Evaluating methods to establish habitat suitability criteria: A case study in the Upper Delaware River Basin, USA

Background/Question/Methods

Defining habitat suitability criteria (HSC) of aquatic biota is a key component to environmental flow science.  HSC can be developed through numerous methods; 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 evaluated three alternative flow management scenarios in the Upper Delaware River incorporating each HSC into the Riverine Environmental Flow Decision Support System (REFDSS).  

Results/Conclusions

In general, literature-derived HSC fell within the range of the Delphi HSC, with highest literature support for velocity habitat.  HSC defined based on the interquartile range of literature values and the Delphi method both favored the same flow management scenario; however, HSC defined based on the entire literature range resulted in no favored flow management scenario.  Habitat area predicted using the Delphi HSC fell between the habitat area predicted using the two literature-derived HSC, both at the basin and the site scale.  Predicted habitat increased in shallow habitat areas (stream margins, flood plain) using literature-derived HSC while Delphi-derived HSC predicted increased channel habitat.   The differences found in this study lend insight into how different methodologies can shape HSC and their consequences for predicted habitat in ecological flow modelling and water management decisions.