Several sites, surveyed by dredging, consist of a “scoured” substratum consisting largely of cobbles. All these sites were in channels or passes with high currents that affect the substratum well below 15 m.

Diagnostic Species

The horse mussel Modiolus modiolus, the giant barnacle Balanus nubilus, the serpulid worm Serpula vermicularis.

Common Associates

The urchins Strongylocentrotus pallidus and S. droebachiensis, the rock scallop Hinnites giganteus, the fan worms Sabellaria cementarium and Schizobranchus insignis, hydroids, ophiuroids, occasionally the basket star Gorgonocephalus eucnemis, anemones, and clam Humilaria kennerlyi.

Sites Surveyed

Haro Strait, Deception Pass, sites in the San Juan Islands.

Sources

Wennekens, 1959; R. Shimek, R. Anderson unpubl. data.