Mediterranean Mussels

Mediterranean mussels look similar to blue mussels but have a few small differences in physical appearance. They tend to grow larger than blue mussels and their mantle edge is darker, becoming blue or purple. They are also known as the black mussel because their shell can be dark blue, brown, or an almost black color. Their two valves are equal in size, each rounded with a slightly bent edge. They can grow an average between 2-3 in (5-8 cm) but can grow up to 6 in (15 cm). Intertidal mussels are usually smaller, rarely exceeding 2.4 in (6 cm), while deep-water mussels can easily grow up to 3.5 in (9 cm).

Mediterranean mussels grow quickly, capable of reaching nearly 3 in (7 cm) within the first year of growth in favorable conditions. They have high fecundity, capable of reproducing multiple times per year and reaching sexual maturity at 1-2 years. They reproduce via broadcast spawning, releasing their gametes into the water column. Fertilized eggs will develop into free-swimming larvae, which will then attach to rocks. In California, spawning and recruitment occurs year-round, with the heaviest being from February-April and again from September-October.

Mediterranean mussels are ecologically important in coastal ecosystems and are considered “ecosystem engineers,” as their beds provide shoreline protection and important habitat and shelter for many species. They are suspension feeders, feeding on detritus and phytoplankton like green algae, dinoflagellates, and diatoms through their gills. As filter feeders, they help remove pollutants from the water. Mediterranean mussels are also an important food source for other species, like sea stars and birds such as seagulls.