Spawning Activity and Migratory Characteristics of American Shad and Striped Bass in the Cape Fear River, NC

Abstract

SMITH, JOSEPH ALAN. Spawning Activity and Migratory Characteristics of American Shad and Striped Bass in the Cape Fear River, NC. (Under the direction of Joseph E. Hightower)

Anadromous fish populations within the Cape Fear River, NC have experienced declines since the late 1800s. Three low-head lock and dam structures contributed to this decline by limiting access to upstream habitat. I used egg sampling and sonic telemetry to characterize patterns of migration and spawning activity for American shad and striped bass. Plankton samples were taken below each lock and dam, and at two locations farther upstream. Distribution and stage of development of American shad eggs, as well as observed spawning activity, suggest that most American shad spawning took place below the lowermost lock and dam (river km (rkm) 97). Egg density decreased by an estimated 90% for each successive dam moving upstream. In 2007, 20 American shad and 20 striped bass were captured and transported to a release location upstream of the three locks and dams, where they were tagged with sonic transmitters and released. Sixty percent of American shad in 2007 moved 1 to 33 rkm upstream of the release site, at an average migration rate of 2.30 rkm/hr. All 2007 striped bass moved downstream upon release. However, two striped bass made secondary upstream migrations of 52 and 134 rkm, through two and three dams respectively, and at an average rate of 2.58 rkm/hr. In 2008, 20 American shad and 20 striped bass were captured, tagged with sonic transmitters, and released at their capture locations (all but two striped bass downstream of the first lock and dam). Sixty-five percent of American shad and 77% of striped bass made upstream movements past the lowermost lock and dam in 2008, with average migration speeds of 3.2 rkm/hr for American shad and 3.0 rkm/hr for striped bass. Furthermore, 35% of American shad and 25% of striped bass that made upstream movements were able to migrate upstream of the uppermost lock and dam (rkm 186). Combined results suggest that Lock and Dam #1 had the highest egg collections and a tie for the predicted proportion of the American shad run (35%, tied with the upper river), and Lock and Dam #3 had the highest egg collections and highest predicted proportion of the striped bass run. The locking program established for upstream fish passage provides some access to historical spawning habitat, although spawning of American shad is concentrated in areas below the dams. Further improvements in fish passage should benefit both species.