Biological invasions are recognized as one of the main environmental threats for the conservation of marine biodiversity worldwide. The alien crab Percnon gibbesi was cited for the first time from Linosa (Italy) in 1999 and later in many other locations across the Mediterranean Sea.

This study assessed the distribution of P. gibbesi and its relationships with other benthic invertebrate species in the marine reserve of Cabo de Palos – Islas Hormigas (Spain, Mediterranean Sea) and neighboring non-protected sites.

The authors found no significant influence of protection measures or insularity on the abundance of P. gibbesi. Being its colonization success closely related to the presence of small holes, encrusting algae and low slope.

The results show that the abundance of P. gibbesi was similar to that of native crab species; however, a non-significant negative relationship between the abundance of P. gibbesi and native crabs (Pachygrapsus marmoratus and Eriphia verrucosa), urchins (Arbacia lixula and Paracentrotus lividus) and a snail (Phorcus turbinatus), all of them herbivorous species, was observed.

The authors underpin that the results of the study may indicate the future scenario and potential negative effects over native species abundance, and thus highlight the importance of establishing a long-term monitoring program to evaluate the population increase and spread in the region, taking spatial variation of structural habitat at different scales into account.

Félix-Hackradt FC, Sanchis-Martínez AM, Hackradt CW, Treviño-Otón J, García-Charton JA(2018) Distribution and ecological relations among the alien crab, Percnon gibbesi (H. Milne-Edwards 1853) and autochthonous species, in and out of an SW Mediterranean MPA. Hidrobiologia 806:187-201.