Researchers recorded crampfish calls capturing this noise as one chased a smaller fish. These popping sounds functioned as an () aggression signal. When the/a [confish] has been chased and wishes to submit, it [cheek]s its head in a submissive gesture and produces [quicking] noises like these. 

The researchers compared the aggressive and submissive calls and found that the sound posed in a submissive signal were shorter and more high-pitched. Unlike many animals that use sounds to drive/draw in potential mates, crampfish appear to use their calls only as a [lib] of social status. When a little fish makes submissive sounds to a larger one, neither has to invest in a physical confrontation, which is good news for small [fry], like Nimo.