| Abstract | Land use and land cover change (LUCC) is an essential environmental process that should be detected and monitored to provide a basis assessing alternatives for better land manag ement. It is necessary to evaluate land use / land cover changes to develop efficient management strategies. Remote sensing data have been extensively used for change detection in recent decades . T his study employs image enhancement of LANDSAT TM and ALOS AVINR imagery to monitor the changing status of coastal resources including land use/land cover and seagrass beds from 2001 to 2011. Post classification was used for classify of change detection. A high - resolution THEOS image was used to extract Cobia fish culture sites with an object - based classification and a KOMPSAT - 2 image was used to determine Babylon snail culture sites in the Northern part of Phu Quoc Island in 2011 . There were five classes of land use/land cover covering the study site: natural fore st, melaleuca forest, agricultural land, peat, and built - up areas. The coastal land use change from agricultural land and melaleuca forest into built - up areas is 349.89 hectares ( 51.13 % of the total area changing) . The benthic habitat with seagrass beds ha s increased from 8,618.31 hectares in 2001 to 12,869.83 hectares by the end of 2010 . The present study exhibits great potential for using remote sensing and geographic information system techniques to detect not only land use but also aquaculture sites and monitor environmental quality. It also shows some technical steps that can enhance the change assessment or influence its accuracy. Although the preliminary results of this work seem promising, further study is required to improve classification results i n coastal areas specially using an object - oriented image classification method with very high - resolution (VHR) satellite imagery. The result shows to detect land use and land cover changes in coastal area during 10 year S and locate aquaculture sites for fi sh cage and snail net pen culture to support and manage for decision making in Phu Quoc Island , Vietnam . Moreover, land use changes in coastal area and the i ncreasing growth in the marine aquaculture industry p resents new challenges in coastal management and environment . Marine cage aquaculture produces a large amonut of waste that is released driectly into the environment. To effectively manage the marine cage aquaculture environment, it is important to specified the carrying capacity of an aquaculture ar ea. This study was concerned with Cobia fish cage and Babylon snail net pen cultures as one of the sources directly affecting aquatic life and water quality in coastal environments. N itrogen and phosphorus are the principal nutrients released by the fish c age and net pen farms. The study was carried out at four different stations in fish cage site from February to October in 2011 and snail net pen culture site from May to August in 2011 . Some of the parameters such as temperature, pH , salinity and dissolved oxygen were estimated in the field while nitrogen and phosphorus, the main parameters for estimating carrying capacity, were analyzed in the laboratory. During a nine - to ten - month period (from February to October), the results in the Cobia farming area o f Rach Vem hamlet showed carrying capacity for total nitrogen and phosphorus parameters were determined from 290.96 to 727.81 tons and from 428.64 to 1,383.88 ton , respectively . For the samples taken in a three - to four - month period (from May to August) fo r a snail farming area in Cay Sao hamlet, the carrying capacity estimates of total nitrogen and total phosphorus were estimated from 7.4 to 12.85 tons and from 13.54 to 19.24 tons , respectively . According to regression analysis results, the maximum number of Cobia cages can range from 64 to 226 based on total nitrogen and from 94 to 429 based on total phosphorus; and the maximum number of snail nets can range from 130 to 171 net pens based on total nitrogen and from 238 to 256 net pens based on total phosph orus. As a precautionary measure, the maximum number of Cobia fish cages and Babylon snail nets pen should be based on total nitrogen data. T his information could be used by decision - makers to contribute and support sustainable development planning for Cob ia fish and Babylon snail culture sites and maintain the coastal ecosystem in Phu Quoc Island in the future by avoiding negative marine environmental impacts . Lastly, production of aquacultural increase to support coastal community and exported products w as estimated. To sustain aquacultural productions, finding suitable sites is an important step for aq uaculture operations. The right site selection in aquat ic farming operation is vital because it can large ly effect economic viability by estimation capital outlay, running costs, rates of production and mortality parameters . T his study aims to identi fy the most suitable sites for Cobia cage and Babylon snail culture s in Phu Quoc Island using geographic information system (GIS) - based multi - criteria evaluation models. Eight thematic layers were classified into two basic categories for Cobia fish and Babylon snail culture, namely biophysical (i.e., temperature, salinity, ba thymetry, sewage discharge and botton sediment ) and social – infrastructural (i.e., distance to local markets, distance to road and ship port ) parameters. A constraint layer was used to exclude seagrass meadows and tourism areas from suitability maps for Cobia fish and Babylon snail aquaculture development. A series of GIS models using a multi - cr iteria evaluation (MCE) technique, known as the weighted linear combination (WLC), was defined the most suitable areas for Cobia cage and Babylon snail culture sites. Suitability scores were ranked on a scale from 1 (least suitable) to 4 (most sui table). O f the potential area, 1. 6 5% and 9 . 54 % had high and moderate scores (i.e. , scores 4 and 3), respectively for Cobia culture ; and 1 . 22 % and 0.75% of the potential area had a high and moderate score (i.e., scores 4 and 3) for Babylon snail . The amount of area in this region shown to have the optimum conditions for Cobia cage culture was about 11.19% (4,529.84 ha) and for Babylon snail culture about 1.97% (798.12 ha) . The final suitability model outputs were consistent with field verification data. The available ar ea for Cobia culture sites cover about 15 . 39 % of the area for Cobia cage and only 13.08 % for Babylon snail with scores of 2, 3 and 4; it was not included unsuitable class (scores of 1) with 8 4 . 61% and 86.92 % for Cobia cage and Babylon snail culture, respec tively. This helps confirm that the developed spatial GIS model works effectively for recognizing the most suitable areas for marine culture development. This study also shows that appropriate information from GIS can be used as a powerful tool for decisio n making for selecting Cobia cage and Babylon snail culture sites. As more data become available, either from satellite images or field measurements, the benefic of this tool will increase and supply a range of functions that could be adjusted to optimize s ite selection in the future. This result shows spatial suitable regions to expand areas for the increasing growth of these species in the coastal aquaculture industry for aquaculture sustainable development |