The Rapa whelk Rapana venosa is an important commercial gastropod species in Turkey. This paper explains population biology of this species in the aim to ensure the sustainability of this resource. Rapa whelk samples were collected monthly from April 2006 to February 2007 by dredge in the South eastern Black Sea of Turkey (in heavily and lightly exploited areas). The size of whelks ranged 7.56-116.14 mm. The sex ratio F:M is 1:6 in Trabzon and 1:1 in Samsun. The individuals in Samsun region are larger than Trabzon. Female whelks are significantly smaller and lighter than males in both areas. The maximum density was observed to be 12.3 t.km(-2) in summer at Samsun. The most by-catch species are blood cockle Anadara inaequivalvis (Bruguiere, 1789) and shore crab Liocarcinus depurator (Linnaeus, 1758).