Fishes have an ability to communicate with each other to swam closer together, when they want to escape from dangerous predators.
In a study, researchers worked on Bigeyes (Pempheris adspersa) – a fish that is active at night. Researchers used a special kind of sound that is commonly used by Bigeyes, and was considered as a type of contact call to remain in group. (These types of contact calls have also been found in many other vertebrates such as marine mammals.)
Initially, it was thought that in order to remain in group, visual cues along with hydrodynamic cues are used by fishes. So, researchers worked on the Bigeyes, exposed them to “recordings of ambient reef sound at higher sound levels”, and found that fishes started coming in group. This gathering is thought to protect fishes from predators. It has also been observed that on listening to sound recordings, the Bigeyes also increased their own calling rates to increase contact with each other.
This research is the first direct evidence to show that fishes remain in contact for protection purposes. Previously, it was known that fishes send messages to each other to defend territory and for mating purposes.
van Oosterom, L., Montgomery, J., Jeffs, A., & Radford, C. (2016). Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species Scientific Reports, 6 DOI: 10.1038/srep19098