Researchers reveal higher historic tortoiseshell trade numbers

By Dana Kobilinsky

Researchers found historical trade of hawksbill tortoiseshell likely killed six times as many sea turtles as previously thought. ©Kyle Van Houtan/NOAA

Historic trade of critically endangered hawksbill sea turtles (Eretmochelys imbricata) may have caused declines nearly six times greater than previously thought, according to new research.

The researchers said the historical global trade patterns that they found also align with current unauthorized fishing activities. “There’s a strong overlap between countries exporting turtles for tortoiseshell and countries today that have high rates of illegal, unreported and unregulated fishing,” said Emily Miller, an assistant research scientist at the Monterey Bay Aquarium and lead author of the recent study published in Science Advances. “It’s likely related to historical economic and political aspects of these trade networks that have developed over time.”

In the study, the team first collected as much historical data on the hawksbill sea turtle trade that they could find. One co-author contributed Japanese customs records of tortoiseshell imports that had never been published before. Other co-authors then pored through all published sources on hawksbills and curated them into a database.

But the researchers ran into a problem because trade records showed only how many kilograms of turtle scutes —the individual plates that make up a turtle’s shell — were reported. “We wanted to know how many turtles were killed to understand the impact on the global population,” Miller said. Material from the scutes is often carved into items including sunglasses, bracelets, guitar picks and combs.

The researchers were able to get stranded and seized turtle specimens to derive relationships to convert the kilos of scutes into the number of turtles actually killed.

They estimated that nearly 9 million turtles were harvested over the 150 years they had recorded. “The previously published estimate was approximately 1.2 million,” she said.

Miller said they came up with a larger number because of the extra data they were able to get their hands on. But previous studies also assumed only the largest individuals were the ones being sold. “Because we were able to get a seized shipment that came into the U.S. in the modern era, we were able to figure out it wasn’t just a few large individuals but many smaller adults, subadult and juveniles,” she said.

Then, the team looked at how patterns of hawksbill trade lined up with illegal and unreported fishing. There was a strong overlap between the countries with high illegal, unreported, and unregulated (IUU) fishing rates and the countries that were historically exporting tortoiseshells, she said. “Poor governance in those areas and long-standing trade networks drive these patterns,” she said.

Miller said this can inform management decisions today. She suggests since there is such overlap, enforcement agencies should train and cross-deputize officers to be able to handle both fishing and wildlife trafficking cases.

Because this is global trade, Miller said it is an international issue and international awareness will help contribute to solutions.

For individuals, she suggests people be aware of what products they are purchasing when they’re vacationing in tropical regions and also paying attention to where their seafood is coming from.

Dana KobilinskyDana Kobilinsky is associate editor at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.

Read more of Dana's articles here.


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