Long-Term Surveys Show Invasive Overbite Clams (Potamocorbula amurensis) are Spatially Limited in Suisun Marsh, California

摘要

The overbite clam (Potamocorbula amurensis) is amajor invasive species in the San Francisco Estuary,California, and has been implicated in the declineof pelagic productivity and native fish species. Littleis known of its impact on Suisun Marsh, a largebrackish tidal region of the estuary. We looked at theabundance and spatial distribution of clams in themarsh, including examining the influence of waterquality, using long-term (1988–2015) otter trawlsurveys. Temporal trends indicated that overbiteclam abundance has been increasing, but adult clamswere spatially restricted to a single large slough(Suisun). Clams were absent from most interiorchannels, limiting their overall effect on the marshaquatic ecosystem. Abiotic variables, particularlysalinity, proved important predictors of overbiteclam abundance, although the variables examinedalone could not explain overbite clam distributions.We propose that connectivity, detritus loads, and/or predation pressure may work in conjunctionwith abiotic variables to cause poor survival ratesfor recruits in interior marsh sites, keeping thedistribution limited. Overall results are encouragingfor restoration projects in brackish tidal marshes thatneed to deal with overbite clams.