Does the introduced polychaete Alitta succinea establish in the Caspian Sea?

Members of the polychaete family Nereididae do not occur naturally in the Caspian Sea but are documented intentional human introductions that commenced in 1939. However, the identity of the species involved has been uncertain; material has been identified as both Alitta succinea and Hediste diversicolor. In this study, we confirm the presence of both species in the Caspian Sea. We discuss the distribution of both species, based on tolerance to physical factors, especially salinity. Although establishment of this partially predatory Nereidid, as a food reservoir could facilitate the recreation of commercially exploited fish stock, the consequences for native benthic communities are unclear and may be subject to unforeseen negative impacts.