Evaluation of Fish Passage at a Nature‐Like Rock Ramp Fishway on a Large Coastal River

Abstract

AbstractNature‐like fishways are engineered to be low maintenance, aesthetically pleasing, and able to pass a diversity of species. However, evaluations of nature‐like fishways are limited, especially on large rivers and for anadromous species. Therefore, we studied a nature‐like “rock arch rapids” rock ramp fishway constructed in 2012 at the most downstream of three locks and dams (LDs) on the Cape Fear River, North Carolina. We evaluated upstream fish passage effectiveness and time until passage through the LD‐1 (river kilometer [rkm] 97) fishway and via locking procedures at LD‐2 (rkm 149) and LD‐3 (rkm 186) from March to early July for three consecutive years, 2013–2015. We used stationary acoustic telemetry receivers to evaluate tagged anadromous American Shad Alosa sapidissima and Striped Bass Morone saxatilis and introduced potamodromous Flathead Catfish Pylodictis olivaris. For American Shad, raw upstream passage efficiency at the LD‐1 fishway was similar to that for LD passage via locking procedures in this and previous studies (53–65%), but passage rates were considerably lower for Striped Bass (19–25%). Duration downstream prior to upstream passage averaged 14.7 d for American Shad (SD = 10.2) and 11.6 d for Striped Bass (SD = 17.1). The raw upstream passage efficiency of Flathead Catfish at LD‐1 was variable (13–80%), and certain individuals passed multiple times in a season and spent extended durations downstream prior to passage (mean = 17.4 d; SD = 20.8), potentially foraging. The rock arch rapids LD‐1 fishway passed each species upstream in all years, but anadromous fish passage was delayed for some individuals and the fishway did not meet predetermined success criteria (80% passage efficiency), indicating that design modifications may be necessary to improve overall effectiveness.