Flounder

Platichthys flesus

Method of production — Caught at sea
Capture method — Beam trawl
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea
Stock detail — IIIa, IV
Picture of Flounder

Sustainability rating three info

Sustainability overview

Flounder is mainly a bycatch species in bottom trawl fisheries for North Sea plaice and sole. They are mostly discarded due to their low commercial value and poor market demand, with discard rates in the order of 28- 46% of the total catch. Avoid eating immature fish (less than 25cm) and fresh fish caught during the spawning season (February-May in the North Sea). In Cornwall, North-Western England & North Wales Inshore Fisheries Conservation Authorities (IFCAs), landing flounder below 25cm is prohibited. Choose fish from these areas where available. As an under-utilised species it is ranked by Cefas as one of the most tolerant of over-fishing and therefore one of the better ones for consumers to eat.

Biology

A widespread European fish found in both fresh and marine water. Flounder is a coastal species that divides its life cycle between brackish and freshwater habitats. It moves offshore into deeper water of higher salinity in winter where it spawns in the spring. Spawning takes place at depths of 20-50 m in the southern North Sea from February to May. Males become sexually mature when 2-3 years old (20-25 cm) and females when 3-4 years old (25-30 cm), but in the northern part of the range this may occur some 1-2 years later. After spawning they migrate to inshore and sometimes brackish waters. The shallow coastal zone, and in particular the Wadden Sea, are important nursery areas. Like plaice, they spend most of the day buried in the sand, but become very active at night and move into shallower water to feed. Flounder attains a length of 50-60 cm and can live up to 15 years. The species feeds on a wide variety of invertebrates and fish in some areas.

Stock information

Stock Area

North Sea

Stock information

Flounder is a species moderately vulnerable to over-exploitation. The North Sea is the main area for the fishery where the bulk of the landings are taken. Assessment of the stock is based on survey trends. Landings have been decreasing since 2006 and are stable in the most recent years. The available survey information indicates no clear trend in stock biomass. Landings data is not however indicative of catches since discard rates are variable (28-46%).
Flounder is considered an under-utilised species. Under-utilised species are ones that fishermen don't catch their full quota of, or they catch them but then discard the fish because no one wants to buy them. CEFAS have compiled a list of these species using quota and discard information, expert advice and local knowledge and chose around 50 under-utilised species to study. To determine their sensitivity to over-fishing CEFAS has developed a system, the Relative Life History Sensitivity Analysis, to study the risk. It uses biological information like growth and breeding strategies to see how increased fishing pressure might damage each species. They then ranked the species by how tolerant they are to being over-fished. For a full list of the species that are most under-utilised AND most tolerant of over-fishing and therefore the best ones for consumers to consider choosing see www.cefas.defra.gov.uk/our-science/fisheries-information/marine-fisheries/under-utilised-species.aspx
ICES advises that when the precautionary approach is applied, catches should be no more than 6274 tonnes in each of the years 2018 and 2019 (5,228 tonnes in each of the years 2016 and 2017). If discard rates (38%) do not change from the average of the last three years (2014-2016), this implies landings of no more than 3890 tonnes.

Management

There are no specific management objectives for this species. There was a joint total allowable catch (TAC) for dab and flounder in the North and Norwegian Seas. However, scientists were concerned that management of dab and flounder under a combined species TAC prevented effective control of single species exploitation rates and could potentially lead to over fishing of either species. ICES was further concerned that TACs might not be an appropriate management tool for bycatch species such as flounder. ICES was therefore requested to assess the risk to the stocks of dab and flounder of having no catch limits for these stocks. ICES have advised that the risk of having no catch limits for the stocks of dab and flounder is currently considered to be low and not inconsistent with the objectives of the Common Fisheries Policy as long as dab and flounder remain largely bycatch species, with the main fleets catching dab and flounder continuing to fish the target species (plaice and sole) sustainably within the FMSY ranges provided by ICES. Consequently, the combined TAC for dab and flounder for Subarea 4 and Division 2.a was removed by the European Commission Council Regulation (EU) 2017/595 in March.

Capture Information

Flounder is not an important food-fish and not commonly targeted commercially. It is taken as bycatch in fisheries for demersal and flat fish, mainly in beam trawl (86%) fisheries for plaice and sole. There is potential damage to the seabed from trawling, especially so when using beam trawls. Trawling is also associated with discarding of unwanted fish, i.e. undersized and/or non-quota and/or over-quota species. No minimum landing size is specified for this species in EU waters. In Cornwall and North-Western England & North Wales Sea Fisheries Districts, landing flounder below 25cm is prohibited. In the Southern IFCA a MLS of 27cms is enforced. Flounder matures between 20-30cm, landing fish below this size will not protect 100% of the juveniles and many will be caught before they have matured and spawned.

Alternatives

Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.

Dab
Halibut, Atlantic (Farmed)
Halibut, Pacific
Megrim
Plaice
Sole, Dover sole, Common sole
Turbot (Farmed)

References

EU. 2017. COUNCIL REGULATION (EU) 2017/595 of 27 March 2017 amending Regulation (EU) 2017/127 as regards certain fishing opportunities. Official Journal of the European Union, L 81/6. http://eur-lex.europa.eu/legalcontent/EN/TXT/PDF/?uri=CELEX:32017R0595&from=EN
ICES Advice 2017 http://ices.dk/sites/pub/Publication%20Reports/Advice/2017/2017/fle.27.3a4.pdf
STECF. 2016. Fisheries dependent information. Scientific, Technical and Economic Committee for Fisheries (STECF-16-20). Publications Office of the European Union, Luxembourg. EUR 27758 EN. doi 10.2788/502445.