A roadmap for aquatic organism passage assessments of stream crossings

ABSTRACT Road crossings can fragment streams, limiting fish growth, survival, and fitness. Yet, millions of road stream crossings remain unassessed for fish passage. Here, we summarize the results of road crossing assessments using the National Aquatic Connectivity Collaborative’s Road Crossing Aquatic Organism Passage Assessment and explain the lessons learned while implementing assessments for the first time. We believe these insights can help guide conservation organizations who are beginning the daunting task of assessing road stream crossings. To assess road crossings in eastern South Dakota, our objectives were to (1) create a mobile decision-­support tool for planning and coordinating road crossing assessments, (2) assess road crossings for aquatic organism passage, (3) expand assessment capacity through interagency collaboration and training, and (4) prioritize barriers for remediation. We designed an ArcGIS Field Map to create a mobile application that allowed partners to locate, prioritize, and conduct assessments. We assessed 528 road–stream crossings, of which 38% (n = 142) were considered at least minor barriers to stream fishes. Culverts were the most common structures associated with fragmentation. Interagency collaboration and training workshops were invaluable for increasing survey capacity and engaging partners. We prioritized barriers for mitigation using the National Aquatic Barrier Inventory and Prioritization Tool and selected three barriers for removal. We identified three lessons learned: (1) prioritizing and planning crossing assessments is essential for efficient barrier inventories, (2) field efficiency is improved by integrating mapping, data collection, and visualization into smart phone applications, and (3) interdisciplinary collaboration and training enhanced the capacity of organizations to assess and manage aquatic connectivity. The release of user-friendly decision-support tools, including the National Aquatic Barrier Inventory and Prioritization Tool and the National Fish Passage Coordination Map, can assist aquatic resource managers in implementing assessments and promote interagency collaboration to improve connectivity in fragmented riverscapes.