The fish known for being able to change its gender is the clownfish. Clownfish, which are often recognized from the movie "Finding Nemo," exhibit a fascinating social structure within their anemone homes. In a group of clownfish, which usually consists of a dominant female, a dominant male, and several smaller males, the female is the largest and most dominant. If the female dies, the dominant male can undergo a sex change and become the new female. This adaptation allows the group to maintain reproductive functionality despite changes in their social structure.