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Researchers find hope for return of Carolina sturgeon

By Hannah Miller

For the last several decades, most North Carolinians have been denied what was once a common sight: an Atlantic sturgeon leaping for the sky as it made its way to and from its spawning grounds high up inland rivers.

The large, ocean-going fish – a throwback to dinosaur days – was overfished to the point of near-extinction as its tasty roe supplied caviar factories along the coast in the 18th and 19th centuries.

For those that survived, the way to much of their freshwater spawning area, the rocky fall line where the Piedmont meets the Coastal Plain, became blocked by dams.

Their numbers dwindled. Catching them became illegal in 1998, and they went on the endangered list last year.

“People would encounter them occasionally,” said Joseph Hightower, U.S. Geological Survey biologist and N.C. State biology professor who is leading a sturgeon study.

Those who did remembered. “They just don’t look like anything else,” Hightower said.

“These hard structures along the sides, bony plates, give them an armored look,” said Joe Smith, research technician on the project.

They take prodigious leaps for no apparent reason. Smith once “saw the entire fish come out of the water. It was the coolest thing I had seen in a long, long time.”

On the way back?

Recent studies, sparked by a sturgeon’s fortuitous leap on the Roanoke River in 2009 and capped by scientists’ recovery of 39 fertilized eggs there this year, may indicate the beginning of a comeback.

Hightower theorizes that the breathing space provided by the 1998 fishing moratorium has allowed a new generation of the slow-maturing fish to reach reproductive age: 10 to 12 years for females, 5 years for males. The bottom-feeding fish, which subsist on marine worms and snails, can live to 60 years.

On the Roanoke, where no dams block the way, the fish have been congregating the last several years at the fall line near Weldon.

It’s considered one of the species’ traditional spawning grounds. Sturgeons seem to prefer dropping their eggs in the cracks among rocks, where predators can’t get the quarter-inch-long fry so easily.

That 2009 leap reported by a fisherman startled scientists because it came in the fall of the year – not the spring, when common knowledge said sturgeons spawned.

Boatloads of cooperating researchers from N.C. State University, the N.C. Wildlife Resources Commission and the N.C. Division of Marine Fisheries subsequently converged on the area. They attached acoustic tags to several fish and set receivers at riverside to track sturgeons’ comings and goings.

When repeated receiver “beeps” showed fish congregating just below the falls, Hightower and his NCSU researchers started submerging egg mats improvised from circular floor-sanding pads, hoping eggs would drift down and stick on the filaments.

“It’s a needle in a haystack,” he admitted. The 32 pads were each the size of a large pizza; the river at that point is more than 100 yards wide.

In 2012, they recovered one egg, which was hatched in a tank at N.C. State. The fry was released in the Roanoke when it was about 3/4-inch in length and is now “probably in Albemarle Sound, if it didn’t get scarfed up,” Hightower said.

This year’s 39 black-brown eggs, all but two of them fertilized, are in test tubes at NCSU after being recovered during one week in September.

At 2.5 mm in diameter, they’re scarcely bigger than the head of a pin, and Smith said it’s hard to believe such a big fish “can start that small.”

The 39 are only a fraction of the hundreds of thousands of eggs that were out there, the scientists believe, since one female can carry more than 1 million eggs.

Another surprise was the high water temperature at the time of discovery: 75 degrees Fahrenheit. But for a fish releasing eggs in fall, choosing the season’s warmest days makes sense, Hightower said.

“You don’t want to be a little tiny fry looking for something to eat heading into the wintertime,” he theorized.

A learning experience

“What we’re trying to do is learn as much as we can about conditions for spawning – temperatures, flow, water depth, substrate …,” he said. The goal is to apply the knowledge to other rivers where sturgeon might be encouraged to spawn.

A separate study is discovering both adult and juvenile sturgeon in the lower reaches of Cape Fear River, though none apparently have reached the traditional spawning area near Erwin, in Harnett County.

For years, three low dams that impound much of southeastern North Carolina’s water supply – at Riegelwood, Elizabethtown and Fayetteville – have blocked the fish’s way.

But last year, the Riegelwood dam was transformed into a $13 million rapids as the Army Corps of Engineers, working with the state, stacked massive boulders on its downstream side. Shad and striped bass have been jumping it to spawn, but so far, no sturgeon.

Overall success of that rapids, to be determined at the end of a study next year, will guide discussions of transforming the other two dams. “We’re optimistic passage will be good this spring,” said Frank Yelverton, a Corps biologist.

“There’s not a pot of money out there to do anything,” he said. But when success at Riegelwood’s Lock and Dam No. 1 is proven, “Hopefully there’ll be moves to obtain money to do No. 2 and No. 3 also.”

He wasn’t too disappointed at the lack of sturgeon so far. “They’re rare,” he pointed out. And, “They don’t spawn every year.”

A sturgeon recovery would have implications for the state’s economy, Hightower said. “To the point that commercial fishermen could catch them and provide caviar, that would be a very valuable fishery,” he said. “But that’s a long way out.”

In the meantime, he said, “As biologists, you want to figure out what’s limiting a fish that’s gotten to the level of being listed as endangered. … See if there’s a way to turn it around.”

What’s being learned on the Roanoke, he said, “is a first step toward that.”

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