlag om möjliga icke-torskfiskerelaterade åtgärder för att torskbestånd ska bevaras och återhämta sig i svenska vatten
- 2020
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Rapport (refereegranskat)abstract
- Torsk (Gadus morhua) är en viktig art för marina ekosystem i Sverige, där den har en strukturerande och reglerande funktion i relation till andra arter. Torsken har under historiens gång även spelat en viktig roll för samhället i Sverige inom dess nuvarande gränsers område (Bohuslän har t.ex. inte alltid tillhört Sverige), som en målart för fiske. Samtliga torskbestånd som återfinns i havsområdena runt Sverige har nu dålig status och det internationella havsforskningsrådet ICES rekommenderar låg eller ingen fångst, beroende på bestånd. Utöver riktat fiske påverkas dock torsken av en rad andra faktorer som exempelvis bifångster i annat fiske, syrebrist, klimatförändringar, predatorer, parasiter, bottenpåverkan av trålning, förlust av uppväxtmiljöer, födobrist, tiaminbrist och giftiga ämnen. Denna rapport diskuterar möjligheter att skydda och bevara torsken på sätt som kan komplettera begränsningar i det riktade torskfisket. Torskens situation är komplex och rapporten är därför skriven utifrån ett ekosystemperspektiv för att möjliggöra en bredare ansats i förvaltningen av torskbestånd i svenska vatten, där alla relevanta påverkansfaktorer bör beaktas. Det bör poängteras att denna rapport inte har gjort någon ny utredning av påverkansfaktorernas effekter, utan har istället gjort en litteratursammanställning och en kvalitativ analys. Vi har ändå valt att lyfta fram vissa åtgärder som särskilt potentiellt betydelsefulla - en samlad kvalitativ expertbedömning som rangordnar olika åtgärders effektivitet för återuppbyggnad per bestånd, se avsnitt 6 i rapporten.
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| 3. |
- Bryhn, Andreas, et al.
(författare)
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Which factors can affect the productivity and dynamics of cod stocks in the Baltic Sea, Kattegat and Skagerrak?
- 2022
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Ingår i: Ocean and Coastal Management. - : Elsevier BV. - 0964-5691 .- 1873-524X. ; 223
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Forskningsöversikt (refereegranskat)abstract
- Stocks of Atlantic cod (Gadus morhua) in the Baltic Sea, Kattegat and Skagerrak (N. Europe) have been strongly exploited for decades bringing them into an enduringly depleted status. Scientific cod stock related advice for targeted and mixed fisheries is provided on an annual basis by the International Council for Exploration of the Sea. This advice forms a basis for ministerial decisions on, e.g., the total allowable catch and management plans. Despite measures to reduce fishing-induced mortality of cod, such as catch and effort restrictions, increased gear selectivity, closed areas and seasons, clear signs of recovery are yet to be seen. Thus, traditional advice for the management of these stocks may have to be complemented by advice on supporting measures focusing on other pressures hampering the recovery of cod. The present study elaborates on potential supportive measures for cod stock recovery in the Baltic Sea, Kattegat, and Skagerrak (including local populations where applicable), based on current knowledge. The list of measures presented here is the outcome of in-depth discussions on the state-of-the-art knowledge, among cod experts and further with stakeholders with the aim to follow principles of ecosystem-based fisheries management. Following the identification of different pressures on and prerequisites for the separate stocks, the listed measures differ between stocks and include cod bycatch mortality reduction, alterations in fisheries affecting food sources for cod, restocking, protection of juvenile habitats, and reduced predation. The literature review and the list of measures are intended to provide decision-support for managers and policymakers aiming to provide conditions for the cod stocks to recover.
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| 4. |
- Börjesson, Patrik, et al.
(författare)
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Occurrence of sharks, rays and rabbit fish in the Greater North Sea – and catches in Swedish fisheries
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report was written in response to a request from the Swedish Agency for Marine and Water Management to update an earlier technical note from SLU Aqua “Occurrence of skates and rays in northern European waters and catches in Swedish fisheries in the Skagerrak/Kattegat and the eastern North Sea”. The aim was to provide a comprehensive overview of elasmobranchs present in Swedish waters and to what extent these species are caught in Swedish fisheries. To describe the occurrence and spatial distribution of sharks, rays and rabbit fish we used fisheries-independent survey data from 1967–2020, as well as data from the national on-board observer program and official landing data. During this time a total of 21 species of sharks, rays and rabbit fish were reported from the Skagerrak, Kattegat and the Sound. Seven of the species were common in both the fishery independent and the commercial data supporting that they are native to Swedish waters. These species included three shark species; velvet belly (Etmopterus spinax), lesser spotted dogfish (Scyliorhinus canicula) and spurdog (Squalus acanthias); three species of rays; starry ray (Amblyraja radiata), thornback ray (Raja clavata), and sailray (Rajella lintea); and the rabbit fish (Chimaera monstrosa). The round ray (Rajella fyllae) was also relatively common in survey catches from the deeper parts of the Skagerrak. All common species were present year round, but spurdog also showed a seasonal trend, being more common along the Norwegian coast and in offshore part of the Skagerrak in the first quarter, and closer to the Swedish coast in the third and fourth quarter. There are no longer any targeted fisheries for elasmobranchs by Swedish vessels but by-catches occur, predominantly in demersal trawl fisheries in the deeper parts (> 200 m) of Skagerrak and the Norwegian trench where a majority the observed hauls had by-catch of one or more species. Usage of a sorting device (grid) in the Nephrops and Pandalus trawl fisheries appear to reduce the amount of by-catches. Historical and anecdotal information suggest that by-catch of spurdog in gillnets could be significant, but as landing were prohibited in 2010, no data is available since then. Starry ray and spurdog represents > 75 % of the estimated total catch weight of shark and rays combined. More than 90 % of elasmobranchs was discarded, which is not surprising given that landing of spurdog, starry ray, common skate and thornback ray are prohibited in 3a. Sailray is the only species landed to some extent (few tonnes per year) by Swedish vessels during the last five years. Swedish landings of sailray mainly come from the Pandalus fishery and from demersal trawl fishing without grids in the deeper parts of Skagerrak.
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