This Habitat Suitability Index (HSI) evaluates the impact of salinity alterations on oyster habitat. The user defines the area of interest and determines the percent of bottom covered with suitable cultch. Minimum salinity requirements of the model are monthly means for a year. From monthly means the mean salinity during the spawning season, and annual mean salinity are calculated. Minimum annual salinity is the lowest mean monthly salinity in the annual record. This HSI is thus an evaluation of a single site (area) for a single year, without reference to historical trends. An application of the model is to compare HSIs for a site within a year calculated with and without salinity alterations.