Bivalve Shellfish

mussels ... alive, alive oh!

Horse     Green-edged     Black-edged     Nesting and Ribbed mussels,     Scallop

Bivalve shellfish have two valves, or shells, hinged together along one side. Most bivalves feed by filtering plankton from the sea water.

Horse Mussel

(Atrina pectinata zelandica)

Habitat: Lives at or below low tide mark, usually in harbours or sheltered waters.

Identification: Has a thin and brittle shell which shines with iridescent colours. Grows to 33 cm, though normally not exceeding 18 cm.

General: The pointed end of the shell is normally buried deep in sandy mud with only 3 cm or so exposed. This is New Zealand's largest bivalve shellfish.


Green Edged Mussel

(Perna canaliculus)

Habitat: Attached to rocks and other objects, commonly at or below the low tide level.

Identification: Young shells are bright emerald green and darken with age. They grow to about 18 cm in length.

General: Our largest true mussel, this is the main species used for food in New Zealand. They attach to objects by fine threads called byssus (or beard).


Black Edged Mussel

(Xenostrobus pulex)

Habitat: Common around low tide level.

Identification: Smaller than the green edged mussel. The inside of the shell is marked with navy blue blotches.

General: Generally forms as a dense mass of mussels on a particular rock or object.


Nesting Mussel

(Modiolarca impacta)

Habitat: Lives at or below low-tide mark, attached to rocks and gravel.

Identification: The threads of the byssus form a nest inside which a whole colony of nesting mussels may live.

General: A relatively small mussel.


Ribbed Mussel

(Aulacomya ater maoriana)

Habitat: Lives in cracks and crevices on open, rocky coasts.

Identification: Shell has distinct ribs, setting it apart from the smoother shells of other mussels.

General: Seldom grows to an edible size.



Other Names: Common or fan scallop. (Pecten novaezelandiae)

Habitat: Generally found on sandy or silty bottoms, partially buried.

Identification: Has one flat and one concave valve and has a symmetrical shape. The curved shell is ridged or scalloped.

General: Scallops have two rows of iridescent eyes around the edge of the open shell and these can detect the approach of enemies. By opening and shutting its shells rapidly the scallop can swim in a jerky fashion and so often escapes danger.

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