Environmental flow management seeks to balance human water use with the ecological needs of riverine systems, yet predictive tools are often limited to a subset of well-studied or economically important species. Trait-based approaches offer a mechanistic and transferable framework for anticipating fish assemblage responses to hydrologic alteration by linking flow regimes to functional characteristics shared across species. We present a holistic, multi-trait framework that integrates existing trait databases and synthesized flow–ecology relationships to predict fish species and assemblage responses to altered flow conditions.
Trait information for North American freshwater fishes was compiled from established databases and supplemented using phylogenetic surrogacy. Published flow–ecology relationships were translated into directional flow–trait linkages and applied across a broad suite of hydrologic metrics to estimate relative risk for individual species within local assemblages. Rather than isolating single traits or life history strategies, this approach incorporates a wide range of trophic, life history, habitat, and tolerance traits to better capture the multifaceted nature of ecological response to flow alteration.
The framework was evaluated using contrasting case studies representing short-term natural disturbance and long-term anthropogenic hydrologic modification. Predicted responses more closely aligned with observed assemblage changes under anthropogenic alteration, while responses to natural climatic events were more variable, highlighting differences in predictability related to magnitude and duration of flow change.
By emphasizing trait integration over taxonomic specificity, this approach supports environmental flow decision-making in data-limited systems and enables extrapolation to unstudied species. The results underscore the value of holistic, trait-based tools for assessing community-level vulnerability and informing adaptive environmental flow management.