Status of the Rapa Whelk Agglomerations Along the Romanian Black Sea Coast

Abstract

The Black Sea Rapa whelk (Rapana venosa, Valenciennes 1846) is, on one hand, a non-indigenous species harming Black Sea benthic ecosystem and on the other hand, since its ever-expanding stock found market in the Far East, one of the most profitable in the basin.
For this purpose, the Working Group on the Black Sea (WGBS) under General Fisheries Commission for Mediterranean and Black Sea (GFCM) agreed on the fact that, despite the invasive nature of the species, its stock in the Black Sea should be exploited within biologically safe limits. In order to cover the area of study in high percentage, a number of 51 stations were proposed for Romanian coast, that were distributed evenly. The duration of one haul was 30 minutes and the hauls were performed at a constant depth and rectilinear in a big percentage, but to avoid tangles and gear destruction, some deviations have been made. Age composition in 2020 was formed by 3 to 12 years generations, the percentages were recorded for 6- and 7-years classes. Regarding 2021 data, the age composition was composed by 3 to 11 years, with the numbers recorded for 5- and 6-years classes. Highest abundance and biomass values for rapa whelk in 2020 have been recorded in the north part of the Romanian coast in the sectors Zaton, Sahalin, Sf. Gheorghe and Mila 9. For 2021, data no significant changes were observed.