'Sixth sense' helps fish spot water flows

A "sixth sense" in fish allows them to track changes in water flow left by prey, even without the aid of vision, a research has said.

The findings could help resolve a long-standing mystery about how these aquatic creatures respond to their environment, the researchers noted.

It is well-known that fish respond to changes in their fluid environment. These include avoiding obstacles and reducing swimming effort by slaloming between vortices, or whirlpools.

"We identified a unique layout of flow sensors on the surface of fish that is nearly universal across species, and our research asks why this is so," said Leif Ristroph, assistant professor at New York University.

"The network of these sensors is like a 'hydrodynamic antenna' that allows them to retrieve signals about the flow of water and use this information in different behaviours," Ristroph added.

To explore how fish exploit flow information, the research focused on a fish's "lateral line" - a system of sensory organs known to detect both movement and vibration in the water that surrounds them.

They particularity considered the line's sensory-laden canals that open to the environment through a series of pores.

Just as the shape of a TV or radio antenna is designed to detect electromagnetic signals, the fish's canal system is like an antenna laid out on the body surface and configured to be sensitive to pressure changes, the researchers noted.

The study appeared in the journal Physical Review Letters.