Many factors determine the distribution, species composition, and abundance of the invertebrate fauna. The seafloor geology, types of rocky substrate or unconsolidated sediments, offshore currents and circulation patterns, exposure to waves, water depth, Columbia River low salinity plume, and presence of mammal predators all influence the niches occupied by the various species. The upwelling off the coast brings cold, nutrient-rich water to the nearshore zone where it nourishes high marine plant productivity. This provides food and habitat for invertebrates that suspension feed or graze on algae (Dethier, 1988).

The rocky intertidal habitat supports the widest array of invertebrate species (Ricketts et al., 1985). Representative invertebrates include sponges, bivalves, isopods, amphipods, shrimp, barnacles, bryozoans, sea urchins, sea cucumbers, and sea stars.

Invertebrates residing in the boulder and cobble areas are diverse and consist of organisms living on and around the rocks and the soft sediment beneath them. Different species dominate in this habitat than in the rocky intertidal areas. Invertebrates living in the sediment under the rocks include the mud shrimp (Upogebia), mud dwelling brittle stars, and several species of clams and polychaete worms. Invertebrates living on or under boulders and cobbles include barnacles, limpets, amphipods, isopods, sea snails (Lacuna and Tegula), several species of crabs, the sea squirt Clavelina, and various species of edible clams (butter clams, littleneck clams, and horse clams).

Invertebrates found in sandy intertidal areas are less diverse than in other habitats, but some species may be found in large numbers. For example, Dethier (1988) discovered great quantities of amphipod crustaceans and polychaete and nemertean worms at several sites on the outer coast. The amphipod Euhaustorius was found in densities up to 10,670 individuals/m2. Densities of the bloodworm Euzonus reached almost 7,000/m2. Other invertebrates present include razor clams (Siliqua), isopods, mysids (opossum shrimp), sand dollars, purple olive snails, several species of clam (e.g. Macoma secta and Tellina bodegensis), and Dungeness and mole crabs.

Invertebrates associated with kelp beds include many encrusting varieties such as sponges, bryozoans, and tunicates. Other invertebrates include amphipods, copepods, euphausiids, numerous species of crabs, sea urchins, shrimps, sea stars, brittle stars, periwinkles, limpets, sea snails, sea slugs, scallops, and abalone.

Squid, octopi, jellyfish, salps, heteropods, shrimp, and euphausiids are some of the macro-invertebrates found in the pelagic environment. Numerous larval invertebrates are also found there during their planktonic stages of development.

Thus, both the coastal and offshore areas are important to invertebrates depending on whether the invertebrates are sedentary or pelagic. Four invertebrates are particularly significant within the study area: 1) Pacific oyster, 2) ocean pink shrimp, 3) Dungeness crab, and 4) razor clam.

Pacific oyster, Dungeness crab, and ocean pink shrimp landings from the areas under consideration for sanctuary status had combined landed values in 1987-88 of over $25 million (about 85% of the statewide totals for harvests off Washington) (WDF, 1987; NMFS, 1989).

Decimation of razor clam populations due to pathogen infestations and other natural calamities in the early 1980's has ended commercial harvests, but recreational digging on Washington's outer coast currently accounts for over 70% of the contiguous US coastal sport harvest.

Oyster production is particularly significant in Grays Harbor and especially Willapa Bay. These two estuaries account for over half of all oysters harvested along the entire US West Coast, and sometimes represent nearly 1/5 of the nationwide harvests (NMFS, 1989a).

Invertebrates Species List