First record of brush-clawed shore crab Hemigrapsus takanoi (Asakura and Watanabe, 2005) in the Gulf of Gdańsk (southern Baltic Sea)

Abstract

The first occurrence of the brush-clawed shore crab Hemigrapsus takanoi was recorded during the monitoring of non-indigenous species carried out in the Port of Gdynia (Gulf of Gdańsk) in 2023. The discovery is important as it indicates an expansion of the biogeographic range of this crab in the southern Baltic Sea. Two males with carapace widths of 12.1 and 21.51 mm and wet weights of 3.32 and 6.88 g, respectively, were collected using a Fukui box trap and a self-designed habitat collector. Although H. takanoi is considered a successful invader, according to previous studies, the expansion of this species in the southern Baltic Sea may be limited by the salinity gradient. Its early life stages show low resistance to low salinity conditions, thus precluding the establishment of self-sustaining populations of this crab.