Field validation of a habitat suitability index model for the American oyster

A habitat suitability index (HSI) model, developed for the American oyster,Crassostrea virginica, along the Gulf of Mexico, was field tested on 38 0.1-ha reef and nonreef sites in Galveston Bay, Texas. The HSI depends upon six (HSI1) or, optionally, eight (HSI2) variables. The six variables are percent of bottom covered with suitable cultch (V₁), mean summer water salinity (V₂), mean abundance of living oysters (V₃) (a gregarious settling factor), historic mean water salinity (V₄), frequency of killing floods (V₅), and substrate firmness (V₆). The optional variables are the abundance of the southern oyster drillThais haemostoma (V₇), and the intensity of the oyster pathogenPerkinsus marinus (V₈). The HSI values were lowest at high and low salinity sites and highest at intermediate-salinity sites. To validate the model, the hypothesis that the output of the HSI model was correlated with oyster density was therefore tested. A significant correlation was found between HSI1 and oyster density (Kendall Tau Beta correlation coefficient, τ=0.674, p