Do fish have complex social groups?

Yes, fish do exhibit complex social behaviors. According to Lydia Denworth, during her research on animal friendships, she noted that fish display responses in their brain during social interactions that are somewhat similar to those seen in humans, albeit in a much simplified form. For instance, zebrafish have been observed to freeze when they encounter unfamiliar fish, and they relax when they sense they are with familiar fish. This indicates that fish, like many other animals, are capable of recognizing and differentiating between familiar and unfamiliar individuals in their social groups, reflecting a form of complex social interaction 1.