This is important work. It isn’t just that fish can communicate, it’s how they communicate. There is a whole system present to transmit an emotion from one fish to another fish who then processes that emotion, (presumably) experiences their own, then behaves according the experience the other fish is having. The whole process is underpinned by neurological and chemical interactions that are comparable to other animals including humans. Understanding how that process works helps us understand animal life as a whole, including ourselves.