8 Dec 2025

Assessing Fish-Passage Rates

Abstract: Riverine fragmentation by dams, culverts, and other barriers has led to the precipitous decline of migratory fishes nationwide. Accordingly, fish-passage restoration has emerged as a significant issue for resource agencies, restoration professionals, and fisheries managers. This special report addresses the key scientific challenge of measuring fish-passage rates before and after restoration. A variety of techniques for both forecasting (preproject) and monitoring (postproject) fish-passage rates are reviewed. A set of guiding questions are presented to help practitioners select a method appropriate to their site, resources, and time line. Four case studies are then presented to demonstrate a subset of these methods in practice: fish community movement through floodgate structures in Missouri, movement patterns through river restoration structures in Colorado, fish movement around a low-head weir in Mississippi, and watershed-wide passability estimation using professional judgment in Nevada. These projects represent a range of conditions and are intended to provide practitioners with real-world examples to use as models for their own studies.