Eastern Bering Sea

MUSSELS

Taxonomy: Phylum Mollusca, class Bivalvia, order Mytiloida, family Mytilidae

Species Representatives: Musculus discors, Modiolus modiolus, Mytilus trossulus, Musculus niger

Distribution and Life History: Mussels are members of the molluscan Class Bivalvia along with clams and scallops. The species listed here are widely distributed through the north Pacific and Atlantic (Austin, 1985). Attaching to the substrate and each other with byssal threads, mussels often form dense beds that support rich epifaunal and infaunal invertebrate assemblages. Other groups commonly associating with mussels are porifera (sponges), cnidarians (including hydroids, corals, and anemones), annelids, crustaceans, bivalves, bryozoans, and echinoderms (Brown and Seed, 1977). Mussel larvae remain in the water column for several weeks (O'Clair and O'Clair, 1998). Mussels are suspension feeders, filtering plankton and other small particles from the water column. Mussels are preyed upon by sea stars, gastropods and crabs (Harger, 1972).

Musculus discors (discordant mussel) - Small mussel (to 5 cm) often found in a cocoon of soft hairlike fibers (Kessler, 1985).

Modiolus modiolus (northern horsemussel) - Size to 15 cm (Kessler, 1985). General depth
range - intertidal zone to 200 m (Jasim and Brand, 1989). Both biomass and species diversity can be high within beds (Ojeda and Dearborn, 1989). In European studies they became sexually mature at 3-4 years; a fast growing population achieved a maximum shell length of 110 mm in 10 years; most populations included mussels in excess of 35 years in age, while the oldest individual was 48 years old and 133 mm in length (Anwar et al., 1990).

Mytilus trossulus (foolish mussel; previously: blue mussel) - Size to 13 cm (Kessler, 1985). Beds are composed of: 1) a physical matrix of interconnecting living and dead mussel shells, 2) a layer of accumulated organic and inorganic sediments and debris, 3) a taxonomically diverse assemblage of associated flora and fauna (Seed and Suchanek, 1992). Growth rates highly variable. In Puget Sound, grew to 50 mm length in 12-13 months (Skidmore and Chew, 1985). In a Maine population of the closely related Mytilus edulis, maximum age was 24 years (Steneck et al., 1978).

Musculus niger (black mussel) - Size to 8 cm (Kessler, 1985).