Distribution, abundance and colony size of the invasive coral Oculina patagonica de Angelis, 1908 (Cnidaria, Scleractinia) in Malta

Abstract

The zooxanthellate, scleractinian coral Oculina patagonica is known from various locations in both west and east basins of the Mediterranean Sea, but there are only three casual records of this cryptogenic species from the Central-Ionian area, all from Malta in 2017. Surveys at 28 sites around the Maltese coasts undertaken during the present work revealed 43 colonies spread across ten sites. The coral occurred primarily on artificial substrata in harbour areas at depths shallower than 6 m, but a few colonies occurred on natural rocky bottoms and in non-harbour sites. The largest colonies reached a mean diameter of up to 95 cm and occurred on artificial structures that are only a few decades old, while the majority of the colonies were much smaller (< 40 cm diameter). This, together with the clustering of records in harbour areas, suggests that O. patagonica was likely introduced in Maltese waters in recent decades via maritime transport. The present results also confirm that this species is established in the Central Mediterranean area.