Modern status and biological aspects of Veined Rapa Whelk (Rapana venosa) in the North-East Black Sea

Abstract

Veined rapa whelk (Rapana venosa) was first recorded in the Black Sea in 1947 near Novorossiysk and by the 1970s it spread along the whole Black Sea coasts. In this time interval the rapa whelk population was stabilized in number and during the 1980s its annual fluctuations depended only from climate changes. In recent years we have observed a decrease in rapa whelk size, its earlier spawning and larval settling on submerged substrate and flattening of regional morphological changes. Based on the data analysis for 1970-2010, we offered the hypothesis that the changes in the rapa whelk biology had occurred owing to the change of the lecithotrophic larval development pattern from the years of abundant food supply to the planktotrophic one in the years with low feeding benthos mass.