This paper describes the use of GIS modeling to identify and quantify aquaculture opportunities in a polluted bay. The models were arranged to evaluate the bay in terms of fish and mollusk culture, and the principal culture species selected were the turbot Psetta maxima and mussel Myalus galloprobincialis. Baseline topographic data was extracted from a Landsat TM image of Izmit Bay acquired in 1996. Other secondary data was collected in the form of hard-copy maps and field data for water quality at a series of stations in the bay. This data was prepared for use in ArcInfo software. The results indicate that a high percentage of Izmit Bay waters are not suitable for aquaculture. The pollution in the area is causing some environmental concerns at the present and more expected in the immediate future. However, the preliminary models constructed indicated that some of the bay could be developed for aquaculture. An area of 725 hectares in the western part of the bay was classified as being suitable for turbot culture and area of 5,150 hectares in the western part of the bay was considered suitable for mussel culture.