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Competition with other crabs has been implied as an impact for Mediterranean
populations (Gennaio et al., 2006). It is also known to feed on fish caught in nets and
to damage fishing gear (Främmande Arter, 2006). The occurrence of Callinectes
sapidus could be an important harmful factor in the human health system as well as
in the tourism sector because blue crabs have been implicated as carriers of strains
of the bacterium Vibrio cholerae which are responsible for outbreaks of human
cholera (Hill et al. 1989).
There have been other claims of established populations of Callinectes
sapidus in the western and central Mediterranean Sea (Gennaio et al., 2006; Beqiraj
and Kashta, 2010; Dulcic et al., 2011; Castejón and Guerao, 2013) based on
occasional collections of adult specimens and ovigerous females. Taking into account
the current increase in the temperature of Mediterranean, and, in general, European
coastal waters (Lejeusne et al., 2010; Lima and Wethey, 2012), climate change can
be envisioned as one of the main determinants of the invasion success of Callinectes
sapidus, past and future (Hines et al., 2010). To date, biological invasions and global
warming are no longer considered independent in their effects on the biodiversity
and functioning of natural ecosystems (Walther et al., 2009); large-scale studies,
encompassing environments with a diverse range of seasonal variability in water
temperature, will provide useful information on climate-related mechanisms
regulating the occurrence of this IAS in invaded habitats.
Callinectes sapidus has been included among the 100 worst IAS in the
Mediterranean Sea (Streftaris and Zenetos, 2006); however, with the exception of
the eastern sectors of the basin, the actual spatial-temporal characteristics of blue
crab populations in non native environments have been poorly investigated, while
their functional importance and ecological impact on autochthonous communities
are to date virtually unexplored.

Xanthias lamarckii
Xanthias lamarkii is the most common species of the genus Xanthias (Serène, 1984)
(Fig. 13), with a distribution extending in the Indo-West Pacific Ocean, from Eastern
Africa (South Africa), Mauritius, Réunion, Madagascar, Europa Isl., Comoros
(Anjouan, Mayotte) to Australia, Japan, Hawaii, and French Polynesia, including
Wallis and Futuna Islands (Serène, 1984; Davie, 2002, 2012; Legall and Poupin,
2013). It is a shallow waters crab (0-100 m of depth), commonly observed in depths
of 0 to 6 m, on hard bottom (rock and rubbles) (Legall and Poupin, 2013). Xanthias
lamarckii was located in south-eastern Aegean Sea. The occurrence of this Indo-West
Pacific species was reported for the first time in the Mediterranean waters and
exhibits the on-going process of biological invasion of the basin (Corsini-Foka et al.,
2013).