Atlantic sturgeon have no shortage of adjectives that suit them. Ancient, as in a fish species that has been around so long it swam with dinosaurs. Giant, as in the largest fish native to the Chesapeake Bay - it can grow to 14 feet and weigh 800 pounds. Long-lived, as it can survive up to 60 years.

And potentially one more: federally endangered.

The National Marine Fisheries Service, a part of the National Oceanic and Atmospheric Administration, in October proposed listing most Atlantic sturgeon populations along the East Coast as endangered species, including those native to the Chesapeake, because they could become extinct in the foreseeable future.

Its recommendation came in response to a petition filed by the Natural Resources Defense Council that argued that current protections, including a coastwide ban on harvest, had been inadequate because they failed to address a gauntlet of other problems such as sturgeon bycatch in other fisheries, impacts of pollution, ship strikes, dredging and global warming.

The NMFS is expected to make a final decision about the listing late next year.

The recommendation is a mixed bag, scientists say.

It could bring more protection from ship strikes and sturgeon bycatch in other fisheries. It could also mean more support for research in the James River, where a small breeding population remains.

But scientists fear it could doom hopes to eventually stock sturgeon in Maryland tributaries, where the giant fish is thought to be extirpated from all rivers. A 15-year old sturgeon tagging program in Maryland may also be in jeopardy.

"Certainly, listing increases public awareness of the plight of the species," said Brian Richardson, a fisheries biologist with the Maryland Department of Natural Resources. "But it most likely is going to have a huge impact on our sturgeon restoration projects and our strategies."

Sturgeon are an anadromous species, meaning they spawn in freshwater portions of rivers but spend most of their lives migrating along the coast before returning to spawn in their river of origin. They were once abundant in large rivers along the East Coast, including those in the Bay. Capt. John Smith proclaimed that the James River "had more sturgeon than could be devoured by dog and man."

But sturgeon were heavily fished for both their meat and eggs in the mid to late 1800s, decimating the population. The biology of Atlantic sturgeon made it difficult for them to rebound. Females do not reach sexual maturity until they are 15 or more years old. Also, they produce only moderate numbers of eggs compared with other species, and do not reach maximum egg production until late in life.

The NMFS determined that Atlantic sturgeon populations all along the East Coast were imperiled. It subdivided the entire coast into five "distinct population segments" and recommended that all be listed as endangered under the federal Endangered Species Act, except the Gulf of Maine population, which it recommended listing as threatened.

The entire Chesapeake Bay was identified as a distinct population segment, but within the Bay, Atlantic sturgeon are only known to spawn in the James River, although some spawning in the York River is suspected.

Sturgeon are easily caught in a variety of fishing gear and the NMFS said that bycatch in both federal and state waters was a "significant threat" to Bay sturgeon numbers, as even small rates of mortality could harm the remnant populations.

The potential impact on fisheries in the Bay would not be known until a final listing decision is made. But the proposal said that recent actions taken by Virginia to reduce sea turtle interactions with pound nets and prohibit staked or anchored gill nets - which are a particular problem for sturgeon - in portions of the James and Rappahannock rivers would likely reduce the chance that Atlantic sturgeon will be caught in the gear. Maryland also prohibits the use of anchored gill nets.

The proposal noted that the NMFS fisheries managers had not taken any specific actions to reduce the bycatch of Atlantic sturgeon in fisheries that take place in federal waters, such as those targeting dogfish and monkfish, and called existing bycatch reduction measures "inadequate for reducing bycatch of Atlantic sturgeon in federally regulated fisheries."

Any listing may also bring more protection against strikes by commercial ships. Sturgeon often spawn in large rivers - which also support large ports - making them vulnerable to ship strikes, especially in narrow passages. More than two dozen were reported killed in the James from 2005 through 2008.

Greg Garman, director of the Virginia Commonwealth University's Center for Environmental Studies, said a single container ship is believed to have killed five adult sturgeon as it squeezed through a narrow, shallow section of the James River this fall.

"That is something that is really a concern for us, and I think the endangered species listing will force the vessel operators to pay attention," he said.

Richardson said some sturgeon have also been reported killed by ships in the vicinity of the Chesapeake and Delaware Canal, which connects the Chesapeake and Delaware bays.

Sturgeon are particularly sensitive to the Bay's water quality problems because they require relatively high levels of dissolved oxygen and are bottom feeders - a bad combination as oxygen concentrations are lowest in deep waters of the Bay. If cleanup efforts improve water quality, the amount of available sturgeon habitat in the Bay would increase by about 13 percent a year, NMFS said.

Warming temperatures may exacerbate the habitat problem in the future. "Nutrient loading and eutrophication of the Chesapeake Bay is expected to get worse with temperature changes and other effects associated with climate change," the NMFS said.

The loss of clean, hard substrates where sturgeon eggs attach during spawning is another important habitat limitation.

Scientists expressed surprise that the fish was recommended for listing as endangered, rather than threatened. An endangered species is one that could become extinct in the foreseeable future, whereas a threatened species is one that could become endangered in the future.

Endangered status - if granted in the final decision expected next year - is likely to bring more restrictions on researchers than a listing as threatened. The "take" of any endangered species, which can include killing, harassing and even handling, is strictly regulated, even if it is done by researchers.

"We were all very surprised by the proposed endangered listing," Garman said. "There is no panic about it, but there certainly is concern in the research community that it will be harder to work toward restoring the species."

Because the NMFS estimates that the James River has fewer than 300 spawning adults in a given year, researchers may only be permitted to handle a few fish each year.

In recent years, a coordinated effort has been under way to capture, tag and track sturgeon in the river in the hope of identifying important habitat areas, such as spawning grounds.

That work can be fatal to the fish, Garman acknowledged. "We occasionally lose fish," he said. "We work very hard not to, but it happens to all of us, particularly if we are working with warm water temperatures."

For more than a decade, the U.S. Fish and Wildlife Service and Maryland Department of Natural Resources have conducted a reward program that pays watermen to hold captured sturgeon in Maryland until they can be tagged and released.

"We didn't think there were any sturgeon here when we started that reward program in 1996," said Steve Minkkinen, head of the USF&WS Maryland Fisheries Resource Office. "Now we have encountered over 2,000. That's quite a few when you didn't think you had any."

Information gleaned from the sturgeon catches was used by the EPA to help craft water quality standards for the Chesapeake. Most of the captured fish were from the James and Hudson rivers. None were from Maryland.

The reward program would likely be a casualty of an endangered listing, scientists said, because catching and holding a sturgeon until it is tagged would almost certainly be defined as a "taking."

"If it goes endangered, our reward program is going to be done," Richardson said.

Also at risk would be the Maryland program that has captured and reared sturgeon in anticipation of spawning and stocking sturgeon in state rivers in the future.

Generally, the NMFS has frowned on hatchery-based stocking as a restoration technique. But without a stocking program, sturgeon will not return until fish from the James or York River stray into Maryland waters and begin spawning on their own. With the reduced populations in those rivers, that's not likely to happen for decades.

"I don't see them coming back in my lifetime without a hatchery-based restoration," Richardson said.

Richardson said the state would make no decision about whether to continue its program, or what to do with the fish it currently holds, until after a final decision is made next fall.

Dave Secor, a fisheries scientist with the University of Maryland Center for Environmental Science, has researched sturgeon in the Bay and along the East Coast. He said the Atlantic States Marine Fisheries Commission, a state-federal commission that regulates migratory fish stocks, had successfully coordinated sturgeon research over the past decade. That work is often conducted by agencies and researchers working on shoestring budgets, and Secor said the NMFS should try to keep that framework intact.

Unlike striped bass, sturgeon "is not a money fish" for state agencies, Secor noted. If the NMFS regulations make it too difficult, the researchers, who mostly study sturgeon because it is an ancient and interesting species, "could get dissuaded."

Such research has made significant findings. For example, it was only discovered in recent years that the James River continues to have a spawning population of sturgeon, and there is some evidence it may be increasing.

"I'm kind of optimistic," Secor said. "I'm just pleased that we have sturgeon to talk about in the Chesapeake. Ten to 15 years ago, I couldn't imagine having this conversation. We were much more pessimistic about their status."

NOAA is accepting comments on the proposed listing through Jan. 4.