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Shrimp, brown or common

Crangon crangon

Method of production - Caught at sea
Capture method - Beam trawl
Capture area - North East Atlantic (FAO 27)
Stock area - VIIa
Stock detail - Solway Firth
Certification -
Fish type - Shellfish

Sustainability rating Click for explaination of rating

This fish, caught by the methods and in the area listed above, is not the most sustainable choice of fish to eat. Click on the rating icon above to read more and on the alternatives tab below to find more sustainable fish to eat.


Sustainability overview

Brown shrimp is a fast growing and resilient species and plays a very important role in the marine ecosystem. It is an important prey item for many species including seabirds and commercial fish such as cod and whiting, and is itself an important predator of smaller intertidal organisms. The fishery for brown shrimp in the Solway Firth primarily occurs in the Northwest Inshore Fisheries and Conservation Authority (NWIFCA) area and to a lesser extent in Scottish inshore waters and also deeper offshore waters. The fishery is relatively small, with 11 small shrimp beam trawlers regularly targeting the species. There is insufficient information available to inform a stock assessment and so the state of the stock is unknown, yet landings are considered stable. There are no catch and effort controls specifically for brown shrimp, but the strong tides and weather are believed to prevent the effort of the local fleet expanding. Despite this, there are no controls to prevent additional vessels entering the fishery. Whilst large reductions in bycatch have been achieved with the use of sieve nets, bycatch of small fish is still of concern in the fishery, particularly as the Solway is an important nursery area for various fish species including sole and plaice, both of which are overfished in the Irish Sea. It is thought that further reductions could be made with the use of square mesh panels or codends and through the increasing of the codend mesh size.

Beam trawling for brown shrimp in the region uses lighter gear than traditional beam trawls, yet the gear is still expected to impact on vulnerable habitats. Recent closures to protect the features of high risk European Marine Sites in this region are an important step forward, but more is needed to ensure all sensitive habitats are protected from damaging activities. Given the small size of the gear and fleet in this fishery, and the main areas where they operate (fast flowing sandy channels), and the recent closures, impacts to seafloor habitats are expected to be relatively moderate in this region.

Biology

Crangon crangon, the common or brown shrimp, is found in mainly shallow water along the Eastern Atlantic coast as far south as Morocco, and into the Mediterranean and Black Seas. It grows to about 8cm, with length at maturity between 35-50mm. Lifespan is 4-5 years, with females living longer. They mature within their first year of life. It has a relatively fast growth rate of 14mm per month during the first couple of months. Similar to lobsters and crabs, females carry their eggs on their abdominal appendages (the pleopods) for a period of 4-13 weeks, depending on temperature. Egg-bearing (berried) females can be found for 46 weeks of the year, but there are two peaks in numbers of berried females in the southern North Sea, and one in the Irish Sea. Peak reproductive periods occur between April and September, when females carry up to 4,500 small 'summer' eggs. The number of berried females decreases sharply in September, but then increases again in October/November as females produce up to 2,800 larger 'winter' eggs. Brown shrimp Crangon crangon is a major food item found in cod and whiting stomachs, and is itself an important predator of in- and epifauna in intertidal areas that is assumed to control plaice and mussel recruitment.

Stock information

Stock area
VIIa

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Stock information
Brown shrimp populations exhibit rapid growth, and also high natural mortality. There has been no stock assessment undertaken for brown shrimp in this region, and assessing such species is difficult as populations can widely fluctuate depending on environmental conditions and predation. Landings are monitored and whilst catch rate indicators suggest the stock is stable, these are not reported in relation to reference points, so the status of the stock is unknown. Application of the Marine Stewardship Council (MSC) Risk Based Framework methodology for the project Inshore project indicated that the fishery posed a medium or high risk to the productivity of the species, vindicating the need for stock assessment.

Management

The brown shrimp fishery in the Solway Firth in northeast England primarily falls under the managerial jurisdiction of the Northwestern Inshore Fisheries and Conservation Authority (NWIFCA) though some of the catch is taken within Scottish waters. The Project Inshore Phase II Report indicates that whilst fishery removals are monitored, there is little information available for the development of stock indicators and subsequent harvest control rules. The main fishery management measures applying to brown shrimp vessels in the region include:

- 13.72m vessel length limit between 0-3nm and 21.34m limit to bay closing lines in the Solway (Most if not all boats accessing the fishery are between 7 and 13.72m in length);
- A maximum aggregate beam length of 9m,
- Use of a separator grid or sieve net for all shrimp trawls with an aggregate beam/headline length of over 8m (except where catches of shrimp are 5% or less of the total catch);
- The requirement to empty catches onto a grader with no less spacing than 5mm by 60mm where any marine life passing through the grid is returned to the sea.

- There are no catch limits in place, yet the development of TACs based on an annual stock assessment for brown shrimp is problematic due to the short life span of the species. However, a real-time harvest control rule based on catch rates has been recommended as a suitable precautionary management tool in the North Sea and could also be considered for the Solway.
- There are no effort limitations, but is believed that the strong tides and weather essentially limit the effort of the existing fleet.
- There are no limits to mesh size, but the IFCA is currently consulting on this. Research undertaken by Lancaster (1999 ) indicated that juvenile catches of shrimp and fish could be reduced by increasing the mesh size to an optimum 25mm (as opposed to the 21mm in use) and by the use of square mesh panels or codends.
- Lancaster (1999) also investigated the option of closures to protect shrimp nursery areas, yet concluded that these would not be necessary, as the shrimp nursery areas are among the intertidal flats which are not accessed by the trawl fishery.

A number of spatial closures are in effect. Most recently, the NWIFCA has implemented six area closures to protect the features (such as reef and seagrass) of European Marine Sites from high risk activities such as bottom trawling within its jurisdiction.

Capture information

The Solway Firth brown shrimp fishery is very old and has reportedly been active for over 100 years. Shrimps are caught year round by beam trawls operating in low-water channels with peaks in Autumn and Spring. In Winter, shrimps move further offshore where they my be caught by larger vessels. The small fishery currently has 11 small shrimp beam trawl vessels; nine from the Cumbrian fleet and two from the Scottish fleet. Occasionally vessels from elsewhere fish these waters as well. Vessels vary in length between seven and 13.3m. Six vessels reportedly use twin beams, approximately 4.5m each side, with the others using single beams up to 9m in length. When targeting shrimp, a very small mesh size (approx 20mm) is used in order to retain the species and so larger species are often caught as bycatch.

The Solway Firth (like most brown shrimp grounds) is an important flatfish nursery ground, and so to reduce this bycatch vessels need to use both veil nets and riddles. Veil nets are larger mesh panels that are stretched across the mouth of the codend to exclude larger animals (>10cm) from entering the codend. A riddle separates consumable size shrimps (usually >45 mm total length) from non-commercial by-catch (a wide variety of benthic species mostly crustaceans, echinoderms and molluscs, fish and undersized shrimp) which is discarded into the sea. The catch is generally cooked on board the vessel. Survival rate of brown shrimp seems to be high in the entire capture, hauling, riddling, discarding and bird predation processes. A three year study investigating post capture survival of undersize shrimp in the fishery found that 75-80% survival is estimated. However the survival of juvenile flatfish is less likely. Approximately 19% of the catch (by weight) is made up of mainly juvenile plaice, dab and whiting , pogge and weevers. In 1987, a study suggested that in the Irish Sea, the yield of sole and plaice was estimated to reduce 1.4 and 8.9% respectively as a consequence of the English West coast brown shrimp fleet activities, however other studies have suggested the impact may be smaller given the very high natural mortality of these juvenile fish. As both sole and plaice in the Irish Sea are currently overfished, further efforts should be made to reduce all incidental mortality of these species from shrimp fisheries. Research undertaken by Lancaster (1999 ) indicated that juvenile catches of shrimp and fish could be further reduced by increasing the mesh size to an optimum 25mm (as opposed to the 21mm in use) and by the use of square mesh panels or codends.

The Solway Firth forms one of the largest continuous areas of intertidal habitat in Great Britain and has long been recognised as having great environmental importance. Areas of the Solway Firth are designated both as a Special Area of Conservation (SAC) under the Habitats Directive and a Special Protection Area(SPA) under the Birds Directive - collectively known as the Solway Firth European Marine Site(EMS). Beam trawling is associated with damage to sea floor communities, particularly upright invertebrates and other reef building organisms. However, the impact on such communities is often dependent on the natural disturbance regime of the area. As the Solway is highly tidal and made up of shifting sand backs, damage to seafloor communities may be comparatively minor, particularly given the small size of the vessels and relatively small scale of this fishery. The NWIFCA has recently implemented six area closures to protect the features (such as reef and seagrass) of European Marine Sites from high risk activities such as bottom trawling. There remain several other medium risk sites which need to be evaluated to assess if certain activities like trawling should be allowed.

Read more about capture methods


References
Food Certification International, 2013. Project Inshore Report, Stage 2 V4 draft. Prepared for Seafish. Available at http://www.seafish.org.uk/media/921067/2013.07.23_project_inshore_s2_v5.pdf [Accessed July 2015].

Lancaster, J. 1999. Ecological studies on the brown shrimp (Crangon crangon) fishery in the Solway Firth. PhD Thesis, University of Newcastle Upon Tyne, United Kingdom.

Lancaster, J. & Frid, C.L.J. 2002. The fate of discarded juvenile brown shrimps (Crangon crangon) in the Solway Firth UK fishery. Fisheries Research 58, 95-107.

Nautilus Consultants, 2013. The Future of Sea Fisheries in Dumfries and Galloway: Final Report. Prepared for Dumfries & Galloway Council. Available at http://www.solwayfirthpartnership.co.uk/uploads/fish/Dumfries%20and%20Galloway%20report%20Final.pdf [Accessed July 2015].

NWIFCA Byelaws, June 2014. Available at http://www.nw-ifca.gov.uk/contents/images/Byelaws%20and%20application%20forms/NW%20IFCA%20byelaws%20incl%20Dee%20(June%2014).pdf [Accessed July 2015].

NWIFCA, 2015. Personal communication. 30 July, 2015.

Palomares, M.L.D. and D. Pauly. Editors. 2015. SeaLifeBase. World Wide Web electronic publication. Available at www.sealifebase.org {Accessed July 2015].

Sankey, S.A. 1987. The shrimp fishery and its by-catch in north western and North Wales fisheries district. North Western and North Wales Sea Fisheries Committee, Lancaster, UK.

Sewell, J. & Hiscock, K., 2005. Effects of fishing within UK European Marine Sites: guidance for nature conservation agencies. Report to the Countryside Council for Wales, English Nature and Scottish Natural Heritage from the Marine Biological Association. Plymouth: Marine Biological association. CCW Contract FC 73-03-214A. 195 pp. Available at http://www.marlin.ac.uk/PDF/FishGuidance05_Final_Report_screen.pdf [Accessed July 2015].

Solway Shellfish Management Association, 2004. Solway Firth Regulating Order DRAFT Management Plan. Available at http://www.snh.org.uk/pdfs/scottish/dumfries/MgtPlan.pdf [Accessed Jul 2015]

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