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Witch sole, Northern stock, demersal trawl

fish

Content last updated
16th Feb 2017

Stock:

Management:

Overview

Witch sole or witch flounder (Glyptocephalus cynoglossus), is a right-eyed flounder of the family Pleuronectidae which occurs on both sides of the Atlantic Ocean. The species is mainly found on soft bottoms, mostly clay or clean sandy bottoms between 100–400 m depth. The main diet consists of crustaceans, worms, brittle stars and fishes.

Witch sole is typically a bycatch species, mostly captured in bottom otter trawls (88%) targeting whitefish (such as cod and haddock), or other flat fish species such as plaice, etc. It is also an important bycatch species in some Nephrop fisheries.

Stock Status

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The status of the witch flounder stock in Subarea IV and Divisions IIIa and VIId (North Sea, Skagerrak and Kattegat, Eastern English Channel) has been scored a moderate risk. This is because the species has low resilience to fishing exploitation (FishBase, 2015) and the stock abundance has shown a marked increase in the last couple of years. No biomass or fishing mortality reference points have been defined for this data-limited stock, and therefore cannot be used to derive a risk score. Instead, a risk score was calculated using a data-limited approach where the low resilience of lemon sole to fishing exploitation was weighted by an increasing population trend.

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Management

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The management of witch flounder in Subarea IV (North Sea) and Divisions IIIa (Skagerrak–Kattegat) and VIId (Eastern Channel) has been scored a moderate risk. This is because data-limited approaches are used for setting management controls. No specific management controls have been established to restrict harvesting, and no stock-specific TAC has been defined by the European Commission. A TAC combining lemon sole and witch sole may not be an appropriate management measure to control the harvest rates of bycatch species.

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Bycatch

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The bycatch risk of witch flounder in Subarea IV (North Sea) and Divisions IIIa (Skagerrak–Kattegat) and VIId (Eastern Channel) has been scored a high risk. This is because demersal fisheries operating in these areas discard on average between 10 and 40% of the catch in weight. Demersal trawls are an active form of fishing gear that have the potential to take relatively high quantities of bycatch in certain circumstances.

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Habitat

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The habitat risk of this fishery has been scored a high-moderate risk. Although otter trawls are considered to have potential to cause significant habitat damage, damage to vulnerable and sensitive marine habitats is likely to be minimised given that the footprint of the fishery is within core areas, of historically fished ground. However, spatial management to reduce potential interactions with vulnerable habitats are being developed, as there remains uncertainties about the location of some sensitive seabed habitats so these remain at risk.

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Outlook

Type Current Risk Status Outlook Reason

Stock

Moderate Stable

The status of the stock is likely to remain stable in the future given that no major changes in stock status are anticipated.

Management

Moderate Stable

The management of the stock is likely to remain stable in the future. The CFP is going through reform and there is some uncertainty on how this will impact fisheries management in the North Sea, particularly due to the introduction of a landings obligation.

Bycatch

High Improving

Bycatch in this fishery is relatively high. However, with technical and spatial management measures continuously under development and the incoming EU landings obligation intended to reduce discarding of managed species, the bycatch risk is likely to reduce in the future.

Habitat

High Improving

Otter trawls have the potential to affect seabed habitats, but spatial management measures are continuously being developed and will likely reduce the risk. As planned networks of Marine Protected Areas become established, larger areas of sensitive habitat will become protected from trawling.

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