Common Littleneck Clam

Photo: D. Cowles^[1]

Taxonomic description

• Size: Mean (±1SD) length 2.94 ± 0.22 cm; maximum length of around 6.35 cm. ^[1]
• Color: range varies by habitat; yellowish gray to gray in sloughs and bays, porcelain-white with wavy brown marks in the open coast.^[2,4]
• Radiating bands and very closely spaced radial and concentric ridges.^[1]

Distribution

• From the Aleutian Islands, Alaska to Cape San Lucas in southern Baja California, Mexico.^[1,7]
• Common in California including Mission Bay and Tijuana River Estuary connecting Mexico and the United States.^[5] 

Life history

• Separate sexes (dioecious) with some hermaphroditism reported.^[4] 
• Actively spawns in warmer months (June to September). Ideal temperatures for spawning are around 22-30 ℃; Spawning is interrupted when temperatures fall below 24°C. ^[3]
• External fertilization; Gametogenic progression in male and female clams is categorized by five stages: inactive, gametogenesis, ripe, spawning and spent.^[3,7]
• Females may spawn several times during a season, while individual males release all gametes at once.^[4]
• Embryos develop into free-swimming trocophore larvae that resemble a small clam prior to settling. Larval (pelagic) duration is 3-4 weeks and larvae are 260-280µm in length at metamorphosis.^[4,5] 

Habitat

• Predominantly found in the middle and low intertidal zones.^[2,8,9]
• Higher abundance in areas with fine/very fine sand, or sand-silts with lower abundance in sediment containing clay.^[2]
• Can be found in very course sediment to fine sand, with higher densities occurring in finer sand.^[1,5] 
• In California, found in sand/mud sediments in bays, sloughs, and estuaries. North of California, found in high density where cobbles overlay sandy bottoms on the open coast.^[7]
• Gastric content observed to be only phytoplankton.^[8]

Seasonal availability

• Available year-round

Regulatory and Managing authority

• The California Department of Fish and Wildlife (CDFW) requires clam diggers to have a valid sports fishing license. For wild harvest, there is a size limit of 1.5 inches diameter at the greatest shell width point.^[11]
• Aquaculture operations are subject to approval by the California Department of Fish and Wildlife and/or the Fish and Game Commission. Permitting is complex and involves multiple state, federal and local agencies, and varies with species, location and more.^[12] 
• The Permit Guide to Aquaculture in California outlines the permitting and registration process.^[12] 

Gear type

• Besides using hands and feet to dig through the sand, rakes and shovels are also common.^[13]

Status of the fishery

• There is no established commercial fishery for common littleneck clams in California.
• Legal recreational catch size limit is 3.8 cm (1.6 in) shell length, reached at about 4–5 years old. Southern California clams may reach the minimum legal harvest size sooner than other areas.^[4,8]
• Grow to a harvestable size in four to six years in Washington state where they are routinely farmed from wild stock, as hatchery seed is generally unavailable in WA.^[14]
• Ideal conditions for rearing larvae are 10–15˚C and salinity of 32 ppt.^[4]
• Growth is often slow in early years on exposed beaches and becomes more rapid in later years, but the opposite may be true for individuals in protected sites. Growth in protected clam gardens has historically been found to be up to 1.7x faster than in the wild. ^[4,15]

Potential ecosystem impacts

• Wild harvest requires digging up substrate which can have localized, temporary impacts from the disturbance.
• Operation impacts from aquaculture of this species are considered minimal. Clams subsist on plankton filtered out of the water and therefore require no feed. Additionally, effluent water at culture sites is highly regulated.^[11] 

Edible portions

• The entire soft-bodied clam is edible. ^[12]

Description of meat

• Sweet, tender and chewy-textured.^[16] 

Culinary uses

• Take only minutes to cook, and can be served alone or as a highlight in a dish.^[17] 
• Most often steamed. 
• Can be included in pastas, soups, or rice. 

Nutritional information 

• Dairy-free
• Low fat
• Paleo friendly
• Keto friendly

Nutritional chart from Whole Foods Market.^[18]

Toxicity report

• Clams have the potential to naturally accumulate domoic acid toxins, which can be a health hazard for human consumption. The The California Department of Public Health provides updated shellfish advisories^[19]
• Farmed shellfish undergo depuration (time in clean water to clear any contaminants) and are tested for safety before being sold. 

Seasonal availability

• Available year-round. ^[11]