Capture method — Demersal otter trawl
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea, Skagerrak and Kattegat
Stock detail — 4, 3a
Updated: February 2020.
Dab is a bycatch species and commonly discarded due to its low commercial value and poor market demand, with discard rates in the order of 90% (about 40,545 tonnes in 2018!). The latest stock assessment undertaken in 2019 indicated that overfishing was not occurring (below FMSY proxy) and the biomass was not overfished (above the proxy for MSY Btrigger). Dab was previously managed under a combined total allowable catch (TAC) together with flounder, but this was recently removed following ICES advise indicating the risk of having no catch limits for the dab and flounder stocks was considered to be low and not inconsistent with the objectives of the Common Fisheries Policy (CFP). ICES stated this advice was valid as long as dab and flounder remained 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. If this situation was to change this advice would need to be reconsidered. Catches have been below levels recommended in the past and plaice and sole are currently fished within these ranges. Otter trawlers interact with the seabed and can modify bottom topography and cause damage and removal of some biogenic features including vulnerable marine habitats and benthic communities. They can also encounter occasional bycatch of vulnerable species.
Dab is a widespread demersal species on the Northeast Atlantic shelf and distributed from the Bay of Biscay to Iceland and Norway, including the Barents Sea and the Baltic. It is one of the most abundant demersal species in the North Sea, with its centre of distribution in the Southern North Sea. Dab is a right-eyed flatfish (both eyes are on the right side of the body) related to the plaice, flounder and sole. It can reach a length of about 40 cm and an age of 10-12 years. Spawns in January to August, earliest off Britanny and southern England, later in the North Sea (April to June) and in the Barents Sea (June-July). In the Baltic Sea they spawn in April-August. In the North Sea the males become sexually mature at 2-3 years when 10-20 cm long, the females at 3-5 years when 20-25 cm. Because of its sedentary nature, dab has proved to be a valuable indicator in eco-toxicological studies.
Criterion score: 0 info
North Sea, Skagerrak and Kattegat
The state of the stock in this region is indicative of trends only and proxy reference points have been applied. The latest stock assessment undertaken in 2019 by the International Council for Exploration of the Sea (ICES) indicated that overfishing was not occurring (below FMSY proxy) and the biomass was not overfished (above the proxy for MSY Btrigger). Dab is considered an under-utilised species. Under-utilised species are ones that fishers don’t catch their full quota of, or they catch them but then discard the fish because there is little market demand. The biomass has been increasing since the start of the time-series (2003), but has declined since its peak in 2016. Total mortality is fluctuating without trend and catches have ranged from 35,000 to 60,000tonnes. Recruitment showed an increasing trend until 2014, but has declined since then. ICES indicate that discard information is available for the years 2002-2018 for the most important fisheries. However, given the extremely high proportion of discards in the catch (91%), there may be uncertainty in the estimation of the total catch. Furthermore, survival rates of discards are unknown and there are no reliable data on discards are available for beam trawlers targeting brown shrimp. The discarding in these fisheries may have a considerable impact on the stock. ICES have not been requested to produce catch advice for this stock so there is no scientific catch advice for future years provided. However, it is noted that so long as the species in the targeted fisheries for which dab is a bycatch (mainly plaice and sole) are exploited sustainably (within FMSY ranges), there is a low risk of dab becoming overexploited. ICES note that if this situation changes the advice would need to be reconsidered.
Criterion score: 0.5 info
There are no specific management objectives for this species and management of dab in the North Sea is considered only partially effective. Dab is a bycatch species in other flatfish fisheries for plaice and sole and is generally considered underutilised and is commonly discarded due to low market value and demand. As a bycatch species, management under the EU North Sea Multiannual Management Plan (NSMAP) for demersal stocks (2018) applies. The NSMAP aims to ensure that exploitation of living marine biological resources restores and maintains populations of harvested species above levels which can produce the Maximum Sustainable Yield (MSY) and that the precautionary approach to fisheries management is applied. Bycatch stocks do not have specific targets under the NSMAP but are supposed to be managed in accordance with the best available scientific advice and the precautionary approach when no adequate scientific information is available.
Dab was previously managed under a combined total allowable catch (TAC) together with flounder, but this was recently removed following ICES advice in 2017 indicating the risk of having no catch limits for the dab and flounder stocks was considered to be low and not inconsistent with the objectives of the Common Fisheries Policy (CFP). ICES stated this advice was valid as long as dab remained largely bycatch, with the main fleets catching dab continuing to fish the target species (plaice and sole) sustainably within the FMSY ranges provided by ICES. If this situation changed this advice would need to be reconsidered. Catches have been below levels recommended in the past and plaice and sole are currently fished within FMSY ranges.
As dab is not subject to catch limits, it does not fall under the EU landing obligation and approximately 91% of the catch has been discarded in recent years and there is no official EU minimum conservation reference size (MCRS).
Criterion score: 0.5 info
In 2018, dab catches from otter trawling accounted for about 32% of the total catch. Bottom trawls disturb seabed habitats and in the North Sea, such gears have reduced the biomass and production of bottom-dwelling organisms. Sustained fishing has resulted in a shift from communities dominated by relatively sessile, emergent and high biomass species to communities dominated by infaunal, smaller bodied and faster growing organisms. Habitat impacts are related to the types of seabed communities and other sources of seabed disturbance such as wave and tidal action. The most sensitive species are emergent epifauna and slow growing reef building communities and the risk to these vulnerable habitats is likely to be reduced given that most of the footprint of the gear occurs on core fishing grounds.
Otter trawl fisheries can encounter moderate to high proportions of bycatch of other target and non-target species, although it is hoped this will be reduced through the ongoing implementation of the EU landing obligation. As dab itself is a commonly discarded bycatch species of other targeted fisheries (often for sole and plaice), this component has not been assessed in this rating. The gear type can also encounter bycatches of threatened shark, skate and ray species including the critically endangered common skate complex (Dipturus batis).
Some spatial management is in place but there remains a need to implement management measures in many designated marine protected areas to allow for the protection and recovery of these areas and sensitive designated features. There are MPAs designated to protect seabed features from damaging activities within the region that this assessment applies. The fishery overlaps with parts of these MPAs, but the proportion of the catch coming from these areas is expected to be relatively low in relation to the whole unit of assessment (i.e. less than 20% of the catch) and so these impacts have not been assessed within the scale of this rating. Given the important role that MPAs have in recovering the health and function of our seas, MCS encourages the supply chain to identify if their specific sources are being caught from within MPAs. If sources are suspected of coming from within designated and managed MPAs, MCS advises businesses to: establish if the fishing activity is operating legally inside a designated and managed MPA; and to request evidence from the fishery or managing authority to demonstrate that the activity is not damaging to protected features or a threat to the conservation objectives of the site[s].
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)
Sole, Dover sole, Common sole
Turbot (Caught at sea)
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Lakkeborg, S. 2005. Impacts of trawling and scallop dredging on benthic habitats and communities. FAO Fisheries Technical Paper. No. 472. Rome, FAO. 2005. 58p.
Tillin, H.M., Hiddink, J.G., Jennings, S. and Kaiser, M. J., 2006. Chronic bottom trawling alters the functional composition of benthic invertebrate communities on a sea-basin scale. Marine Ecology Progress Series. Vol. 318. 31-45.