Effectiveness of a Rock Arch Rapids for Fish Passage at a Lock and Dam on a Large Coastal River

Three lock and dams (LD) on the Cape Fear River, North Carolina, maintain water levels for municipalities and industry but impede migratory fishes to varying degrees.  To improve fish passage, a rock arch rapids fishway was constructed in 2012 at LD-1 (river kilometer (rkm) 97).  This is the first implementation of this design for anadromous fishes and along the Atlantic coast.  We evaluated fish passage through the LD-1 fishway and via locking procedures at LD-2 (rkm 149) and LD-3 (rkm 186) in 2013 and 2014 using sonic-tagged striped bass Morone saxatilis, American shad Alosa sapidissima, and flathead catfish Pylodictis olivaris.  In 2013, 21% of striped bass (n=43), 50% of American shad (n=32) and 80% of flathead catfish (n=20) passed through the LD-1 fishway.  Mean duration downstream of LD-1 prior to passage ranged from 4.1 days for striped bass to 18.4 days for American shad.  Passage via locking procedures ranged from 36% for American shad at LD-2 (n=9) to 100% at LD-3 for striped bass (n=7) and American shad (n=5).  The fishway passed each species in 2013, but did not meet pre-determined success criteria (80%) for anadromous species.  Design modifications may be explored to improve passage at this or future sites.