Remote sensing images can provide wealth of information on marine environment. The capability of sensors to see through the water column, up to a certain depth below the sea level, has enabled the examination of submerged habitats. The depth of penetration of light varies from area to area and depends on the characteristics of water, atmospheric condition and so on. Present day satellites collect very high resolution images which give insight into complex physical and biogeochemical processes. Marine sciences need to consider environmental interaction of several factors and thus, the study marine processes demands integration of huge volume of multidisciplinary data collected through remote sensing, acoustic as well as traditional field observation. GIS provides the appropriate platform for such integrated analysis.

For the present study, two types of satellite data have been used;
   a) High resolution Color orthophots
   b) Medium resolution ASTER (Advanced Space-Borne Thermal Emission & Reflection Radiometer) image

High resolution color orthophotos have been used to identify marine habitats in the shallow, intertidal areas. For the subtidal areas, ASTER image has been classified using computer based automated classification method. In this method, computer groups a number of contiguous pixels into a cluster based on spectral similarity.

• 0 to 1 m
• > 1-3m
• > 3-5m
• > 5-8m

The image classification was restricted to a depth of 8m because remote sensing signal is generally poor beyond this depth in Bahrain’s territorial water. Finally the image was classified using supervised classification. The initial output image of classification often exhibits speckled appearance due to small clusters of pixels. These “speckles” were reduced by applying digital filters. Image processing was done using ERDAS Imagine software. The final output produced was a habitats’ classification map with an overall accuracy of 81 % for the habitats falling in the shallow area (0 to 3 meters), and 75 % accuracy for habitats falling in the deeper water areas (> 3 meters). These accuracy results are considered to be very acceptable considering the complexity of the marine environment in Bahrain.

The Ecological Value Index or Eco-value Index (EVI) provides an effective decision support tool for assessing and reporting the “relative” ecological significance of the off-shore areas, in geographic context. The end-result is a GIS-based assessment tool that can be integrated into research, decision-making and planning. the EVI analysis was performed using several information layers in Arc GIS software.

Four types of data layers were used as input to produce the final EVI. These data layers are;

• The marine habitats classification maps
• The fish-catch maps,
• Distribution of Endangered species
• Distributions of seabirds on Bahraini shores.

A multi-criteria approach was used for the derivation of the eco-value index (EVI) map. Four different criteria were used for the analysis of the marine habitat attribute layer, namely biodiversity, rarity, vulnerability and recoverability, two criteria for the fishing grounds (i.e. productivity and diversity), and one each for the quality for the sea-bird areas, and for the areas of endangered species. In the case of sea-bird habitats, the areas were assessed according to their breeding, nesting and resting importance for the bird, while in the case of endangered species, the criteria evaluated was the number of animals and sittings recorded by earlier investigators, in each area. A scoring scale was then applied to each criteria (for each attribute) reflecting its ecological and biological importance based on a scale of 1 to 5 (1= low, and 5 = high). Three scenarios were analyzed. For each scenario, a different data combination and weight factors were used (to give more weight for one data layer over the other).

The final results (for all scenarios) produced EVI values which were almost similar with only minor changes in their spatial distribution. Based on this analysis, the system identified the following off-shore areas as being most important (arranged from north to south):

• Fasht Bulthamh
• Hayr Shtayah
• Part of Fasht al Jarim
• Most of Fasht al Adhm
• Areas south of Fasht al Adhm to Hawar island

The importance of these areas is associated with the diversity of their habitats, the fisheries production, and their significance for endangered marine species and sea birds. The study stresses on the ecological importance of these areas, and in particular Fasht al adham and the region south of it (due to its importance as habitats for Dugongs and other marine species). Furthermore, the study emphasizes on the urgent need to give these areas a high priority in any marine environmental conservation program.