In situ observations and census of invasive mud crab Rhithropanopeus barrisii (Crustacea: Decapoda: Panopeidae) applied in the Black Sea and the Sea of Azov

摘要

Coastal areas, lagoons and river estuaries along the Crimean peninsula, Sea of Azov and Russian Krasnodar region Black Sea coast have been searched for the presence of Harris mud crab [Rhithropanopeus harrisii (Gould, 1841)] using snorkeling and SCUBAequipment. New populations were observed in 2 river estuaries (Vulan and Shap'sukho), Bugas liman adjacent to the Black Sea and it was widespread in the Taman Bay in the Sea of Azov. The crabs have been found in very distinct habitats from shallows of the Taman Bay with broad Zostera spp. meadows, to narrow reed roots bands along the river estuaries. Similar habitats between the Black and Azov seas have shown complete absence of the crab in one and presence in the other respectively. Our results show that currently no standard method that exists, can be applied to all different types of habitats that we observed in this study. Nevertheless, the method of underwater transect census allowed us to perform quantitative analysis of crabs' hiding behavior in the Taman Bay; smaller crabs of both sexes and most of ovigerous females prefer to hide in burrows. Size composition of crabs has been described for the Taman Bay and Black Sea estuary crab populations. These studies lead us to suppose that there is aseasonal migration pattern of R. harrisii in the shallows of the Taman Bay and no such observations are apparent in the estuary habitat. While distribution of different age groups and migration patterns may be very different, the general life cycle of Harris mud crab in these populations appears to be similar.