Oyster, Native, oysters (Caught at sea)
Ostrea edulis
Method of production — Caught at sea
Capture method — Sail and oar
Capture area — North East Atlantic (FAO 27)
Stock area — Cornwall
Stock detail — 7e, 7f, 7g, 7h
Sustainability rating
info
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 80 m). 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 5 cm. Oysters can reach a shell length of up to 11 cm, 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 oyster’ s 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 11 cm long, native oysters can grow to more than 20 cm and can live as long as 20 years.
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.
Abalone
Clam, Manila (Farmed)
Crab, brown or edible
Cuttlefish
Limpet, Slipper
Lobster, European
Lobster, Norway, Langoustine, Dublin Bay prawn or scampi
Mussel, Chilean (Farmed)
Mussel, mussels (Farmed)
Oyster, Native, oysters (Caught at sea)
Oyster, Native, oysters (Farmed)
Oyster, Pacific, oysters (Caught at sea)
Oyster, Pacific, oysters (Farmed)
Prawn, King (whiteleg), prawns
Prawn, Northern prawns, Northern shrimp
Prawn, Tiger prawns (Farmed)
Scallop, King, scallops
Scallop, Queen, scallops
Squid, Japanese flying
This system has been developed by the Marine Conservation Society to help consumers choose the most environmentally sustainable fish. For
full details, please see the full wild-capture methodology available here.
Stock or species status
Score |
Descriptor |
0 |
Stock under fished and harvested within sustainable limits |
0.25 |
Stock fully fished and harvested within sustainable limits |
0.5 |
Stock level below sustainable level (BMSY) but harvested within sustainable limits |
0.75 |
Stock and fishing level or stock at increased risk |
1 |
Stock outside biological and/or safe fishing limits |
Management
Score |
Descriptor |
0 |
Well-managed |
0.25 |
Management requires some improvement |
0.5 |
Partly effective management |
0.75 |
Poorly managed and requires considerable improvement |
1 |
No relevant or effective management measures in place |
Capture method and ecological effects
Score |
Impact |
0 |
Very low impact |
0.25 |
Low impact |
0.5 |
Some or moderate impact |
0.75 |
High impact |
1 |
Very high impact or illegal |
Where environmental concerns from any one criteria are so great, a ‘critical fail’ may be triggered and the fishery awarded a default red
rating. For full details, please see the full wild-capture methodology available here.
The sustainability of fish can vary significantly depending on how and where it has been caught or farmed. Many single species are caught or farmed in a variety of ways and this range shows that, within a species, some sources may be more sustainable than others.
To find out specific ratings, click on the 'Show options for this fish' button under the image of the fish.
'Best choices' are rated 1 and 2 (green), 'Fish to Avoid' are rated 5 (red). Ratings 3 and 4 mean 'Think' (yellow and amber), as there are better rated alternatives.
Fish that are under review are shown with a question mark icon and no rating.
This system has been developed by the Marine Conservation Society to help consumers and businesses choose the most environmentally sustainable fish.
Seafood sources indicated as, 'To be assessed', are those that have not yet been assessed and assigned a rating or are undergoing a period
of review. These include sources previously rated by MCS for which the rating has lapsed, due to changes in the market or MCS priorities and
resources. Given that these sources are not fully assessed, the profile should not be used to infer the current sustainability of the
fishery or farmed species.
If you are interested in the sustainability of this seafood source, please let us know by emailing
ratings@mcsuk.org
Rating 1 (light green) is associated with the most
sustainably produced seafood.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 2 (pale green) is still a good choice, although some
aspects of its production or management could be improved
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 3 (yellow) based on available information; these
species should probably not be considered sustainable at
this time. Areas requiring improvement in the current
production may be significant. Eat only occasionally and
check www.goodfishguide.org for specific details.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
Rating 4 (orange) should not be considered sustainable, and
the fish is likely to have significant environmental issues
associated with its production. While it may be from a
deteriorating fishery, it may be one which has improved from
a 5 rating, and positive steps are being taken. However, MCS
would not usually recommend choosing this fish.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.
'Red improver' ratings are assigned to seafood sources which have been assessed and rated 5 (red) due to significant environmental concerns
with one or more aspects of their management, capture or production, yet credible efforts to improve these issues have been agreed through a
Fisheries or Aquaculture Improvement Project – a FIP or an AIP - and work is underway. Such projects are normally publicly listed at
www.fisheryprogress.org. MCS wants to encourage environmental improvements in fisheries and fish farms, and so does not recommend avoiding
these sources, as we normally do for seafood rated 5 (red rated).
'Best choice' fish are rated 1 and 2, Fish to Avoid are rated 5.
This system has been developed by the Marine Conservation Society to help businesses and consumers choose the most environmentally
sustainable fish.
Rating 5 (red) is associated with fish to be avoided on the
basis that all or most of the criteria for sustainablilty
have not been met.
Fish to Eat are rated 1 and 2, Fish to Avoid are rated 5.
Ratings 3 and 4 mean don’t eat too often.
This system has been developed by the Marine Conservation
Society to help consumers choose the most environmentally
sustainable fish.