Policed fish

Fish signal their intentions, for instance, to attack, by means of colour changes and marks. A study recently found that honesty in signalling of intent is encouraged through a group activity in a species of fish.

In Princess of Burundi chichlids – a family of fish that includes damselfish and superperches – a single black streak that was dynamically controlled is seen on the faces of both male and female fishes. The presence of this streak suggests aggressive behaviour towards other fishes. When this streak was falsely put in by modifying the fish, the researchers found that the fish showing false signals were attacked more than the control group. This suggests that the fish have a “social policing” method to weed out false signals.