Status of the Siberian Prawn, Exopalaemon modestus, in the San Francisco Estuary

The freshwater Siberian prawn, Exopalaemon modestus (Heller 1862, Crustacea: Decapoda: Palaemonidae), was likely introduced into the San Francisco Estuary in the late 1990s. Since the initial collection in 2000, E. modestus spread rapidly throughout the estuary and into upstream areas, and is now the most common caridean shrimp in the upper estuary, including the Sacramento–San Joaquin Delta. We summarized data collected from 2000 to 2011 by several long-term monitoring projects, special studies, and the public concerning E. modestus in California. Although some specific ecological effects of this introduced species have been documented, broader effects are largely unknown. E. modestus is likely to expand its distribution within the estuary and watershed and become established in other freshwater areas of California.