A field test of the American oyster habitat suitability (HSI) model

The HSI model, developed by Cake (1983) for the American oyster, has been field tested on 38 0.1 hectare reef and non-reef sites in Galveston Bay. The HSI is dependent upon 6 (HSI1) or optionally, 8 variable (HSI2). The variables of the model are percent of bottom covered with suitable cultch, mean summer water salinity, mean abundance of living oysters (a gregarious settling factor), historic mean water salinity, frequency of killing flood and substrate firmness. The optional variable are density of southern oyster drills and intensity of Perkinsus marinus . The HSI1 values of reef and nonreef sites are significantly different and the model is capable of distinguishing where oysters are found from areas where they are absent. HSI1 values from reef sites are correlated with oyster density. HSI2 values from ree sites were not correlated with oyster density. Despite differential harvesting pressure, reef sites with highest HSI values tended to have greater densities of oysters, as predicted by the model