Evaluating Methods to Establish Habitat Suitability Criteria: A Case Study in the Upper Delaware River Basin, USA

Understanding the habitat needs, or habitat suitability criteria (HSC), of aquatic biota is a key component to environmental flow science.  Defining HSC can be challenging because habitat requirements vary by life stage, season, and drainage basin and can be confounded by multiple interacting environmental variables.  HSC can be developed through numerous methods (e.g. expert opinion, field and laboratory studies, literature reviews); however, few studies have evaluated the consistency of HSC developed by different methodologies.  We directly compared HSC developed by the Delphi method (expert opinion) and by primary literature meta-analysis to assess whether these independent methods produce analogous criteria for multiple species (rainbow trout, brown trout, American shad, shallow fast guild) and life stages.  We also calculated available habitat within the Upper Delaware River with each HSC using the Riverine Environmental Flow Decision Support System (REFDSS), a management tool designed to evaluate competing flow management scenarios in the Upper Delaware River basin.  We evaluated the flow management scenarios under each HSC and evaluated the spatial locations of differences in habitat between HSC at multiple scales.  The differences found in this study lend insight into how different methodologies can shape HSC and their consequences for predicted habitat and water management decisions.