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Native Oyster

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Native Oyster

Description

Native oysters are highly prized but across their range they are becoming more and more rare. The stocks of native oyster in Falmouth and the Helford estuary are healthy and in Falmouth the Truro River Oyster fishery (whch produces Fal Oysters) is uniquely managed through a bylaw that has effectively frozen the fishery in time by banning the use of motors so that oyster are still collected using traditional sailing and rowing vessels. This makes Fal Oysters highly sustainable as well as a world famous delicacy.

Sustainability Overview

This low impact artisanal fishery is a great example of a the preservation of shellfish stocks through a simple ruling that has also preserved a traditional way of life and created a niche fishery product that has high marketing value. Fal oysters can only be caught under sail and oar, the dredges used are light weight and can only be pulled by hand.

The fishery is managed by Cornwall IFCA. Landings of native oysters  have decreased to a very low level in recent years as the traditional export market for native oysters for ongrowing in France has declined - sales were further harmed during the Covid lockdown and increased difficulties with exports since Brexit.  For this fishery to survive there is real need both to to improve marketing of the oysters to create a better UK market for them, and improving the management of this fishery further to ensure optimal sustainability. 

Updated July 2022

Sustainability ratings for this species

Sail and Oar

Truro river and Fal Estuary

Sustainably harvested using lightweight dredges that are towed by traditional sail boats and rowing boats. The unique management of this fishery has resulted in a sustainable harvesting regime that has kept stocks healthy for 150 years.

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How we rate fish

Cornwall Good Seafood Guide rates fish on sustainability using a scale of 1 to 5.

1, 2 and 3 are recommended, Fish to avoid are rated 5.

We use the system devised by the Marine Conservation Society (MCS) so our scores are comparable with the scores produced by MCS for the UK and fisheries from all around the world. For more information on scoring click here.

Biology

The native or flat oyster is a filter feeding, bivalve mollusc. They live on the seabed in relatively shallow coastal waters and estuaries (from the lower shore to 80m). They prefer habitats sheltered from strong wave action which tend to be muddy, but require something hard for larval settlement - usually shells or stones. All native oysters start out as males, and throughout their lives change back and forth from male to female. In Britain, breeding normally takes place in the summer. It reaches maturity at about 3 years old. The average reproductive size for the oyster is about 5cm. Oysters can reach a shell length of up to 11cm, and occur in variable shapes. Native oysters have a rough shell that is yellow, pale green or brown in colour, sometimes with bluish, pink or purple markings. The two halves of a native oysters shell are different shapes. The left shell is deeply concave and fixed to the substratum, the right being flat with rougher edges and sitting inside the left, acting as a lid. Inner surfaces of both valves or shells are smooth and usually pearly, white or bluish-grey, often with darker blue areas.The shell shape is a good way to distinguish native oysters from Pacific oysters, which were introduced to the UK in 1926, and which compete with the native oyster for space and food. Native oysters have rounder shells with smoother edges, while their Pacific relatives have a more elongated shell with deeply grooved edges. A single female oyster can produce 2 million eggs. Although usually up to about 11cm long, native oysters can grow to more than 20cm and can live as long as 20 years.
 

Stock Info

The harvesting of native oysters (O.edulis) and Pacific oysters in the the Fal Estuary for commercial purposes is an activity with more than two centuries history.  And it is the last remaining commercially viable native oyster fishery in the UK.
Despite the decline in the native oyster fisheries seen in the past for which Bonamia, pests, competition from slipper limpets chemical contaminants and TBT had contributed, the small fishery using sailing dredgers and hand dredging has been recovering in Carrick Roads (Walmsley and Pawson, 2007). 
Since 2014 the fishery has been managed by Cornwall Inshore Fisheries and Conservation Authority (CIFCA), they carry out annual surveys of the fishery.
Landings of native oysters declined in the winter of 2018 /2019 due to decreased demand for oysters from traditional French markets. large numbers of oysters (11,000 tonnes ) were placed on lays to grow on that season. There was an increase in landings of queen scallops which allowed the fishery to remain profitable. 
According to the detailed annual surveys carried out by Cornwall IFCA the stocks of oysters within the limited area of the Fal fishery fluctuate but remain within safe limits. A detailed stock assessment is not carried out but overall picture is of increased distribution and density of oysters on the beds and in recent years there has been a well documented increase in numbers of the scallop Mimachalmys varia (marketed as Queen scallops).

Management

The Truro River oyster fishery (producing Fal Oysters) is unique in its management, in that oysters can only be harvested using sail and oar power and dredges can only be hauled by hand. This is the only fishery of its kind and the overall effect has been to limit the fishery by making it more inefficient. In the recent article by Long et al (see references) this is argued to be the cause of the long-term success of this fishery in comparison to other less sustainable fisheries. The fishery has recently become the responsibility of Cornwall Inshore Fisheries and Conservation Authority. The 2016 Regulatory order for Fal Fishery modernised the regulation from the old fishery bye-laws and reduced the area which can be fished taking away the southern area of the fishery where the fishery overlapped with protected mearl beds and seagrass beds. Additionally an exclusion zone was also introduced around an area of seagrass found off Penarrow point. The minimum size of oysters which can be removed from the fishery are those which can hang on a ring of  67mm diameter can be harvested and oysters which pass through the ring must be put over the side of the boat back onto the fishery, or put onto oyster lays - areas on the very low shore set aside for oysters to be stored. There is a closed season for oyster fishing between 1st April and 30th September inclusive.  All dredges used must be licensed (Licence fee is currently £165 per year). Dredging can only be carried out between the hours of 9am and 3pm on weekdays and 9am and 1pm on a Saturday - there is no dredging allowed on a Sunday. The dredges themselves are limited to a maximum width of 1.2m, and the dredge must not have teeth, tines or other digging projections. The dredge must not exceed a weight of 20kg. These restrictions combined with the fact that only manual handling of dredges is allowed restricts the impact of the dredges on the seabed and makes this method of dredging far more sustainable than scallop dredging or oyster dredging under power. Cornwall IFCA fal fisheries Managment Plan 
 

Capture Info

Native oysters from the Truro river (Fal) oyster fishery are caught using low impact and heavily restricted methods. Lightweight dredges (without teeth) are pulled over the oyster beds slowly as only sail and oar power are permitted, the dredges have to be light enough that they can be hauled up by hand. Average length of tow of an oyster dredge is 6 minutes, this reduces impact and results in very little damage to accidentally by caught invertebrates and shellfish. the contents of the dredges are sorted on the side decks of the boat and after the marketable oysters are removed the shells and unwanted by-catch is returned immediatey un-harmed, over the side back, onto the fishery.  Un-marketable oysters which are too small to sell are often placed on lays – these are marked out sections of the intertidal within creeks on the fishery where oysters are allowed to grow before being harvested by hand by the fishermen at a later date.  The oyster beds have been fished in this way for centuries and the impact on the seabed is minimal. Oystermen say that dredging actually helps the oysters to grow by reducing sedimentation and removing excessive seaweeds and predators such as spiny starfish.  There is need for detailed research to investigate this claim frequently made by fishers.

References

 
Classification of bivalve mollusc Production areas in England and Wales, Sanitary Survey Report) Fal estuary(lower) and Percuil river 2012 CEFAS Kershaw and Campos
COUNCIL REGULATION (EC) No 510/2006 on protected geographical indications and protected designations of origin “Fal Oyster”  
 

Recipes for Native Oyster

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