Fish ears reveal lot about their private lives

Scientists at the University of Southampton in Britain have found a way to pry into the private lives of fish simply by looking into their ears.

By studying ear stones in fish, which act as tiny data recorders, scientists can now reveal migration patterns and even provide insights into their sex life.

Tiny ear stones called 'otoliths', which are in all bony fishes, store chemical elements picked up from the surrounding water.

"These otoliths can now be used like the Rosetta Stone -- allowing us to read the story of fish migrations from the chemistry of their ears," said co-author Clive Trueman and associate professor in Marine Ecology at the University of Southampton.

"We also found that sex can interfere with the chemical signals. This complicates the job of translation, but provides us with new information about the biology, and private lives, of fish at sea," Trueman noted.

The new insights, published in Methods in Ecology and Evolution, can now be used to better understand movements of fishes throughout oceans and will help in science-based conservation and sustainable fisheries.

As fishes migrate, changes in the water chemistry are recorded in the otoliths, but it is difficult to translate these signals into records of fish movements.

Now researchers have created a translation dictionary - revealing what the different chemical elements stored in the chemical makeup of the stones can tell us about the environments fish have covered.

The research involved raising plaice in an aquarium for one year while measuring the chemistry of the water and the fishes' blood.

At the end of the experiment, they compared the water, blood and otolith chemistry to better understand how elements become integrated into the growing otolith.