Angling is the most popular way to catch fish, but when DNR’s Wildlife Conservation Section studies fish communities or the biology of rare species, a hook and line isn’t the preferred method.
The most common method is backpack or boat shocking, where fish are temporarily stunned with an electrical charge and then netted. But often scientists want to minimize the stress on fish when they are targeting rare species. This is where kick-seining, traps and other modified nets come into play.
Fyke net wings and entrance (top left) with net-covered rings leading into square trap (center).
Fyke nets are a modified trap that works similar to the weirs native Americans used for fishing. Fyke nets combine netting bags mounted on rigid supports and anchored to the stream bottom with a trap fixed at the end. Net “wings” block the channel and funnel fish toward the entrance of the bags.
Fyke nets are crucial in studies of sicklefin redhorse. In spring, this rare sucker from the Tennessee River basin swims upstream from the lower Hiwassee River to spawn in smaller streams such as Georgia’s Brasstown Creek. En route they meet DNR’s fyke nets, swimming along the wings into the trap. Staff remove and identify captured fish every 12 hours, recording their length, weight, sex and condition.
Implanting a PIT tag in a Robust Redhorse. Photo credit: Alan Cressler
Healthy fish are marked with a Passive Integrated Transponder, or PIT, tag, which has a microchip with a unique electronic signature – similar to microchips implanted in pets. The microchip is activated when it passes near an antenna installed along the stream bottom. The signal goes to a receiver, which records the time and the tag’s identity. Analyzing the data provides details on the sicklefin’s spawning habits.
Fyke nets are also helping DNR and its conservation partners study the robust redhorse. This is another rare sucker but one found in mainstem, Atlantic-slope rivers. Fyke nets and seines are being used to research this fish’s movements in the Savannah River. While data similar to the sicklefin project is gathered, the fyke net in the Savannah study is not left in the river overnight. Instead, it is set below spawning robust redhorse and project staff herd them into the trap using seines.
Each fish is given a PIT tag, but 20 are also implanted with another type of acoustic transmitter. These transmitters send out “pings” that can be detected by arrays of receivers in place throughout the river. The devices will last 10 years, allowing scientists to learn vital details about the long-lived suckers.
Like the fyke? It’s hard not to considering how key these nets are to studying and conserving rare fishes.