Resurgence of massive occurrence of the invasive polychaete Ficopomatus enigmaticus (Fauvel, 1923) in the Caspian Sea

This report highlights the first substantial occurrence of the polychaete Ficopomatusenigmaticus in the Caspian Sea after nearly six decades. This taxon was observed onthe southern coasts in the harbour zones of Bandar-e-Anzali and Anzali Trade Indus-trial Free Zone. Most recently, the densities of F. enigmaticus have gradually increasedin the marina of Caspian port in the Anzali Trade Industrial Free Zone, covering thecanal walls from April 2022 to August 2023. However, successful settlement in Ban-dar-e-Anzali was not observed, probably due to the discharge of fresh water, which de-creased salinity. The average dry mass of reefs and worms was reported as 840 and 4.4g/m 2, respectively, with the maximum total dry mass of the reef reaching 1.75 kg/m2 inAugust 2023. These reefs created habitats for other macrofouling organisms, includingpartly exotic polychaetes, bivalves and crustaceans. They also provided shelter for mo-bile representatives of Amphipoda, Mysida and Decapoda. This study suggests thatenvironmental change in the Caspian Sea ecosystem may contribute to an increase inthe presence of F. enigmaticus

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