Fish cough.

Much like any of us when we’re feeling under the weather, and despite their vastly different respiratory systems, fish cough — though they don’t cough because they’re feeling ill. Instead, fish rely on this technique to expel unwanted matter such as debris or mucus from their gills.

When dust, sand, or other particles get lodged in a fish’s airways, they contract their buccal and opercular cavities to create intense negative pressure. This, in turn, reverses water flow through the gills, forcing out any irritants caught inside. It’s otherwise called a “gill purge,” and it removes obstructions from the airways.