A Preliminary Study on Crabs Diversity for Beibu Gulf Mangrove

A field study had been conducted to identify the brachyuran crabs in the 12 sampling stations in mangroves of Beibu gulf during July to October 2012. A total of 39 species of brachyuran crabs belonging to 11 families,23 genera were reported. Among these species,Perisesarma eumolpe was a new record in China,and P. maipoensis was a new record in Hainan; Ocypodoidea( including 8 genera and 20 species) was accounted for 51. 3%,and Grapsoidea( 10 genera and 14species) accounted for 35. 9% of all species; There were also two species of Portunidae and Pilumnidae,respectively; and one species belonging to Leucosiidae. Among the 12 sampling stations,the diversity index of crabs( H') ranged between1. 861 ~3. 315,with a mean of 2. 641,the highest Pielou index value( 3. 315) was observed in Beihai Caotou village,while the lowest( 1. 861) was in Hainan Qinglan Harbor; Pielou index( J') ranged between 0. 587 ~ 0. 829,with a mean of 0. 727,the highest was observed in Beihai Caotou village,while the lowest was in Qinglan Barbor; Margalef index( D')ranged between 0. 892 ~ 1. 972 with a mean of 1. 448. The similarity index ranged between 0. 087 ~ 0. 632,the maximal value( 0. 632) was observed in both Daguansha and Leizhou Haijiao village; The lowest similarity value( 0. 087) was observed in both Hainan Qinglan Barbor and Beihai Caotou villege. The results showed that Ocypodoidea and Grapsoidea were the largest groups,and the Beibu gulf coastal mangrove crabs belonged to the South China Sea crab fauna which was composed of tropical and subtropical warm water species and wide temperature species. The composition and distribution of the crab could be influenced by the different mangrove vegetation,latitude,salinity,temperature,substrate,tidal and other comprehensive factors.