Pacific oyster

Magallana gigas

Pacific oyster

Image | Seafish

Description

Oysters are delicious and good for you with a distinctive taste of the sea. Pacific oysters are a non-native species that has been introduced to the UK for aquaculture.  It is much more commonly found offered for sale than the native or flat oyster. Pacific oysters are more slipper-shaped than their flat native cousins, and the edges of the shell have distinctive wavy large frills.In some areas this species has escaped captivity and has become an invasive species.


Sustainability Overview

Pacific oysters have been farmed on the banks of the Camel estuary since the 1960's. They are cultured in plastic sacks which are turned by hand each tide. The culture of oysters is low impact and doesn’t add pollution to the water. The only disadvantage is the risk of oyster larvae (spat) escaping and colonising nearby natural habitats. This hasn't happened in the Camel estuary possibly due to the sandy nature of the environment in this area preventing the settlement of spat. In some areas of the UK native oysters are now totally wild and they significantly alter the nature of seabeds creating oyster reefs which displace other species but provide habitat for a different set of species, there is increasing evidence that this is happening in south coast cornish estuaries with potential to massively alter intertidal habitats. 

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When is best to eat?

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Farmed

Farmed on the shore in semi rigid plastic mesh cages.

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How we rate fish

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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.

Sustainability Overview

Pacific oysters have been farmed on the banks of the Camel estuary since the 1960's. They are cultured in plastic sacks which are turned by hand each tide. The culture of oysters is low impact and doesn’t add pollution to the water. The only disadvantage is the risk of oyster larvae (spat) escaping and colonising nearby natural habitats. This hasn't happened in the Camel estuary possibly due to the sandy nature of the environment in this area preventing the settlement of spat. In some areas of the UK native oysters are now totally wild and they significantly alter the nature of seabeds creating oyster reefs which displace other species but provide habitat for a different set of species, there is increasing evidence that this is happening in south coast cornish estuaries with potential to massively alter intertidal habitats. 

Pacific oyster

Biology

Oysters belong to the commercially important group of bivalve molluscs which also includes mussels, clams and cockles. The Pacific oyster, now widely distributed, originated in northeastern Asia. Pacific oysters, as with many oyster species, develop first as males, spawn, and then later develop into females. Spawning occurs in the summer.  

Stock Info

There are no wild capture fisheries for pacific oysters in Cornish waters. Oysters are bred in hatcheries and then grown on in the sea - usually in semi-rigid plastic mesh bags, supported by steel trestles secured in intertidal waters. Pacific oyster producers rely on spat from oyster hatcheries which have been manipulated (making them triploid - having three sets of dna) which ensures that they should not spawn in the wild although some escapees have been found in recent years in Cornish estuaries, where they appear to now have self sustaining populations. To prevent this DEFRA requires oyster farmers to use sterile triploid oyster spat. 

Management

Marine aquaculture is regulated by DEFRA and environmental health. Although they spawn in summer farmed oysters are available all year round as after harvesting they are carefully depurated to remove impurities and toxic algae. 

Capture Info

Farmed on the shore often on steel tressels in semi rigid plastic mesh cages. 

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