Most electric-type pokemon generate their own electricity, but Chinchou are unable to do so. Instead, they most absorb electricity from their surroundings, swimming after thunderstorms until they are struck by lightning, and feeding on other pokemon who are killed by their own weakness and the fact that water conducts electricity.
A thunderstorm is a feast for any Chinchou, but one too infrequent, unreliable, and seasonal to allow them enough food to survive. Although their evolved form of Lanturn can hunt by luring pokemon to their lights, Chinchou lights lack the brightness to draw water pokemon their way, and they are fragile enough that such a hunting method would be extremely dangerous for the hunter. Therefore, when too long has passed without one, Chinchou gather to create a thunderstorm of their own, discharging enough electricity into the water to kill all but the strongest fish within a one-mile radius. As a hunting method, it is complete overkill; the small Chinchou can not possibly consume that much food, and instead it creates an ample meal for scavengers like Pelipper.
"Chinchou" has therefore entered the language as an adjective to describe anything where the benefits of an activity are far outweighed by the destruction it caused. For instance, slash-and-burn agriculture is also called Chinchou agriculture, and like the Chinchou who move across the ocean, farmers who burn forests rotate from forest to forest, allowing them time to rebuild before burning again. The same can not be said, however, of the many "Chinchou factories" in cities like Celadon, where weak environmental protections allow factories to flood rivers with waste, killing water-types as surely as a Chinchou school's thunderbolts. For these factories, Chinchou themselves are among the victims, and the water remains poisonous for years if not generations.