The Mediterranean mussel is a smooth, blue-black mussel from the Mediterranean region and southern Europe that has become invasive in California and Puget Sound, clinging to rocks, docks, and boat hulls. In warm, salty water it crowds out the native bay mussel, and the two look so alike that only genetic tests can reliably tell them apart.
Appearance
- Appearance
- A smooth, teardrop-shaped shell, blue-violet to black, sometimes shading to light brown. It usually grows 2–3.5 in (5–9 cm) long, and big ones top 4 in (10 cm).
Look-alikes
Where it lives
- Typical habitats
- rocky shores
- docks and pilings
- harbors
- mussel farms
- Range
- Native to the Mediterranean and Black Seas and the Atlantic coast of southern Europe. In the U.S. it's established along the California coast and in Puget Sound, Washington, and it has turned up on ship hulls in Pearl Harbor, Hawaii.
- Preferred conditions
- Lives in the intertidal and shallow subtidal zones, anchored by tough threads to rock, wood, docks, and boat hulls.
Behavior
- Diet
- A filter feeder that strains plankton out of seawater.
Life cycle
- Reproduction
- Sexes are separate and spawning can stretch over much of the year. A female releases millions of eggs, and the larvae drift for 2–4 weeks before settling.
- Time to maturity
- Within about a year
Conservation
- IUCN Red List
- NENot EvaluatedNot yet assessed
- Status
- Listed among the world's 100 worst invasive species. In California it probably arrived on ships; it was first confirmed in 1987 using lab tests, though a rise in mussels in the 1940s may mark an earlier arrival.
- Threats
- Outgrows and crowds out the native bay mussel in warm, salty water, fouls ships and docks, and hybridizes with the bay mussel in central California, San Francisco Bay, and Puget Sound.
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