Occurrence of the non-indigenous species Dyspanopeus sayi (Crustacea: Brachyura) in a Mediterranean coastal lagoon (S. Gilla, Southern Sardinia).

Introduction of non-indigenous species (NIS) represents a worldwide threat to the integrity of the native communities, altering the natural distribution of the biota and impacting biodiversity. The Medi¬terranean Sea has been exceptionally susceptible to biological invasions and it is considered the world’s most invaded sea, hosting currently more than 700 NIS. Among the Mediterranean NIS, the mud crab Dyspanopeus sayi (Smith, 1869), native to the Western Atlantic, was recorded only in recent years. The first record was from the Venice lagoon in 1991, where nowadays, it is the most common crab species. Most probably, it was introduced by shipping, as larvae in water ballast or accidentally through exchanges of aquaculture products. Since then, the species has spread into other areas, colonising different locations across the whole Mediterranean Sea. We report here the first record of this species in a Sardinia lagoon (Santa Gilla lagoon, Southern Sardinia), obtained from samples collected during the investigation of the macrozoobenthic communities. Six stations were screened during four surveys, and three male specimens of the NI crab were found in the central area of the lagoon. The few records suggest that the introduction of the species could have been a recent event. However, as the sampling method used was not appropriate to collect vagile species like crabs, we cannot infer on the abundance of the species in this lagoon. This finding, however, deserves particular attention since, within its native range, it is a common predator of shallow water bivalves. Moreover, in the Adriatic Sea, D. sayi has exterminated different prey mollusc species in a very small locally restricted area. We pinpoint here that, since the Santa Gilla lagoon is an im¬portant site for shellfish farming and aquaculture of commercial value bivalves species, an accurate search for abundance and potential impact of D. sayi on this lagoon is needed.