Evaluation of Culverts for River Herring Passage in the Albemarle Sound Watershed of North Carolina

Despite a moratorium on take, population abundances of river herring in North Carolina remain a small percentage of historic values, and are considered depleted by the NC Division of Marine Fisheries. Among the multiple stressors impacting river herring are habitat loss and barriers to migration. Road culverts may impede upstream migration, resulting in an effective loss of spawning habitat. Although ideal culvert design for river herring passage is currently not well understood, culverts are known to impede migration by increasing flow velocity beyond maximum swimming speeds of fish. Using publically available data, we identified 17 culverts in the Albemarle Sound watershed that are potential barriers to river herring migration. By modeling the culvert hydraulics across a range of expected stream discharges using the FishXing software, we were able to predict factors that impede passage for each culvert. Of the 17 culverts identified, 8 were predicted to impede migration under feasible flow conditions. Predictions will be verified by sampling below and above culverts during the 2014 spring migration. Results of this study will benefit the NC Division of Marine Fisheries by enabling managers to advise and prioritize culvert construction and replacement projects in order to aid this historically important fishery.