Back in April, in the chilly Pacific somewhere off the coast of California, a group of National Oceanic and Atmospheric Administration (NOAA) scientists released a dinner plate-sized juvenile loggerhead turtle named Coco into the water.

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Image: Ralph Pace

Just a few weeks earlier, the turtle was rescued by the US Coast Guard and brought to the Aquarium of the Pacific near Los Angeles for medical care. Once the veterinarians there determined that the animal was healthy enough to be released, researchers took advantage of the situation and attached a small GPS transmitter to its shell. To account for the turtle's growing body, they used stretchy neoprene to do it, so the tag won't get lost as the turtle grows.

For many years, nobody knew where young sea turtles spent their childhoods. North Pacific loggerheads are known to nest on Japanese beaches. They then reappear more than 9,500 kilometres away along Mexico's Baja California peninsula to feed as adults. How they get from Japan to Mexico – during their so-called "lost years" – nobody knows. But in 2014, NOAA researchers conducting a marine mammal survey discovered a large concentration of what seemed to be juvenile loggerheads (Caretta caretta) about 250 miles off southern California. Over the course of several days, they saw at least 70 individuals, which appeared to be juveniles based on their size. 

It's not unheard of (though it is still rare) to see loggerheads in the warm waters off southern California, in an area called the Southern California Bight. When the water heats up, the turtles swim north from their Mexican feeding grounds in search of red crabs, one of their favourite snacks. But the turtles the researchers saw were younger, and they seemed to be swimming south, not north. Had the NOAA team found some turtles en route from Japan to Mexico?

Now that tracking technology has become small enough to be suitable for the young turtles, researchers are finally in a position to shed more light on these mysterious sea turtle migrations. In the process, the information they collect by tracking Coco's movements will also help protect the species, which is classified as endangered by the IUCN.

In the Southern California Bight, loggerheads are threatened by the swordfish fishery. When the waters become warm enough to attract tasty red crabs – and therefore the loggerheads – fishers are prohibited from casting their nets, at least within the Pacific Loggerhead Conservation Area. In 2014, for example, the swordfish fishery there was closed between during that time.

But with better knowledge of how loggerheads use the habitat, fisheries managers might be able to fine-tune the rules to allow turtles and fishers to better coexist. Perhaps turtles and swordfish use different parts of the habitat or use the habitat at different times? That sort of information could allow fishers to continue making a living while also providing the turtles with much-needed protection. 

Coco is the first juvenile loggerhead turtle ever tracked in the Southern California Bight. In the month following its release, the turtle swam through more than 770 kilometres of Pacific Ocean. It's now somewhere off the coast of Baja California – and you can follow Coco's movements at

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The small GPS transmitter was attached with stretchy neoprene to accommodate the turtle's future growth. Image: Ralph Pace
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Image: Ralph Pace
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Loggerheads are classified as endangered by the IUCN and scientists hope Coco will provide crucial info that can be used to better protect the species. Image: Ralph Pace
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Coco is the first juvenile loggerhead turtle ever tracked in the Southern California Bight. Image: Ralph Pace

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