Scientists observe electric eels hunting in groups

In the Brazilian Amazon, eels exhibit a unique hunting behavior. They gather in groups in a lake along the Iriri River, rising to the surface to breathe. During dawn and dusk, they swim in circles to herd small fish into a tight ball. Then, a few eels break off to shock the fish, making them easy prey. This behavior is rare among fish and resembles that of dogs and killer whales.

What was the environment like in the lake where the eels were observed?

Describe the process by which eels corral their prey.