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Baby reef fish have internal compasses

AAP logoAAP 21/12/2016

Baby reef fish have an internal magnetic compass that points them to home at night, Queensland researchers have discovered.

Tiny Cardinal fish, the size of a fingernail, are able to swim towards a certain direction without sunlight or stars to guide them, the James Cook University study found.

Even in total darkness they swam towards the southeast and then changed direction when the magnetic field was altered, the research revealed.

It is the first demonstration that larvae have magnetic senses, according to JCU coral expert Mike Kingsford.

"Up until now, we only knew adult birds, marine mammals, sharks and bony fish have this in-built sense of direction," he said.

Reef fish hatch from eggs into a larval form and disperse for days or months in the ocean before returning home or finding another reef to settle on. Once they get to a reef, they generally stay there for a lifetime.

Sample hatchlings less than one centimetre long were collected from One Tree Island on the Great Barrier Reef for the research.

"The study tells us these baby fish actually have brains. They know where they are going and are strong swimmers," Professor Kingsford said.

"As a result, they have some control over the reef they end up on. It's not just about being led by the currents."

It is hoped that the study will help develop more accurate knowledge of where larvae go and in maintaining sustainable fish stocks.

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