Researchers zap zombie bass

2014-04-07 16:12
Fishing. (File photo, AP)

Fishing. (File photo, AP)

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Rogersville - Bernie Fuller has fished for decades, yet he's never witnessed anything to match the sight of dozens of zombie bass eerily rising out of a north Alabama lake.

Americans like Fuller spend about $48bn annually fishing for fun, and they like knowing what's in the water with their bait. To provide answers to that question and more, biologists are conducting a study where they use "electrofishing" to stun fish in Tennessee Valley Authority lakes.

Momentarily incapacitated by a weak electrical charge that's fed into the water from a boat equipped with a humming generator, fish large and small floated motionless to the surface during an electrofishing trip last week. They were scooped up with a net and placed into an aerated holding tank.

Eyes wide and mouths agape, stunned fish were measured, weighed and checked for illnesses and parasites. Within a few minutes the animals snapped out of a zombie-like state, and workers put them back in the water to swim away.

Fuller was among nine area anglers who went along on a TVA research trip last week on Wheeler Lake near Rogersville, and he grinned as one big fish after another floated to the top in a reservoir where he thought there were far fewer and much smaller bass based on his fishing experience.

"I've learned there's a lot of fish in here," Fuller said after a day on the water.

John Justice, a fisheries biologist with TVA, said fish rarely suffer any lasting effects from electrofishing.

"Generally speaking they recover within a few seconds to a couple of minutes," he said.

Justice said data collected during successive years of electrofishing provides biologists with valuable information about how to best manage the lakes, which are some of the most biologically diverse in North America. The statistics show whether adjustments need to be made to things including water flow, catch limits, stocking programs and water levels, he said.

Stunned fish

"By looking at the overall health and condition of the fish we collect we can tell a lot about what's going on with the fishery," said Justice.

Protection groups including People for the Ethical Treatment of Animals contend fish feel pain, but electrofishing has become a standard tool for biologists. Justice said a slight shock is much easier on fish and other wildlife than the previous practice of dousing a sealed-off cove with a chemical compound called rotenone, which killed fish so they could be scooped out and counted.

Electrofishing is simple enough. A boat is equipped with a pair of fiberglass arms that support a metal pole that hangs off the bow over the water. Three metal cables hang from the pole into the water, and an insulated wire connects the cables to an electrical generator in the rear of the boat.

With the current flowing and cables in the lake, an operator steps on a foot pedal to electrify the water with a 6-amp charge that extends outward and downward as much as 2.5m. Fish within the field are stunned and float to the surface, along with the occasional turtle or snake.

Once in a tank on board the boat, stunned fish appear lifeless as they float atop the water. Most recover within moments, and some are actively flipping and jumping by the time they are measured.

Of about 200 bass and crappie collected during three hours of electrofishing at Wheeler Lake, every fish went back into the water alive once researchers were done.

"They look real healthy," Morris said.

Fishing doesn't always mean catching, but Fuller said seeing how many fish gather around fallen trees and rocks taught him a lesson about where to concentrate while on the water.

"I think it will help me be a better fisherman," he said. "A much more patient fisherman, anyway, for sure."

Read more on:    us  |  marine life  |  conservation

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