Native Littleneck clam     Protothaca staminea


Japanese Littleneck clam        Venerupis philippinarum



These two clam species are considered together because they live in the same habitat, have similar anatomy and are easily confused.  The Japanese Littleneck clam (it used to have the common name of Manila clam, but the official common name was recently changed to Japanese Litteneck Clam) on the left in the photograph was introduced in the area when the first Pacific oysters from Japan arrived.  They, along with a number of other species of plants and animals , were hitchhikers and found our area to their liking.  However the Japanese Littleneck clam cannot tolerate the wide temperature changes in our area and  experiences seasonal die-offs on occasion.  Like all clams they are filter feeders eating the small plants and animals called plankton that float in the water column.


The Native Littleneck on the right has an almost oval shell with numerous vertical and horizontal ridges on the shell, the inside margin of the shell is rough and the two siphons are fused at the tip.  The Japanese Littleneck clam shell is more elongated with prominent ridges, a smooth margin on the inside of the shell and the siphons are split at the tip.  Both species can have variegated color patterns on the shell and are about the same length at maturity. 


Both occur near the surface (digging to 4 inches deep) in sandy,mud/gravel beaches from the mid intertidal to just below the low tide line, although the Manila tends to live at slightly higher tide level.  While the Native Littleneck ranges from the Aleutian Islands in Alaska to Baja California, the introduced Japanese Littleneck clam is found from the central coast of British Columbia to central California. 


Because they live near the surface they are both vulnerable to attack by Moon snails, sea stars, crabs, fish (nip their siphons) gulls and crows.  Both gulls and crows will grab a clam, fly up in the air and then drop it on the beach breaking the shell.


They breed from late spring through mid summer by releasing eggs and sperm into the water column where fertilization occurs.  The young, called a Veliger larvae, stay in the plankton for several weeks finally settling to the bottom in the near shore area.


Both species are cultured in our area growing to market size of 1.25 inches in 3-4 years, but the Japanese Littleneck clam is the most popular.  Farmed clams had a market value in 2000 of around $14 million.


Be sure and check with the local health department prior to digging to see if your chosen beach is closed due to shellfish poisoning or pollution.  Also check current state regulations concerning the digging and possession of shellfish.