Effects of a Low‐Head Dam on the Distribution and Characteristics of Spawning Habitat Used by Striped Bass and American Shad

Striped bass Morone saxatilis and American shad Alosa sapidissima in the Neuse River, North Carolina, historically migrated up to 435 km upriver to spawn. However, migration was impeded in 1952 by the construction of Quaker Neck Dam at river kilometer 225 (measured from the point where the Neuse River enters Pamlico Sound). To determine the fraction of tagged fish that migrated upstream of this low‐head dam and the characteristics of selected spawning habitat, we implanted sonic transmitters in 25 striped bass and 25 American shad during 1996 and 1997. We determined preferred depth, water velocity, and substrate composition by measuring those characteristics at both randomly selected sites and sites where spawning was observed. Of 13 striped bass and 8 American shad with transmitters that migrated to the base of Quaker Neck Dam, only 3 striped bass passed the structure, indicating that the dam was an impediment to migration. Striped bass spawning was observed only in the area directly below (within 1.5 km of) Quaker Neck Dam. Although none of the telemetered American shad passed Quaker Neck Dam, American shad spawning was observed from the base of the dam to 1.5 km downstream as well as 3 km above the dam. Striped bass spawned at sites with significantly higher water velocity and significantly larger substrate than on average was found at randomly sampled locations. American shad spawned at sites that were significantly shallower and had significantly larger substrate than was found in random samples. The type of spawning habitat selected by both species is more abundant above than below Quaker Neck Dam, indicating that improved access to upstream reaches would benefit both species.