Fish habitat modelling in large rivers: combining expert opinion and hydrodynamic modelling to inform river management

Abstract

Physical habitat models represent a widely used tool in river management, yet, there is a growing consensus—particularly for large rivers—that fundamental principles have limits, and it is evident that improved methodologies for assessment and design are needed. Here, we suggest a framework that takes steps towards resolving some of these issues, using changes of fish habitat in a large, regulated river as a case study. First, we propose using hydrodynamic modelling in combination with a fuzzy rule-based classification as a tool to delineate and quantify meso-scale fish habitat. Variability in spatial and temporal extent of mesohabitats can be modelled across a range of flows and under non-wadable conditions when standard mesohabitat surveys become largely unfeasible. Second, research effort and empirical data on habitat use and preference of fishes is typically focused on a small group of species and limited for many imperilled or elusive taxa; we suggest using expert knowledge to expand beyond one or a few species to build the biological models for a community-level assessment until empirical data becomes available. Third, sources of uncertainty that are linked to both fundamental elements of habitat models, namely the biological and hydrodynamic components, need to be quantified and reported in modelling outcomes. The steps described in our modelling framework represent key tools for river managers charged with developing environmental flows guidelines in large, regulated rivers.

Keywords:

• Conservation ecology
• uncertainty analysis
• environmental flows
• MesoCASiMiR
• riverine fish
• expert elicitation

Acknowledgements

We would like to thank Mark Gautreau, Colin DeCoste, Craig Wall and several summer students for help during arduous fieldwork, as well as Natalie Rideout for help in editing figures. Furthermore, we would like to thank the fish biologists that provided their expert opinion in this study: Rick Cunjak, Michelle Gray, Mark Gautreau, Kathryn Collett, Gordon Yamazaki, Samuel Andrews, Kurt Samways, Brian Jessop, Bruce Beaton, Gayle Zydlewski, Joseph Zydlewski, John Kocik and Ernie Atkinson.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research project is a part of the Mactaquac Aquatic Ecosystem Study (MAES) funded by New Brunswick Power and NSERC’s Collaborative Research and Development programme (CRDPJ: 462708-13). Bernhard Wegscheider was funded in part by the Dr. William S. Lewis Doctoral Fellowships stipend. The article was greatly improved by comments on earlier versions by three anonymous referees.