Dozens of fish rise out of the lake like zombies. Their eyes and mouths are wide open.

What brought them to the surface? A boat is moving through the water. It has a machine that generates electricity. When it sends an electric shock through wires hanging in the water, fish near the boat are stunned. They float to the surface. Workers scoop them up with a net. They put them into a tank of water in the boat.

The workers are biologists, scientists who study living things. The biologists are electrofishing—for answers, that is.

Studying the fish will answer questions. Does the lake have enough water flow? Should there be limits on how many fish people catch? How big are the fish? Are they healthy? And by the way, are there any fish that don’t belong there—invasive species?

The biologists don’t keep the fish. In a short time the fish snap out of their zombie-like state. Workers put them back into the water.

“Thank you for your answers, fish. You may swim away now.”