Habitat Suitability Index Demonstration Model

This Habitat Suitability Index (HSI) evaluates the impact of salinity alterations on oyster habitat. The user defines the area of interest and specifies the percent of bottom covered with suitable cultch. The salinity data requirements of the model are monthly means for a year. From monthly means the mean salinity during the spawning season and an 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.

Percent of Bottom Covered With Suitable Cultch

Bottom coverage of an area with a suitable hard substrate (e.g., oyster shell, clam shell, limestone) of ≥ 50% is considered optimal. No coverage of the bottom with suitable cultch is unsuitable.

Mean Salinity During the Spawning Season

Optimal salinities in the spawning season are higher than those for adult survival. Mean spawning-season salinities of 18-22 are considered optimal, whereas salinities ≤ 5 and ≥ 40 are unsuitable.

Minimum Annual Salinity

Extremely low salinities (≤ 2) cause mass mortalities of oysters. A single monthly mean of ≤ 2 is unsuitable; as a minimal salinity ≥ 8 is not considered detrimental.

Annual Mean Salinity

The optimal annual mean salinity is between 10 and 15. Values ≤ 5 and ≥ 40 are unsuitable

Habitat Suitability Index: