Distribution of Fishes in the Vicinity of Dredging Operations in the James River, Virginia

Potential effects of dredging-induced underwater noise, suspended sediment plumes, and hydraulic entrainment have been identified as sources of concern for protection of fishery resources. Although such concerns have persisted for decades, conclusive evidence either substantiating or refuting them is lacking. One means of establishing the likelihood of actual impacts to fishery resources is examining the distribution of fishes in relation to the conduct of the dredging project. In the present study, fisheries hydroacoustic techniques were used to examine abundances and spatial and temporal distribution patterns of fishes around a hydraulic cutterhead dredging operation in a tidal reach of the James River, Virginia in October 1999. Hydroacoustic surveys were conducted during various stages of the tide on two spatial scales: several kilometers up and downstream of the dredge, and within several hundred meters of the dredge site or pipeline discharge area. Surveys were completed during periods of active dredging as well as when the dredge was idle. Gill nets were deployed to characterize the local fish assemblage and to identify acoustic targets. White perch (Morone americana), spot (Leiostomus xanthurus), and gizzard shad (Dorosoma cepedianum) accounted for almost half of all fish captures. Estimates of fish density with distance (30 m increments) from the dredge were examined for evidence of fish attraction to, or avoidance of, an operating dredge.