The mussel is found in the rocky intertidal zone.
Mussels are filter feeders and they eat the plankton, helping to make the water clearer.
This in turn allows more light penetration and photosynthetic processes to take place. Mussels are competitors in that they aggregate in clumps and leave little space for other organisms to occupy. As far a predators are concerned, Starfish particularly prey on mussels and do so by exerting force great enough to pull the valves apart. Other predators include crabs, gulls, sharks, rays, fishes, and flesh-eating snails. The bivalve shell contains two valves.