Archaeologists Discover Ancient Canals Used to Trap Fish in Belize 4,000 Years Ago

Roughly 4,000 years ago, hunter-gatherers in Central America built a network of canals and ponds to trap fish. Their system could have captured enough seafood to feed 15,000 people each year, according to a study published this month in the journal Science Advances.

“It’s really interesting to see such large-scale modifications of the landscape so early—it shows people were already building things,” Claire Ebert, an archaeologist at the University of Pittsburgh who was not involved in the research, tells the Associated Press’ Christina Larson.

The fish-trapping network is located in what is now Belize. It spans nearly 16 square miles and is the oldest known system of its kind in Central America.

In 2017, researchers used drones and Google Earth imagery to investigate the system, which is located within the bounds of the Crooked Tree Wildlife Sanctuary in northern Belize. They found 167 excavated trenches and close to 60 ponds, as Science News’ Bruce Bower reports.

Then, in 2019, a drought in the region made it possible for them to excavate the typically waterlogged canals.

The researchers took samples, which they sent off for radiocarbon dating and other analyses. The results suggest the ancient fisheries were built between 2200 and 1900 B.C.E., before the rise of Maya civilization. The system’s age was a surprise, as researchers assumed it had been built by the Maya.

“It never occurred to us that hunter-gatherers around 4,000 years ago might have engaged in this sort of collective, huge construction effort on this scale because nothing like it had ever been found or recorded in Central America before,” says study co-author Eleanor Harrison-Buck, an anthropologist at the University of New Hampshire, to New Scientist’s Becky Ferreira.

The system was built around the same time as a major drought. What was once a perennial wetland became a seasonal marshland, with flood waters receding every spring and summer.

When the wetlands were submerged, freshwater fish and other aquatic creatures would have been able to swim freely throughout the zig-zagging trenches. But when the waters receded, the fish likely became trapped in the ponds, where hunter-gatherers could have easily speared them.

Some archaeologists have suggested that the drought led hunter-gatherers to become increasingly reliant on domesticated plants like maize. But researchers didn’t find any maize pollen in the canals. Instead, they think the hunter-gatherers began relying more on fish-trapping, as well as drought-resistant plants like amaranth.

“For Mesoamerica in general, we tend to regard agricultural production as the engine of civilization, but this study tells us that it wasn’t just agriculture—it was also potential mass harvesting of aquatic species,” says Harrison-Buck in a statement.

Pre-Maya hunter-gatherers may have built the system, but their Maya descendents did eventually start using it around 3,000 years ago. They may have returned year after year for annual fish harvests and social gatherings, which could have eventually morphed into more permanent settlements.

The abundant seafood could have supported a growing and increasingly sedentary population, and such “intensive investments in the landscape” may have helped give rise to the complex Maya civilization, says study co-author Marieka Brouwer Burg, an anthropologist at the University of Vermont, in the statement.

Today, the canals and ponds are mostly full of sediment. But even after 4,000 years, they still work as intended. “Locals inform us that the ponds still concentrate fish during the dry season,” the researchers write.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.