PERIWINKLES PROGRESS - THE ATLANTIC SNAIL LITTORINA-SAXATILIS (MOLLUSCA, GASTROPODA) ESTABLISHES A COLONY ON A PACIFIC SHORE

The common ovoviviparous and eurytopic Atlantic Ocean periwinkle Litto rina (Neritrema) saxatilis (Olivi, 1792) has established reproducing p opulations in San Francisco flay, California, USA. The first populatio n was discovered in 1993. The probable mechanism of introduction into the Bay is the disposal of seaweeds (the brown algae Ascophyllum nodos um and Fucus vesiculosus) used as transport packing with polychaete wo rms used for fish bait. These worms, seaweed, and associated periwinkl es originate from Maine. An alternative mechanism may be the similar d isposal of seaweeds used as packing for imported Atlantic lobsters (Ho marus americanus) for the restaurant trade. Littorina saxatilis could occupy a range on the Pacific American coast from Baja California to w estern Alaska, and as such it would come into direct contact with the consubgeneric Littorina (Neritrema) subrotundata (Carpenter, 1864) (sy nonym: Littorina newcombiana Hemphill, 1877) and Littorina (Neritrema) sitkana Philippi, 1846, which occur from southern Oregon and north. T hese latter two species occur in a range of morphological-physiologica l ecotypes that are closely analogous to those of Littorina saxatilis. Eradication of this snail invasion may be possible because the popula tions are easily accessed and relatively small. However, no tested era dication methods are known, nor are jurisdictional authority or regula tory issues clear relative to initiating potential removal of this spe cies.