Spreading of invasive bivalves Anadara kagoshimensis and Anadara transversa in the northern and central Adriatic Sea

Two non-indigenous invasive bivalve species, Anadara kagoshimensis (Tokunaga, 1906) and Anadara transversa (Say, 1822), were recorded for the first time in the open waters of the eastern Adriatic Sea trawling grounds. Samples of these species were collected in 2008-2011 with modified beam trawl (rapido) during the SoleMon project, a project aimed at investigating the northern and central Adriatic Sea. In the years following its first record in 2008, the abundance of A. kagoshimensis increased in the area of investigation off the Istrian coast. The highest recorded abundance index per station was 1089 N km(-2) in 2011. Species was present at depths from 31 to 41.5 m. Presence of Anadara transversa was recorded only at one station in 2011, in the middle of the open Adriatic between 70 and 72.5 m depth. The possible vectors of invasion of these species, from the western Adriatic coast to the eastern, are discussed.