Assessing upstream fish passage connectivity with network analysis.

摘要: Hydrologic connectivity is critical to the structure, function, and dynamic process of river ecosystems. Dams, road crossings, water diversions impact by altering flow regimes, behavioral cues, local geomorphology, nutrient cycling. This longitudinal fragmentation ecosystems also increases genetic reproductive isolation aquatic biota such as migratory fishes. The cumulative effects on fish passage many structures along a are often substantial, even when individual barriers have negligible impact. Habitat can be improved through dam removal or other means improvement (e.g., ladders, bypasses, culvert improvement). Environmental managers require techniques for comparing alternative restoration actions at multiple locations. Herein, we examined graph-theoretic algorithm assessing upstream habitat investigate both basic applied problems. First, used hypothetical watershed configurations assess general alterations with changes in network topology linear vs. highly dendritic) quantity, location, passability each barrier. Our modeling indicates that locations dams limited efficiency near outlet create strong signal but not individually sufficient disconnect system. Furthermore, there exists threshold number beyond which declines precipitously, regardless configuration. Watersheds branched shown less susceptible disconnection measured this metric. Second, model prioritize barrier mainstem Truckee River, Nevada, USA. River application demonstrates ability address conditions common projects including incomplete data, parameter uncertainty, rapid application. study utility approach dendritic networks assuming full basin utilization given species, guild, community concern.