Although fishwheels have been used for more than 10 years by scientists to research salmon migration up rivers in Alaska and the Pacific Northwest, the Roanoke River project represents the first time one has been used for that purpose in the eastern United States.
"It seemed to me that if it worked well for salmon, it should work for anadromous fishes here," Hightower explained. Anadromous fishes are species that spend most of their lives in the ocean, but return to freshwater rivers to reproduce.
The project is important because scientists want to know more about anadromous fish populations in the Roanoke and other North Carolina rivers. The results including the timing and extent of the fishes' migration will help state regulators set catch limits for each species. Hightower hopes to use the fishwheel approach on other North Carolina rivers as well, especially the Neuse and Cape Fear rivers.
Hightower is also interested in finding out whether a relationship exists between migration and river flow, since hydropower dams on the Roanoke and other rivers may affect fish migrations by changing natural river flow patterns.
For the first time this year, Hightower and his colleagues are using a second technique to track fish in the middle of the river channel, where they aren't being caught in the fishwheel. Slightly downstream from the wheel, the researchers have set up a "hydro-acoustic" sampling device, which emits eight "pings" per second and then records the echoes created by individual fish. A fish shows up as a line of dots on a computer screen; software then allows the researchers to determine the size of the fish being tracked.
"The combination of these two approaches is giving us a lot of information about what's going on in the river," Hightower said.
So far this year, the run of blueback herring has been especially strong 3,400 altogether, which is greater than th
Contact: Dr. Joe Hightower
North Carolina State University