In an effort to honor the tastiest Pacific Northwest invertebrate, I'll begin this entry with the crab.
Dungeness Crab: This crab has a purple tinged back with a cream-colored underside. Mature Dungeness crabs are typically 6-7” across. Dungeness have several pairs of appendages. Two pairs (antennae) are for touch and smell. A number of modified appendages act as a mouth, used for cutting, picking, sorting and pulverizing food. The pincers appendages are used for grasping, tearing and defense. Each crab has four pairs of walking legs. A sideways walker, a crab will push with four legs on one side and pull with the other side. Appendages are also located on an up-tucked tail; the female uses these appendages to hold onto her eggs. Crab are able to regenerate lost appendages.
Mating occurs between hard-shelled males and recently molted, soft-shelled females, generally in the late spring and summer. Male crabs are polygamous. Females store the fertilized eggs for several months under their abdomen until the eggs hatch (between February and April). Large females can carry more than 2.5 million eggs. For the first 90-120 days after hatching, Dungeness crabs are free-floating planktonic larvae. Larvae settle down onto the bottom of an estuary or nearshore environment between June and September, where they molt into recognizable crabs. Crabs can molt as many as ten times in their first year.
Dungeness are both predators and prey throughout their lives. They feed on fish, shrimp, and clams and are a food source for fish (e.g. halibut, dogfish, hake, lingcod) and octopus. Crabs will also eat other crabs.
A hard shell is necessary to protect the crab and to function as a skeleton, but once a shell hardens, the crab cannot grow any larger. Growth can only occur with shedding of the shell (molting). The crab will first begin to grow a soft shell and then backs out of its hard shell through a crack. Shedding the hard shell takes about 15 minutes, but it takes approximately two months for the newly developed soft shell to harden. During this period, crab are vulnerable to predators and tend to hide in the sand or mud. The crab’s newly formed shell is usually 11-29% bigger than the previous shell. A mature crab molts about once a year.
Pacific Oyster: The Pacific oyster is a non-native species. It was introduced into our waters from Japan- hence one of its common names- Japanese oyster. The Pacific oyster is a bivalve (composed of 2 shells hinged together). The average size of a 2-3 year old oyster is 4-5 inches, however it has been known to reach lengths up to 10 inches. The Pacific oyster prefers to attach itself to a hard surface and can be found on firm mud, sand, gravel or rock substrate in the lower inter-tidal zone, down to a depth of roughly 13 feet. The range of the Pacific oyster on the west coast of the United States extends from southeastern Alaska down to southern California.
All shellfish are filter feeders, filtering many times their weight in water. They feed on plankton and detritus. Problems arise when pollutants, from bacteria to heavy metals, are present in our marine waters. The oyster filters the water and accumulates the pollutants in its tissues. This can result in illness and sometimes death in humans who consume the oyster.
Pacific Littleneck Clam and Manila Clam: Collectively called "littlenecks" or "steamers", the native Pacific littleneck clam and introduced manila clam, or Japanese littleneck, both have circular rings and radiating ridges that criss-cross on the shell. Reaching 3", these hard-shell clams are buff to gray outside, sometimes mottled with color patterns resembling southwest pottery. Manilas have an oblong shape with some purple coloration on the inside of the shell. The native littlenecks have a rounder shape with chalky-white inside the shell. Pacific littlenecks range from Baja California to Alaska's Aleutian Islands, primarily abundant in estuaries north of Oregon.
Both are found buried at depths of 1-6 inches in mixed substrates of gravel, sand and mud. Generally, native littlenecks are concentrated in the mid-intertidal reaches while manilas thrive above the mid-tide level. Triggered by the warming waters of spring, the sedentary adult clams release spawn into the water column from April to September. Once the eggs are fertilized, embryos develop into larvae that drift with water currents and feed on phytoplankton. After 2 years the clams are about one inch in diameter and sexually mature. These clams require over 3 years of growth to reach 1½ '', the legal harvest size. As the estuary tides flood their burrows, the sedentary clams extend their necks to siphon passing water, filter-feeding on plankton and suspended detritus (bits of decaying organic matter). Predators of the littlenecks - crabs, octopi, snails, diving ducks - meet the challenge of finding the clams, digging them from the gravely mud and breaking or grinding through the shell. Often, gulls can be seen dropping and breaking clams on rocks or other hard surfaces. An estimated seven million pounds of clams are produced commercially in Washington State annually, the majority being farmed manila clams. A creation story tells of how Raven first discovered humans in a clam and set them free.
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