Here’s a video of a fish fighting with its mouth, but not with its teeth. The Sarcastic Fringehead is a 10-inch fish that lives on the bottom of the ocean around California’s Channel Islands. Most of the fighting is an act of intimidation, but sometimes they make contact. In what’s perhaps another illustration of evolution, some of the the action includes a walking motion using the fish’s pectoral fins.
Source: YouTube/Channel Islands Marine Sanctuary