This article was created in partnership with the National Geographic Society.

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.

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.

Here and there they could see the scattering of adult sturgeon expected at this time of year.

And then there was the big one.

River giant

The 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.”

View Images This side-scan sonar image from the Hudson River reveals Atlantic sturgeon in new detail. Photograph by John Madsen, University of Delaware

Arne Ludwig, who is the co-chair of the IUCN Sturgeon Specialist Group and a biologist at the Leibniz Institute for Zoo and Wildlife Research in Berlin, says the status of sturgeon and their paddlefish kin is unchanged, although he pointed to promising reintroduction plans for Atlantic sturgeon, for instance, in some European waters where they were extirpated long ago.

Any recovery in the Hudson and elsewhere along the East Coast will inevitably take time. The Atlantic sturgeon can take a couple of decades to reach spawning age.

Erica Ringewald, a spokeswoman for the New York State Department of Environmental Conservation, said the sighting of the giant fish, along with data from the annual tagging studies and rising counts of juvenile sturgeon, “bolstered the case that New York’s actions to protect this fish more than two decades ago with a moratorium are working.”

She added that the state hoped to expand the sonar scans to the rest of the river.

But independent biologists told me they were far more downbeat, chastened by the scope of losses.

In the Hudson and other American waters, the fishery for Atlantic sturgeon has seen spasmodic waves of depredation, particularly during a caviar craze in the late nineteenth century and then several more times in the 20th century.

Albany beef

This rhythm is easy to track in New York Times stories through that stretch. An August 1881 item used the term of the day, “Albany beef,” to describe heavy demand for sturgeon meat: “In former years the catch of the sturgeon in the Hudson River was amply sufficient to supply all demands for the beef at low prices. Within the past few years, however, the fish have become scarce and shy.”

The result, according to the story? Sturgeon were being imported to New York from as far away as the Kennebec River in Maine and Saint Johns River in Florida.

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A 1927 article reflected another pulse of overfishing with this title: “’Albany beef’ trade wanes as Hudson sturgeon dwindle.”

Adding to the challenge, sturgeon, like shad and striped bass, face a kind of double jeopardy when they leave their spawning rivers and, as adults, cruise the Atlantic Coast. Uneven regulation was a factor.

In my first New York Times story on collapsing Hudson River sturgeon populations, in 1996, commercial fishermen were irate that New Jersey was slow to stop sturgeon harvests.

In the Hudson, the sign of trouble was a sharp drop in the abundance of the youngest fish, which would wander into shad nets every spring (and be released). One shad fisherman, Bob Gabrielson, visibly upset by this, told me how the armor-like knobbly “scutes” along the bodies of the youngest fish, not yet dulled by wear and tear, gleamed like hammered silver. “They’re the most beautiful thing in the world,” Gabrielson said.

The species is listed federally as endangered in the New York region and three others and threatened in the Gulf of Maine.

The discovery of a sturgeon so large in the river I’ve lived along, and reported on, since 1991 deeply excited me. This was particularly the case because, in 2010, I’d been out on the Hudson with Higgs and other state biologists doing the tagging study and videotaped the scene as they hauled a seven-foot, 120-pound male sturgeon onto their 21-foot boat to measure and inspect.

I couldn’t imagine what a 14 footer would be like.

Sustainable management?

To widen the view of this sonar signal, I turned first to John Cronin, an old friend who’s encountered the Hudson and its biological bounty in more ways than anyone I know. His four-decade-plus career along the Hudson has included commercial fishing for shad (a species now greatly depleted from the river), patrolling for pollution as the Hudson Riverkeeper and teaching environmental policy at nearby Pace University.

He sees last summer’s sonar image less as a sign of hope than a reminder of just how profound the near-complete depletion of the Atlantic sturgeon has been—along with the loss of other once-keystone commercial species like the American shad.

The loss is not just of fish but of the relationship communities have with their environment when fisheries are sustainable, Cronin said. He lamented how mismanagement of harvests, even when the science was clear, led to the final crash in the 1990s and then a ban on catches that will persist for many years, if not decades, to come.

In an essay on his Earth Desk blog in 2013, centered on Native American lore around a “sturgeon moon,” Cronin captured the epic scale of the jolt this ancient species has felt in Earth’s Anthropocene age of human impacts.

“Overharvesting of its meat and caviar, pollution, habitat alteration, power plant intakes—the list of insults that humans have invented trump every challenge thrown in the sturgeon’s path during 2,000,000 centuries of life on Earth,” he wrote. “Worth remembering the next time someone passes you the caviar….”

Given the slow maturation and long lives of sturgeon, the losses have been akin to clearcutting an ancient forest, agreed John Waldman, a biology professor at the City University of New York and author of Running Silver: Restoring Atlantic Rivers and their Great Fish Migrations.

What did he think of the sonar view of a fish as big as the biggest Atlantic sturgeon of any age?

“This makes me think we often don’t really know that much about the status of sturgeon in any river,” Waldman said.

He said the biggest sturgeon are big for a reason: “They’re almost totally cryptic and elusive and this is deep and murky water.”

Sturgeon have been known to leap from the water on occasion, he said, “but it’s not like spotting the humpback whale that was in the lower Hudson a few years ago. They surface every few minutes.”

“It’s a marvelous thing to see, even if just that one for now,” Waldman said.