Scientists have discovered that baby reef fish possess an internal magnetic compass that helps them find their way home at night.
Publishing their findings in the Current Biology journal, the research team had studied how cardinal fish are able to swim home in total darkness.
“This study is the first clear demonstration that reef fish larvae possess magnetic senses to orient them at night. Up until now, we only knew adult birds, marine mammals, sharks and boney fish have this in-built sense of direction,” said Professor Mike Kingsford, from the ARC Center of Excellence for Coral Reef Studies at James Cook University.
Working with colleagues from Germany, the scientists collected cardinal fish that were less than a centimetre long at One Tree Island on the Great Barrier Reef (GBR). The fish were then tested on their orientation in total darkness using the same magnetic field as the GBR.
Normally, the fish orientated to the southeast. However, when researchers changed the magnetic field clockwise by 120 degrees, all the fish changed the direction they swam in, turning further west instead.
“Our results show that larvae can use their magnetic senses to point them in the right direction when it's night time,” said Professor Kingsford.
After being hatched from eggs, larvae reef fish disperse in the ocean for days or months. Then, they will either return home or find another reef to settle in, and then usually remain there for the rest of their lives.
“The study tells us these baby fish actually have brains. They know where they are going and are strong swimmers. As a result, they have some control over the reef they end up on. It's not just about being led by the currents,” said Professor Kingsford.
More information: www.coralcoe.org.au
Link to the study: www.cell.com/current-biology/fulltext/S0960-9822(16)31279-9