SHRIMP, CRAB, CLAM & OYSTER - Some of our Favorite Seafoods

Click For Image	Life-History Profile	Scientific Name
	Bay Shrimp	Cramgon franciscorum
	Dungeness Crab	Cancer magister
	Pacific Littleneck Clam	Protothaca staminea
	Pacific Oyster	Crassostrea gigas

BAY SHRIMP Cramgon franciscorum

Illustration courtesy of NOAA.

BAY SHRIMP

DID YOU KNOW? The bay shrimp is the most common shrimp in most Pacific coast estuaries.

SCIENTIFIC NAME: Crangon franciscorum.

COMMON NAMES: Sand shrimp, grass shrimp, common shrimp, black shrimp, California shrimp, and black tailed shrimp.

DESCRIPTION: Stout, depressed body with a thin shell and smooth surface. Color tends to be a dark and light yellowish gray with salmon-colored eyes.

LIFECYCLE: The bay shrimp is sensitive to temperature and salinity changes during its lifecycle. During reproductive periods which vary greatly with geographical location, bay shrimp move toward more saline areas of the estuaries to spawn. In their early life-stages, juveniles utilize the upper parts of estuaries as nurseries, preferring the lower salinity there. As it grows and matures, the bay shrimp moves to more saline areas of the estuary and offshore. Water temperature is especially critical to the bay shrimp as a regulator of its life functions. Females usually produce 2,000 to 8,000 eggs, and store the male's sperm inside their bodies. Egg fertilization is done when the female extrudes eggs into her 'brood pouch'; she carries with her for approximately 8 to 12 weeks until they hatch. Maturity is commonly reached in 1 to 1.5 years.

RANGE: Common in most Pacific coast estuaries from San Francisco to Puget Sound, although the bay shrimp is also found south of San Francisco to San Diego. The bay shrimp is abundant in bays with mud and sandy bottoms and offshore in deeper waters.

HABITAT AND ECOLOGY: As the most dominant shrimp in Pacific coast estuaries, the bay shrimp is an important part of the food chain. It is the predominant food of many sport and recreational fish, including striped bass, sturgeon, Dungeness crab and Pacific tom cod. The bay shrimp itself commonly feeds on bottom dwelling animals (epibenthic fauna), amphipods and plant material. In search of food, bay shrimp agitate the bottom and cycle nutrients into coastal systems. It is a short lived species that is sensitive to pollution in estuaries. Males commonly only live until their first spawn, 1 to 1.5 years, while females can live until their second spawn, approximately 2 to 2.5 years.

Because of the bay shrimp's preference for different levels of salinity during its lifecycle, freshwater inflow into estuaries strongly influences distribution, survival, and abundance. Maintaining the flow of freshwater into estuaries is critical because of its impact on water temperature, salinity, and landward currents. Because estuaries play a critical role in the bay shrimp's life history, alteration of this habitat directly affects its populations.

ECONOMIC VALUE: Fished commercially since the 1800's, the bay shrimp is presently fished commercially only in San Francisco Bay with landings ranging from 2 - 25 tons per year. It is fished mainly for bait. Some is used for human consumption though shelling and marketing bay shrimp is not economically lucrative.

DUNGENESS CRAB Cancer magister

Illustration courtesy of NOAA.

DUNGENESS CRAB

DID YOU KNOW? Male dungeness crab find females with the use of pheromones (chemical scents) and after mating the male may remain with the soft-shelled female for two days to insure her protection.

SCIENTIFIC NAME: Cancer magister, cancer is Latin for crab.

COMMON NAMES: Pacific edible crab, dungeness crab, market crab, commercial crab, and edible crab.

DESCRIPTION: Beige to light brown with blue trim; often light orange below. Short eyestalks with small orbits. Broadly oval carapace; uneven, but not highly sculptured.

LIFECYCLE: Mating occurs outside of estuaries in near-shore coastal locations. Eggs hatch in two to three months. Larvae are planktonic using tidal currents to self propel and "hitch-hike" on jellyfish in order to travel into estuaries. Juveniles settle in shallow coastal waters, tidal flats, and estuaries, living on beds of eelgrass and other aquatic vegetation. Growing through a series of molts to adulthood, the Dungeness crab is common in coastal waters offshore and in estuaries. Studies suggest that growth rates vary along the Pacific coast and that higher water temperatures in estuaries (> 6 degrees Celsius) and abundant food can accelerate growth.

HABITAT AND ECOLOGY: The Dungeness crab plays an important role in the food chain as predator and prey in estuarine and marine environments. Early in life, Dungeness crab fall prey to nemerteans (marine worms) that feed on their eggs. Dungeness crab larvae are important food for Pacific herring, Pacific sardines, rockfish, and chinook salmon. Juvenile Dungeness crabs are eaten by starry flounder, English, and rock sole, lingcod, rockfish, sturgeon, sharks, and skates. As juveniles living in estuaries, Dungeness crab feed primarily on fish, shrimp, molluscs, and crustaceans. During this life-stage, estuaries are especially important; thus any action, such as dredging or habitat modification projects, should be considered in light of their impacts on Dungeness crab. Adults feed on shrimp and bivalves and are eaten by humans, harbor seals, and sea lions.

Dungeness crab are intolerant of low dissolved oxygen conditions, and even low concentrations of ammonia are toxic. The insecticide sevin (carbaryl) which is sometimes used to control ghost shrimp in Pacific oyster beds is also very toxic to Dungeness crab. Dungeness crab larvae are highly sensitive to other insecticides and fungicides as well. They are also impacted by urban pollutants such as heavy metals, PCBs, and hydrocarbons. Concentrations of these contaminants presently exist in San Francisco Bay and sublethal impacts have been observed. The control of non-point source pollution -- pollution resulting from the runoff of pesticides and herbicides from our yards and farmland, as well as heavy metals and hydrocarbons from our streets -- is important to the health of Dungeness crab populations.

RANGE: Found in coastal waters from Santa Barbara, California, to the Pribilof Islands, Alaska. Dungeness crab probably inhabit all estuaries from Morro Bay, California to Puget Sound, Washington. Two important juvenile crab production estuaries are Willapa Bay and Grays Harbor in Washington state.

ECONOMIC VALUE: An important commercial shellfish harvested along the coast from California to Alaska, Dungeness crab are usually caught in nearshore marine waters under 120 feet deep with baited crab pots. An average of 17,000 tons, worth tens of millions of dollars, are caught annually, usually in the first two months of an average nine month season. Recreationally, Dungeness crab are also important, and are caught intertidally by hand or subtidally by crabpots, nets, or even hook-and-line.

PACIFIC LITTLENECK CLAM Protothaca staminea

Illustration courtesy of NOAA.

PACIFIC LITTLENECK CLAM

DID YOU KNOW? A small juvenile clam can use its foot to crawl to new areas.

SCIENTIFIC NAME: Protothaca staminea.

COMMON NAMES: Tomales Bay cockle, common littleneck, rock cockle, hardshell, rock clam, steamer and butter clams.

DESCRIPTION: Suboval shell with radiating ribs and concentric ridges. The color is highly variable. In the ocean and along the coast, the color is often whitish with patterns of brown lines along the sides. In bays and estuaries, the color is commonly gray or yellowish gray. Pacific littleneck clams are commonly found in the first 2 to 3 inches of substrate, and are found up to 2.5 inches in length.

LIFECYCLE: Spawning in the spring or summer depending on the region, pacific littleneck clam eggs and larvae are dispersed by the current throughout the water column. After developing a foot, larvae move to the bottom and search for a suitable surface to which they can attach. Young clams often attach in deeper water. As the clam grows, it moves toward shallower water. Adults are sedentary.

HABITAT AND ECOLOGY: Adult and juvenile Pacific littleneck clams are found in coarse, sandy-rock muds of estuaries and on the open coast where there is appropriate substrate, detritus (decaying plant material) and protection from predators. This species gathers food by filtering water for phytoplankton and diatoms. Rock crabs, fish, birds, sea otters, and others feed on clams depending on the region.

Because of their sedentary nature, clams are highly susceptible to human-induced changes in their environment. High coliform bacteria levels resulting from municipal sewage discharges have permanently closed some areas to harvest. High siltation caused by logging, upland development, dredging, and marina construction affect the abundance of Pacific littleneck clams. In addition, this species of clam is very sensitive to copper which is used in antifouling boat paint. Coastal wetland destruction also adversely impacts this species since detritus, generated by the decay of wetland plants, is an important food source for the clam.

RANGE: The Pacific littleneck clam is abundant in Pacific coast estuaries from Baja California to the Aleutian Islands in Alaska. Significant spawning grounds include Coos Bay, Tillamook Bay, Yaquina Bay, and Puget Sound, Grays Harbor and Willapa Bay.

ECONOMIC VALUE: An important part of the heritage of many coastal communities and a key factor in rural economies, the Pacific littleneck clam is commercially harvested from Prince William Sound, Alaska, to Southern California. Pacific littleneck clams make up 8% of the entire clam harvest along the Pacific coast and is usually sold fresh in the shell, frozen or canned. Additionally, the Pacific littleneck clam is an important recreational species due to its good taste and accessible habitat.

PACIFIC OYSTER Crassostrea gigas

Illustration courtesy of NOAA.

PACIFIC OYSTER

DID YOU KNOW? Pacific oysters were introduced from Japan. They develop first as males, and after a year begin to function as females.

SCIENTIFIC NAME: Crassostrea gigas.

COMMON NAMES: Japanese Oyster, Miyagi oyster, giant oyster, immigrant oyster, and giant Pacific oyster.

DESCRIPTION: Rough shell that is highly fluted and laminated. Shells are usually whitish with purple streaks and spots. Can reach 10 inches in length.

LIFECYCLE: The Pacific oyster is an exotic species, introduced into west coast estuaries from Japan. Because spawning depends on a rise in water temperatures above eighteen degrees Celsius, it only spawns erratically in west coast estuaries. As a result, cultured "spat" is used to seed oyster beds. When spawning does occur, it occurs primarily in July and August. Eggs and larvae are planktonic distributed throughout the water column in estuarine waters. Later stage larvae settle out of the water column and crawl on the bottom searching for suitable habitat before settling. Juveniles and adults are sedentary and are found in lower inter-tidal areas of estuaries. Oysters prefer firm bottoms, and usually attach to rocks, debris or other oyster shells. However, they can also be found on mud or mud-sand bottoms.

RANGE: In North America, the Pacific oyster is found from Southeast Alaska to Baja California. It is cultivated primarily on oyster farms in protected coastal estuaries; however, some wild beds exist in Washington and British Columbia.

HABITAT AND ECOLOGY: The Pacific oyster is a highly valuable estuarine species which is threatened by pollution in its environment because it concentrates contaminants. Presently, many estuarine areas are completely closed to oyster culture and harvest because of bacterial and chemical contamination associated with urban centers, marinas, and sewage outfalls. In fact, on any given day in the United States, one third of all shellfish beds are closed due to contamination. Oysters face many other threats as well. Antifouling paints containing copper can alter the growth of oysters as well as cause the shell to thicken and oxygen consumption to increase. The high sulfite content discharges by pulp mills in the Pacific Northwest are also known to reduce survival and growth of oysters. In addition, siltation and turbidity resulting from logging and onshore development can cause early larvae mortality. Dredging of estuaries has also severely restricted the areas available for successful production.

ECONOMIC VALUE: Introduced in the early 1900's from Japan, Pacific oysters quickly grabbed a foothold in North America's growing aquaculture industry. In fact, the Pacific oyster is Washington's most valuable shellfish resource. Important spawning beds are located in Puget Sound, Hood Canal, Grays Harbor, Tillamook Bay, Coos Bay and Morro Bay.