Tidepool with an assortment of invertebrates.
Many factors determine the distribution, species composition, and abundance of the invertebrate
fauna. 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.
Anemones, ochre sea stars, and three types of barnacles share this niche.
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. The rocky intertidal habitat supports a diverse array of invertebrate species. Representative
invertebrates include sponges, bivalves, isopods, amphipods, shrimp, barnacles, bryozoans, sea
urchins, sea cucumbers, and sea stars.
Large rocks and boulders provide habitat for many invertebrates.
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
), several species of crabs, the sea squirt
, and various species of edible clams (butter clams, littleneck clams, and horse clams).
Razor clams can often be seen on or in the sand.
Invertebrates found in sandy intertidal areas are less diverse than in other habitats, but some
species may be found in large numbers. Researchers have observed great quantities of amphipod
crustaceans and polychaete and nemertean worms at several sites on the outer coast. The amphipod
was found in densities up to 10,670 individuals per square meter. Densities of the
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.
and Tellina bodegensis
), and Dungeness and mole crabs.
A moon snail nestles in a variety of kelp.
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.
Octopus and brittle star curl their arms.
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 percent of
the statewide totals for harvests off Washington) according to records of the Washington Department
of Fish and Wildlife.
Decimation of razor clam populations due to pathogen infestations and other natural calamities in
the early 1980s has ended commercial harvests, but recreational digging on Washington's outer coast
currently accounts for over 70 percent of the contiguous US coastal sport harvest.
Visitors come from across Washington state to dig clams along the coast.
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 one-fifth of the nationwide harvests according to the National Marine
Contact for page content: Jacqueline Laverdure