Washington D.C. [USA] Apr, 20 : A recent study claimed that fish releases certain chemicals called, 'disturbance cues,' into the water to warn others such as predators, about the danger.
The study was published in the Journal of Animal Ecology.
"Disturbance cues may help to explain why some fish populations crash after they decline past a certain point," said Kevin Bairos-Novak, one of the researchers.
While researchers have been aware that fish release chemicals into the water for 30 years, this is the first time their use has been studied.
Fish signaled most when in the presence of familiar fish, but signaled far less or not at all when in the presence of strangers, or when on their own.
The signals provoked a 'fright response' in fish they knew, including freezing, dashing about and then shoaling tightly together. Fish uses this behaviour to defend themselves against predators.
"When minnows were present alongside familiar minnows, they were much more likely to produce signals that initiated close grouping of nearby fish, a strategy used to avoid being eaten by predators," said Bairos-Novak, one of the researchers.
Disturbance cues are voluntarily released by prey after being chased, startled or stressed by predators.
One of the main constituents of the signal is urea, found in fish urine.
Fathead minnows, caught at a lake, were placed in groups with familiar fish, unfamiliar fish or as isolated individuals.
The research team then simulated a predator chase. The fish responded by shoaling, freezing and dashing when they received a signal from a group they knew. But they did not take significant defensive action when receiving cues from unfamiliar fish or isolated minnows.
Disturbance cues are voluntarily released by prey after being chased, startled or stressed by predators.
"It is exciting to discover a new signaling pathway in animals. We found that fish are able to manipulate the behaviour of other individuals nearby by issuing a signal," said Maud Ferrari, Supervisor.