Cobia, Rachycentron canadum, is a widely distributed species from the Indo-Pacific waters to the southern Atlantic Ocean. In
Vietnam, it is an indigenous and an ideal species for cage culture. Due to its high market value in both domestic and
international markets, the technology for its culture has rapidly developed in the past few years. For its sustainable
development, there is a need to determine the carrying capacity to avoid negative marine environmental impact in the future.
This study was worked out to collect water samples when the beginning and the end of period culture at four points around the
farming area in Rachvem, Phuquoc Island, Kiengiang Province in February and October, 2011. Nitrogen and phosphorus are
examined as the principal nutrients indicated by the cobia fish farm. This study found that the carrying capacity for fish cage
farming in the area is 290.96 to 727.81 tons (based on total nitrogen) and 428.64 to 1,383.88 tons (based on total phosphorus) in
February and October, 2011. The maximum number of cobia cages was identified from 64 to 266, based on total nitrogen and
from 94 to 253, based on total phosphorus. Moreover, this study examined the possibility geographic information system (GIS)
technique due to multi-criteria to specify the most suitable sites for Cobia fish culture in Phu Quoc Island. Ten criteria were
developed into three sub-models including biochemical, socio-infrastructural and constraints with corresponding data
represented either as factors or constraints. About 1.65% of the potential area was shown the optimum locations for Cobia fish
farming. Approximately 6.228,1 ha (15.39%) could be distributed as high, moderate and less suitable sites for Cobia fish
culture and the remaining area (84.61%) was seemed not suitable for site locations. Existing Cobia fish farming covers about
36.66% of the area detected as suitable by comparing field verification data with suitability model outputs.
Keywords: carrying capacity, GIS, multi-criteria, suitable sites, Cobia fish farming.