Recovery of critically imperiled taxon like sturgeons (order Acipenseriformes) requires effective conservation actions that address multiple concurrent stressors on population persistence. Geomorphological change to substrate conditions at spawning sites was identified as the most plausible cause where restoration could have a positive effect on recruitment for endangered white sturgeon (Acipenser transmontanus) in the Upper Columbia River, Canada. Here we describe outcomes from a formal process to prioritize sites for spawning habitat restoration that met biological and physical criteria to ensure effectiveness following implementation. Existing substrate conditions were described at multiple spawning locations and the biological (e.g., interstitial space) and physical (e.g., substrate mobility) functionality was assessed using expert opinion and existing literature. Structured decision-making was used to develop restoration alternatives and prioritize one for construction in-river. The leading alternative was built in-river between October 2022 and April 2023 over an area of 5,800 square meters. Substrate material was placed to a depth of two times the largest particles size (i.e., 0.60 m), and the composition of the rock provided a mix of larger material (maximum size = 0.30 m diameter) to provide substrate retention and smaller material (minimum size = 0.10 m) to provide suitable interstitial habitat for sturgeon early life stages. Multiple spawning events were detected in each of the first three years following construction and physical monitoring indicates limited infilling of substrates. While simple in concept, implementation of substrate restoration within large river habitats is a challenging undertaking but represents a positive shift toward habitat-based recovery efforts.
 

Acipenser transmontanus,spawning,habitat restoration,structured decision making