Distribution of Decapods in the Selected Mangrove Sites in Sta. Maria, Davao Occidental, Philippines

Aims: To identify the species of decapods and their edibility, determine the population density, abundance, dominance, and diversity indices of decapods found in the selected mangrove sites, and measure the physicochemical parameters of the area.

Place and Duration of Study: Barangay Tanglad, Mamacao, and Basiawan of the Municipality of Sta. Maria, Davao Occidental. April 25-29, 2022.

Methodology: A transect-plot method was used in sampling and the samples were handpicked or captured using tongs, scooped using the locally used net, dug from their burrows, and collected from wooden hides. The samples were put in a container with seawater and ice, then cleaned, photographed, and identified. The samples were presented to the fisherfolks and locals to identify local names and their edibility. The pH, temperature, and salinity of the seawater were recorded on site. The decapods’ taxonomic classification was identified. The population density, abundance, dominance, and diversity indices were computed.

Results: There were 13 species of decapods found in the three sampling sites, namely: Triangular fiddler crab (A. triangularis), Nymph snapping shrimp (A. euphrosyne), Mud crab (B. vinosus), Forceps crab (E. dentatus), Brown land crab (C. carnifex), Hermit crab (C. rugosus), Indian prawn (F. indicus), Giant freshwater prawn (M. rosenbergii), Alamihi crab (M. thukuhar), Mudflat crab (P. pictum), Flat porcelain crab (P. cinctipes), Mangrove swimming crab (T. crenata), and Compressed fiddler crab (T. coarctata). A total of 633 individuals were gathered from the three sampling sites. 279 individuals were collected in Barangay Tanglad, 189 individuals in Barangay Mamacao, and 165 individuals in Barangay Basiawan. Triangular fiddler crab (A. triangularis), Hermit crab (C. rugosus), Indian prawn (F. indicus), Alamihi crab (M. thukuhar), Mudflat Crab (P. pictum), and Compressed fiddler crab (T. coarctata) were observed to be present among the three sites. In the three sampling sites, Mudflat crab (P. pictum) showed to have the highest population density of 199 ind./2,700 m2, highest index of the dominance of 0.291, and a relative abundance of 31.44%. Mudflat crab (P. pictum), Triangular fiddler crab (A. triangularis), and Compressed fiddler crab (T. coarctata) were the most dominant species in the area.

Conclusion: Barangay Tanglad was found to be the most diverse site, it also had the highest index of evenness. Barangay Mamacao and Basiawan had the highest similarity index. There was no significant difference in the number of decapod species between the sampling sites. The physicochemical parameters are within the optimum level which could be a favorable condition for the abundance of the decapods.