The Tar River spinymussel Potential Habitat dataset is a polygon layer depicting high, moderate and low potential habitat locations for Tar River spinymussel in NC counties.

The Tar River spinymussel (Elliptio steinstansana) is endemic to only the Tar River and Neuse River systems in North Carolina. In the Tar River system, the species has been documented from the mainstem of the Tar River, Shocco Creek, Fishing Creek, Little Fishing Creek, Swift Creek, and Chicod Creek. In the Neuse River system, the species has been documented only from the Little River. The Tar River spinymussel lives in relatively silt-free unconsolidated beds of coarse sand and gravel in relatively in fast-flowing, well oxygenated stream reaches. It is found in association with other mussels, but it is never very numerous. The primary factors affecting the species and its habitat appear to be primarily stream impacts (sedimentation, bank instability, loss of instream habitat) associated with the loss of forest lands and forested riparian buffers, and poorly controlled stormwater runoff of silt and other pollutants from forestry and agricultural (livestock and row crop farming) activities, development activities, and road construction, operation, and maintenance. Pesticides were implicated in the largest known mortality event for Tar River spinymussel. In addition to the above, point source discharges continue to threaten habitat quality in both the Tar and Neuse River watersheds.

The three levels are: Low, Moderate, and High Probability of Potential Habitat (based on similarity of environmental conditions to those found at known occurrence locations). The category thresholds were set based on the distribution of predicted values for known habitat. The High-Moderate threshold is set at the level where 90% of the observed potential habitat (species presence and reviewer judgments) falls within the High category (Presence Percent Correctly Classified). The Moderate-Low threshold were set at the level where 8% of the observed potential habitat (species presence and reviewer judgments) falls within the Moderate category and 2% within the Low category. The final thresholds for this species are 0.11 and 0.355 for the Low-Moderate and Moderate-High thresholds, respectively. Lower thresholds result in more of the range labelled as High probability of habitat and greater misclassification of known non-habitat locations. Higher thresholds result in more of the range labelled as Low probability of habitat and greater misclassification of known habitat locations.

Given the larger spatial unit of ecological models and ecological characteristics of aquatic species, the landscape scale environmental attributes of potential habitat varied greatly among sites and could closely resembled non-habitat sites. It is important to remember that potential habitat (and non-habitat) can occur at any classification level within a catchment and must be verified by a qualified biologist.

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Datasets developed under Project ATLAS do not replace any NRTR work for future projects and may not be used as a replacement for site visits / field surveys by qualified professionals and hence should be used only as a supporting platform for decision making. Use of this dataset for project scoping or screening is merely pre-decisional.