Underwater GoPro footage has helped provide Kiwi scientists with the first direct evidence that groups of fish communicate to keep safe from predators.
While scientists have known fish send messages to each other for mating purposes or to defend territory, this is the first time research has shown they also use special "contact calls" to keep together.
The team from the University of Auckland's Institute of Marine Science published their findings overnight in the international journal Nature Scientific Reports.
Led by Master's degree student Lucy van Oosterom, the researchers carried out experiments using captive wild bigeyes, a nocturnal, cave-dwelling species found along New Zealand's north-east coast. Bigeyes have a distinctive "pop" call, which has an estimated range of 31.6m. This vocal behaviour, coupled with relatively sensitive hearing organs, led researchers to assume bigeyes communicated in groups - but evidence has been anecdotal, until now.
Using underwater hydrophones, a GoPro camera and an MP3 player, the team played recordings to the fish of their reef environment and another of bigeye vocalisations.