Abstract
The California salt marsh snail Melampus olivaceus, a species from southern California, has established a thriving population in the Elkhorn Slough estuary (Monterey Bay), hundreds of kilometers north of where it is long-established and regularly found. Since the late 1800s this high littoral zone salt marsh snail has occasionally been reported in central California, but only as isolated individuals or shells. We first observed a few individuals of M. olivaceus in Elkhorn Slough in 2013, and the species is now abundant and reproducing throughout the estuary in Salicornia pacifica (pickleweed) marshes. We also document for the first time that this species has a planktonic, feeding larva. Salt marsh snails may have been transported northward as planktonic larvae during periodic El Niño warm water events. Such transport has been reported for other species, but what makes this case unusual is the persistence, reproduction and abundance of the snail following transport.
Highlights
The California salt marsh snail Melampus olivaceus, a species from southern California, has established a thriving population in the Elkhorn Slough estuary (Monterey Bay), hundreds of kilometers north of where it is longestablished and regularly found
The California salt marsh snail Melampus olivaceus Carpenter, 1857, is a pulmonate gastropod that lives in the high littoral zone of estuaries in pickleweed (Salicornia pacifica) and other salt marsh plants (Morris et al, 1980)
There is one record of a single empty shell of M. olivaceus found at the Salinas River mouth (Cooper 1867), about 300 km north of Pt
Summary
The California salt marsh snail Melampus olivaceus, a species from southern California, has established a thriving population in the Elkhorn Slough estuary (Monterey Bay), hundreds of kilometers north of where it is longestablished and regularly found. The historical northern range limit of M. olivaceus is somewhere to the south of Pt. Conception. There is one record of a single empty shell of M. olivaceus found at the Salinas River mouth (Cooper 1867), about 300 km north of Pt. Conception, likely collected between the years 1853 and 1866.
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