"Balanus improvisus" is the first benthos species which spread from the Black Sea in the early 20th century and settled in the Sea of Azov. Its current density is 7 kg/m2. From 1956, "Rapana venosa" is observed in the Sea of Azov, but it could not adjust to low salinity and therefore is limited to the neighborhood of the Kerch Strait. Several Sea of Azov mollusks, such as shipworm ("Teredo navalis"), soft-shell clam ("Mya arernaria"), Mediterranean mussel ("Mytilus galloprovincialis") and "Anadara inaequivalvis", originate from the Black Sea. Another example of invading species is the Dutch crab "Rhithropanopeus harrisii" which is observed both in saline and freshwater parts.