Answer:
This behaviour is known as Mimicry
Step-by-step explanation:
This happens when one fish looks alike the other one and gets benefited due to the resemblance. It often helps them from being eaten and even help them to hide themselves from the predator, making it a anti predator adaptation. There are four types of mimicry, they are aggressive, batesian and Mullerian etc. Here the fish becomes the self-mimicry, as the body part resembles to them and to the predator it looks innocuous to let the prey extra time for its escape.