Although they may resemble the rocks they're found on, mussels are very much alive. These filter-feeders can form large dense beds that account for significant biomass within the rocky intertidal and provide an important food source for many other species, including ochre sea stars, snails, and humans. Mussels are considered foundation species--a single species that creates locally stable conditions for other species--and are among several keystone and foundation species that are critical to maintaining OCNMS’s ecosystem structure, function, and stability over time.

Map of Sites

An interactive map of Multi-Agency Rocky Intertidal Network (MARINe) sites within Olympic Coast National Marine Sanctuary (purple shading).

Interactive Trends - Mussels

Average abundance of California mussels Mytilus californianus measured as percent cover in rocky intertidal monitoring plots at six locations adjacent to OCNMS since 2007. The bold, black line indicates the sanctuary-wide annual abundance calculated by averaging across the six sites. Only data from permanent plots focused on mussels were used. Source: Multi-Agency Rocky Intertidal Network (MARINe)

Trends - Mussel condition

Pfister et al, 2016

A comparison of California mussel relative shell thickness for modern (2009–2011), archival (1970s), and midden (radiocarbon dated 1000–1340) samples at two sites in Washington state: Tatoosh Island (a–c) and Sand Point (d–f); (a, d) total thickness, (b, e) thickness per shell length, and (c, f) thickness per year of age. Image: Pfister et al., 2016.