The current status of the alien ascidian Herdmania momus in Malta

Abstract

The non-indigenous ascidian Herdmania momus was first recorded from the southeast coast of Malta at Marsaxlokk in 2013. Surveys at eight sites along the east coast of Malta revealed that it has since spread to another two sites, one of which is located ca 10 km north of Marsaxlokk. The ascidians remain largely restricted to artificial substrata in areas under anthropogenic influence, although a few individuals were observed on natural rock. The size distributions of the three populations reflect the likely propagation of the tunicates from the site of introduction. Four taxa of commensal crustaceans inhabiting Maltese H. momus were found, with the highest abundance of ascidicolous crustaceans recorded from the Marsaxlokk population.