A pair of Atlantic sturgeon. (Courtesy of National Oceanic and Atmospheric Administration)


Andrew Revkin reports in National GeographicCOLD SPRING, NEW YORK One day last June, two researchers were towing a special sonar system up and down the Hudson River near Hyde Park, New York, the site of President Franklin Delano Roosevelt’s home, when they saw something pleasantly shocking.They were helping state biologists assess whether the spawning or foraging of a fabled and endangered bottom-feeding denizen, the Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus), was being disrupted when commercial vessels dropped anchor in a spot designated as a waiting area to manage ship traffic.The anchorage, established in 1999, happened to be located in a stretch of the Hudson that is one of the most important spawning grounds in its range along the coast from Florida through Canada’s maritime provinces. More anchorages were planned elsewhere in the Hudson.Not receiving our free updates? Unlike a simple depth sounder, this “side-scan” sonar sweeps high-frequency beams of sound out at angles, producing a detailed three-dimensional portrait of the river bed and any decent-size fish—and often precise enough to reveal the sturgeon’s distinctive profile, as low-slung as a Formula One car.John A. Madsen, the University of Delaware geologist running the sonar, recalled the screen was showing the expected mix of bottom features—areas where currents had sculpted “sand waves,” scrapes and furrows in the anchorage.River giantThe sonar revealed a sturgeon roughly twice as long as anything seen that day—confidently estimated at just over 14 feet from nose to tail tip. That’s a size that, even decades ago, even a century ago, was considered a rarity. But now, it was unimaginable given what this species had endured.“When I first saw it, I said, ‘You’ve got to be kidding me,’” Madsen recalled. But there was no mistaking the image. He and his colleague, Dewayne A. Fox of Delaware State University, have extensively used this sonar system in sturgeon habitat elsewhere along the Atlantic Coast and in the Republic of Georgia, home to half a dozen species of sturgeon, all deeply endangered, including Huso huso, which can reach lengths of 18 feet and is the source of Beluga caviar.Amanda Higgs, a state biologist who’s been tagging and netting Hudson sturgeon for more than a decade, was out on the water working nearby that day. As news of the sighting spread, she had a reaction echoing a famed scene in the movie Jaws.“Our boat is way too small to deal with a fish like that,” she said in an email.Biologists estimate a sturgeon that length could easily weigh 800 pounds.One exciting aspect of knowing the Hudson has female sturgeon that large is that bigger females produce vastly more eggs than smaller ones—up to 8 million at the high end. “Size matters,” said Jane Lubchenco, a marine ecologist at Oregon State and a former administrator of the National Oceanic and Atmospheric Administration.The debate over adding anchorages along the Hudson is on hold for now after fierce opposition from environmental groups and scientists, including a cautionary 2016 letter to the Coast Guard from Madsen and Fox, who’ve been doing surveys around Hyde Park for several years.But any harm from dragging anchors would be just one of a host of far broader assaults on this species, and sturgeon worldwide, over the last century.

“The most threatened group of animals”

In 2010, the International Union for Conservation of Nature was blunt in its warning: “Eighty five percent of sturgeon, one of the oldest families of fishes in existence, valued around the world for their precious roe, are at risk of extinction, making them the most threatened group of animals on the IUCN Red List of Threatened Species.”