Head to head
European Flat Oyster vs Blue Mussel
European Flat Oyster
VS Blue Mussel
The European flat oyster and the blue mussel are two bivalves that form dense beds on European shores, filtering the water and sheltering other animals.
| European Flat Oyster | Blue Mussel | |
|---|---|---|
| Scientific name | Ostrea edulis | Mytilus edulis |
| Relationship | A bivalve that filters food from the water | A bivalve that filters food from the water |
| Shell | A flat, rounded, rough shell, usually 6 to 11 cm across, with a deeper lower valve and a flatter lid | A smooth, wedge-shaped shell, blue-black outside and pearly inside, usually 5 to 10 cm long |
| Attachment | The lower valve is cemented to a hard surface | Attaches itself to rocks and to other mussels with tough threads called the byssus |
| Diet | Filter feeder, drawing in plankton and tiny particles from the water | Filter feeder, drawing in water and straining out microscopic algae and tiny particles |
| Breeding | Females keep fertilised eggs in the mantle cavity and release larvae after about ten days, and individuals can change sex | Releases its eggs and sperm into the water, where the larvae drift |
| Habitat | Sheltered coastal waters, estuaries, and shallow seabeds, once forming enormous reefs | Rocky shores and estuaries, forming thick beds that shelter many other small animals |
| Conservation status | Not Evaluated, but beds have declined drastically across Europe and restoration projects are under way | Not Evaluated, and farmed on ropes and poles in sheltered bays across the world |
European Flat Oyster vs Blue Mussel: common questions
Which one has declined most?
The European flat oyster, whose beds have declined drastically across Europe from overfishing, disease, pollution, and invasive species.
How does a mussel hold on?
It attaches itself to rocks and to other mussels with tough threads, called the byssus, which resist the pull of waves.
Why restore oyster reefs?
Reefs filter and clean the water and provide shelter and food for many other animals, so restoration helps whole ecosystems.