How can crappie hover motionless in mid-water for hours?

The swim bladder — a gas-filled buoyancy organ the fish fine-tunes until it weighs exactly nothing in the water. Neutral buoyancy means hovering costs almost no energy, and that is the foundation of the whole crappie lifestyle: hang suspended at the depth where plankton and minnows concentrate, spend nothing, and sip whatever passes overhead. It is also why schools show up on sonar as clean mid-column clouds, and why matching their exact depth matters so much — the fish have no reason to leave the layer they are balanced in.

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