Baby fish ‘steer by the sun’ (Science Alert)

Posted on February 23, 2014 – 05:14 pm

Rich_Carey_Fish_shutterstock Very small fish avoid getting lost in the vast ocean using the Sun as a compass, research has found. Image: Rich Carey/Shutterstock

Baby coral reef fishes find their way home using the sun and a body clock to steer by.

A remarkable discovery by an international team of marine scientists has found that tiny fish, no more than a few millimetres in length, avoid getting lost and eaten in the vast ocean and navigate their way to safety using a ‘sun compass’.

When baby fish hatch from the egg on a reef they are swept away by currents into the open ocean – and an epic struggle begins as these tiny creatures seek their way back to the home reef, or another nearby, where they can settle in safety, explains Professor Mike Kingsford of the ARC Centre of Excellence for Coral Reef Studies and James Cook University.

“Failure to get back to a reef spells death for baby fish, and we’ve known for some time that they use their senses of hearing and smell to locate the reef and head back to it.

“The fact that we’ve shown they also have a sun compass in their tiny heads and can orient themselves according to the sun’s position through the day provides the missing link in their navigational toolkit, ” he says.

The researchers tested their theory using a small plastic swimming pool and baby cardinal fishes at One Tree Island on Australia’s Great Barrier Reef. In a matter of seconds the fry turned and headed in a south southeasterly direction – and kept on heading that way even when the researchers turned their pool.

“The currents that sweep the baby fish off the reef generally set in a north-northwesterly direction, so to get back to it the fish have to swim SSE. The big question was: how did they know where that point of the compass lay, and keep to it?” Prof. Kingsford says.

“Though smaller than a good many insects, baby fish are surprisingly strong swimmers and they can push up against the current for several days, covering distances of twenty kilometres or even more. The mystery was how they maintained a correct orientation during this life-or-death journey.”

However when the researchers ‘clock shifted’ the little fish six hours back in time, they were fooled by the position of the sun and began automatically to swim in an opposite direction – to the NNW. Clock shifting involves putting the fish in a dark room and using artificial lights to reset their body clocks to a time six hours earlier.

Source: www.sciencealert.com.au

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2007-02-25 09:20:30 by Muriatic_acid

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Baby fish 'steer by the sun'  — ScienceAlert
The researchers tested their theory using a small plastic swimming pool and baby cardinal fishes at One Tree Island on Australia's Great Barrier Reef.


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