Expansion of the Distribution Range and Size of the Invasive Blue Crab on the Turkish Coast of the Black Sea

The blue crab (Callinectes sapidus Rathbun, 1896) is an euryhaline species originally native to the western Atlantic Ocean. However, it has expanded its range into the Black Sea, including the Turkish coastal waters. Blue crab specimens were sampled along the Black Sea coast of Türkiye, covering the stretch from Cape Taşkana to the Georgian border. The monitoring studies spanned the period from 2017 to 2024. Analysis of the 16 specimens revealed a carapace width range of 14.8 to 20.3 cm, with males exhibiting larger sizes compared to females. Notably, two of the sampled females were observed to be carrying eggs, highlighting reproductive activity in the region. This study also reports the discovery of the largest blue crab ever recorded on the Turkish coasts of the Black Sea, with a male specimen measuring 20.33 cm in carapace width and weighing 565.1 g. Additionally, a male specimen sampled in the Rize region suggests the species has expanded its range to the easternmost part of the Black Sea. The findings contribute significantly to our understanding of the distribution and growth potential of the blue crab in the Black Sea. The larger sizes observed in males and the presence of ovigerous females indicate successful adaptation and potential establishment of a self-sustaining population. As invasive species, blue crabs can significantly influence benthic communities and food chains, highlighting the importance of a prudent management approach to fisheries biology and ecosystem management