Rapa whelk controls demersal community structure off Zmiinyi Island, Black Sea

Abstract

Between 2004 and 2012, populations of Mediterranean mussel (Mytilus galloprovincialis) and rapa whelk (Rapana venosa) from the coastal waters of Zmiinyi Island (Black Sea) were assessed for distribution, abundance, size, and age characteristics. Compared to 2004–2005, the mussel bed cover in 2012 decreased by 75.6%, the maximum depth of occurrence reduced from 22–25 m to 10–12 m, and total biomass declined by 44.6%. There was a concurrent decrease in abundance of demersal fishes dependent upon mussels as prey. We concluded that the invasive rapa whelk has had a detrimental impact on this demersal ecosystem. The possible influence of the introduced ctenophore Mnemiopsis leidyi on the two mollusc’s populations has also been discussed.