Some Like It Slow: A Bioenergetic Evaluation of Habitat Quality for Juvenile Chinook Salmon in the Lemhi River, Idaho

Management and conservation of freshwater habitat requires fine spatial resolution and watershed-scale and life-stage-specific methods due to complex linkages among land, climate, water uses, and aquatic organism necessities. In this study, we present a valley-scale microhabitat resolution, process-based bioenergetics approach that combines high-resolution topobathymetric LiDAR survey with two-dimensional hydrodynamic and bioenergetics modeling. We applied the model to investigate the role of lateral habitat, stream morphological complexity, water use, and temperature regimes on aquatic habitat quality distribution of juvenile Chinook salmon (Oncorhynchus tshawytscha) within the Lemhi River (eastern Idaho, USA). Modeling results showed two key aspects: (i) a reduction in diverted flows is not sufficient to improve habitat quality potentially because of a legacy of morphological simplification (directly due to straightening and wood removal and indirectly due to low in-channel flows) and (ii) morphological complexity and connectivity with side channels and margin areas, which are key and vital elements to support suitable habitats that meet or exceed energetic needs to sustain or promote growth of individuals and populations.