Robot fish developed by British scientists are to be released into the sea off north Spain to detect pollution.

If next year's trial of the first five robotic fish in the northern Spanish port of Gijon is successful, the team hopes they will be used in rivers, lakes and seas across the world.

The carp-shaped robots, costing 20,000 pounds apiece, mimic the movement of real fish and are equipped with chemical sensors to sniff out potentially hazardous pollutants, such as leaks from vessels or underwater pipelines.

They will transmit the information back to shore using Wi-Fi technology.

Unlike earlier robotic fish, which needed remote controls, they will be able to navigate independently without any human interaction.

Rory Doyle, senior research scientist at engineering company BMT Group, which developed the robot fish with researchers at Essex University, said there were good reasons for making a fish-shaped robot, rather than a conventional mini-submarine.

"In using robotic fish we are building on a design created by hundreds of millions of years' worth of evolution which is incredibly energy efficient," he said.

"This efficiency is something we need to ensure that our pollution detection sensors can navigate in the underwater environment for hours on end."

The robot fish will be 1.5 metres long -- roughly the size of a seal.