When fish are born in coral reefs, they are often tiny and poor swimmers. Because of this, they are pushed away from the corals from which they are born weeks before they learn to swim effectively. Remarkably, 60% of these fish manage to make it back to their first homes despite their unfavorable beginnings. Historically, scientists believed fish used the sun to navigate back to their birthplaces. However, it is understood they could navigate at night just as effectively. Researchers set out to find out how. Their findings? The fish are magnetic.

Sun, Magnetic, Or Both?

In this particular case, researchers used the larvae of Doederlein’s Cardinalfish, which can reach lengths up to only five inches. This species can be found near One Tree Island, located off the coast of Australia, where scientists collected their specimens. When these fish hatch, the currents carry them in a north-northwest direction. Experiments show that they invariably swim south-southeast, guided by the sun, to the coral in which they hatched. To confirm the magnetic theory, scientists tested the fish with a device that both creates a uniform magnetic field and allows for direction manipulation. With the larvae in a tank surrounded by the magnetic device, the scientists turned the Earth’s normal magnetic north 120 degrees clockwise. To prove the theory correct, the fish swam right along with the magnetic change. The lead author of the study’s publication, Gabriele Gerlach, suspects that other marine life “have the same behavior -- they hatch and then are washed out into the ocean for days, weeks, even months. And they might have this same magnetic orientation behavior.” Fish aren't the only creatures with a magnetic sense—magnetism also affects sharks, moths, and even humans! Interested in learning more about ways magnetic forces are at play in nature? Visit our blog page for more articles like this one.