A national assessment of landscape influences on riverine fishes of the conterminous United States

One of the near-term objectives of the National Fish Habitat Action Plan is to conduct an assessment of the condition of U.S. fish habitats to facilitate allocation of resources for habitat protection, enhancement and restoration.  To help meet this objective, we examined the direct and indirect influences of landscape sources of stress on fish community metrics that are responsive to a habitat condition gradient.  We identified fish community metrics within biophysical regions through a multi-step metric elimination process.  We then used structural equation modeling (SEM) to assess our hypotheses about interrelationships between anthropogenic variables and natural landscape gradients at two spatial scales and fish response variables.  SEM allowed us to identify statistically significant relationships between variables and to infer the strongest landscape influences on river biotic integrity.  The linear equations from the models allowed us to predict the integrity status of unsampled river reaches within each region.  We demonstrate how our assessment results can be used to assist with decision making in the context of the National Fish Habitat Action Plan.