Scientist Uses 19th Century "Fishwheel" Device To Study Fish Populations

"One of the things that attracted me to this approach was, unlike gill nets and trawls, it doesn’t hurt the fish," said Hightower, NC State associate professor of zoology and assistant leader of the N.C. Cooperative Fish and Wildlife Research Unit. "The beauty of this project is that the fish are in good shape. We get the information we need and then release them unharmed."

Set on a 38-foot-long platform that floats along the bank of the Roanoke River near Scotland Neck, the machine requires no motor or electrical power supply. The river current turns the wheel, dipping a series of 10-foot-square nets into the water. Fish scooped up by the nets are dropped into a water-filled box, from which Hightower’s research assistants count, measure and release the fish.

The project runs from mid-February to mid-June, and involves counting striped bass, alewife, hickory shad, blueback herring and American shad. The largest catches of striped bass may come in early to mid-May.

The first documented use of fishwheels was from the early 1800s, when they were used to capture shad in East Coast rivers, most notably the Roanoke and Pee Dee rivers in the Carolinas. They were reportedly common along the East Coast as early as 1829.

Since the late 1800s, fishwheels have been used extensively in the Pacific Northwest to catch salmon as they moved upstream to spawn. The wheels were later used by commercial fishery operations on both coasts, but were so successful in catching large numbers of fish that they were banned in most places. They’re still used to harvest fish in Alaska, mostly by native Americans.

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 the 215 blueback and 1,087 total fish caught in 2000. Hightower isn’t sure about the reason for the dramatic increase in the number of blueback herring, but sees it as an encouraging sign. The population of American shad in the Roanoke River, however, appears to be quite low.

Meanwhile, results indicate that striped bass -- which were severely depleted 20 years ago -- are at their highest numbers since scientists first started keeping records, thanks possibly to catch limits and other fishing regulations. "If we do this research over the next five to 10 years, we can tell how well those efforts are paying off," Hightower said.

The Roanoke River fish population research was funded by the U.S. Geological Survey, the U.S. Fish and Wildlife Services, the N.C. Wildlife Resources Commission, and Dominion Generation (formerly Virginia Power). More information about Hightower’s research, including the fishwheel, is on the Web at http://www4.ncsu.edu/unity/users/j/jhncsu/public/jhightower.html.