A specialized boat prowled the waters of Boone Lake last Wednesday, stunning fish with a non-lethal shock.
The electrofishing boat, which transmits an electrical current into the water, is an important tool that biologists use to monitor the health of aquatic life at the reservoir. The boat’s crew plucked immobilized fish from the water with a dip net and transferred them to a metal container at the center of the craft.
Typically, the fish will remain stunned for a couple of seconds, although the duration depends on their size.
“It’s based on surface area, and so typically larger fish are more susceptible to getting hit a little harder,” said Jon Michael Mollish, a fisheries biologist with the Tennessee Valley Authority. “Some fish, you can’t capture them at all. They’ll feel it coming from a mile away.”
With lake levels returning to normal, biologists with the TVA expect there will be a fishing boom at Boone Lake over the next few years.
“The carrying capacity of the lake has increased,” said John Justice, a fisheries biologist, “so when that happens, the fish population usually explodes for a few years. We’ve seen that in other reservoirs.”
Eventually, Justice said, the fish population at Boone Lake will normalize, but for now, the sudden increase in food and other available resources will drive a surge in the fish population, which is good news for avid anglers.
The agency will typically sample the fish population once every three years at other reservoirs. Since the Boone Lake water level dropped, biologists have been coordinating with the Tennessee Wildlife Resources Agency to monitor the health of aquatic life twice a year there.
“We’ve been working with TWRA to basically look at the fish population and document changes from the time the water went down until the water goes back to normal pool,” explained Shannon O’Quinn, a TVA water resource specialist.
So far, biologists have seen no negative shifts in the fish population.
O’Quinn said the agency has also been working with the TWRA to plant low vegetation and concrete structures, called reef balls, on exposed land to create habitats for fish. When the water level returns to normal, that will give fish the nursery areas they need to restore their populations in the reservoir.
When they capture a fish, researchers will typically take its weight and measurements, which gives them an idea of its fitness. Before releasing it, they also look for anomalies such as parasites or lesions.
Mollish said fish occupy different habitats within the reservoir and feed on different types of animals. A catfish will generally feed on just about anything, he said, but the longnose gar may only feed on different types of minnows, shiners and forage fish.
“Understanding the ratio and proportion of your top predators along with your forage fish, along with your suckers, along with your minnows and pulling all those different types of groups together gives you a comprehensive picture of how healthy your reservoirs are,” Mollish said.
Justice said biologists compare the information they gather to a database they’ve maintained for more than 30 years.
“We’re looking at this in terms of trend analysis,” Justice said. “We’re looking for changes over time with the fish community.”
Researchers try to eliminate as many variables as possible, which means sampling at around the same time each year. They will also take note of the temperature.
“It’s very, very cold out here today, so our results may fluctuate as a result of this cold snap that we’re experiencing,” Justice said, sitting at the controls of the boat as it hummed along. “We note those types of anomalies in the data as we’re collecting that.”
Biologists also try to sample a diverse representation of the local habitat.
“We don’t want to go to just the primo habitat out there,” Justice said. “We get a good representation of the good, fair and poor habitats.”