Distribution of Spawning Activity by Migratory Fishes in the Neuse River, North Carolina, After Removal of a Low-Head Dam.

Abstract

In 1998, the Quaker Neck Dam was removed from the Neuse River near Goldsboro, North Carolina, restoring access to more than 120 km of potential spawning habitat for migratory fishes. The goal of my study was to examine the distribution of spawning activity of anadromous and migratory riverine fishes above and below the former dam site. During February-May 2003 and March-May 2004, I sampled plankton at nine locations on the upper Neuse River and five locations on tributaries. I also conducted standardized electrofishing to assess the relative abundance of fishes and estimate run timing of anadromous species. Evidence of spawning activity was detected upstream of the former dam site for three anadromous species (American shad Alosa sapidissima, hickory shad A. mediocris, and striped bass Morone saxatilis) and several riverine migratory species including gizzard shad Dorosoma cepedianum and one or more redhorse species Moxostoma spp. Eggs of American shad, hickory shad, and striped bass were staged and used to estimate mortality rates. Ages and mortality rates were used along with water velocity to estimate locations of spawning activity. Instream flows, which are regulated by an upstream dam, were substantially higher in 2003 than 2004. This appeared to affect the locations of spawning activity for all three anadromous species. A greater proportion of American shad eggs (92.7%) and larvae (96.4%) in 2003 were collected upstream of the former dam site, compared to percentages for eggs (70.2%) and larvae (50.0%) collected in 2004. Hickory shad generally spawned in downstream reaches of the river and were the only anadromous fish in the study to show significant use of the tributaries. Sites upstream of the former dam site accounted for 28.8% of the hickory shad eggs and 67.4% of the hickory shad larvae in 2003 and 12.2% of hickory shad eggs and 56.0% of larvae in 2004. Substantially more striped bass eggs (77.2%) and larvae (77.8%) were collected upstream of the former dam site in 2003, compared to the percentages of eggs (18.9%) and larvae (0.0%) in 2004. These results demonstrate that anadromous fishes will take advantage of upper basin spawning habitat restored through dam removal as long as adequate instream flows are present to facilitate upstream migration.