Lolita, a captive orca that has spent more than four decades in an aquarium tank, will be granted the same endangered species protection as her wild relatives, US officials said Wednesday.

Advocates hope the ruling will lead to her release from the Miami Seaquarium, but the matter of Lolita's care remains at the center of an impassioned legal dispute.

She was captured as a juvenile from the waters off the western US state of Washington in 1970, along with six other calves that were sent to marine parks around the country.

The now 7,000-pound (3,200 kilogram) Lolita is the only one of that group still alive. She is believed to be the oldest captive orca in the United States.

Her wild relatives, known as the Southern Resident killer whales, were given endangered species protection by the US government a decade ago.

There are only 78 individuals left in the Pacific Ocean off the northwestern United States and Canada, said Will Stelle, regional administrator of the National Oceanic and Atmospheric Agency (NOAA) Fisheries West Coast region.

Their protected status, from 2005, did not however apply to all orcas in US waters or those in captivity.

Animal rights groups petitioned NOAA to revise the endangered listing and to remove the exclusion of captive whales from the description.

"We find that Lolita's captive status, in and of itself, does not preclude her listing under the ESA (Endangered Species Act)," NOAA said.

"Accordingly, we are removing the exclusion for captive whales in the regulatory language describing the Southern Resident killer whale DPS (distinct population segment)."

- Aquarium life -

The 20-foot (six-meter) orca lives in a 35-foot wide and 20-foot deep tank at the Miami Seaquarium.

Orcas can live as long as 50 to 100 years, according to NOAA.

The decision does not force any change to her captivity, or to the conditions in which she is held, a matter which is overseen by a division of the US Department of Agriculture.

The NOAA rule takes effect in 90 days. Beyond that, making decisions regarding what is best for her "is a very complicated task" that NOAA has not considered and may not become involved with unless formally asked, Stelle said.

The Miami Seaquarium said there are no plans to move her.

"Lolita is healthy, and thriving in her home where she shares her habitat with Pacific white-sided dolphins," said Andrew Hertz, general manager at Miami Seaquarium.

"There is no scientific evidence that the 49 year-old post-reproductive Lolita could survive in a sea pen or the open waters of the Pacific Northwest and we are not willing to treat her life as an experiment."

- Animal rights -

Animal rights advocates are pressing a lawsuit to gain her release.

"Today's proposed rule makes the possibility of Lolita's retirement to a seaside sanctuary tangible," said the Animal Legal Defense Fund.

"Were she to be released, she would be able to live her life with dignity, in an environment that more closely resembles her natural environment. There's even a possibility she could be reunited with her family!"

People for the Ethical Treatment of Animals said it will continue to push for Lolita to be retired from performing and transferred to a seaside sanctuary in her home waters off Washington's San Juan Islands, or even back to her own family pod if possible, since it is believed that her 86-year-old mother is still alive.

"This orca has been trapped for decades in the tiniest orca tank in North America and, for the past 10 years, deprived of the protection from harm and harassment offered by the Endangered Species Act," said general counsel to PETA Jeffrey Kerr.

But Stelle said her survival -- as well as protection of the remaining orcas in the wild -- is not as simple as opening the gates and letting her go free.

"As for Lolita, imagine if you had been in captivity, in a tightly managed environment, fed by humans for the last 40-45 years. Are you ready to be released out into the wild and fend for yourself? And is that going to be successful? Or is that going to be highly unsuccessful?

"Jumping to any particular conclusions about the release -- or not releasing Lolita -- at this stage is very, very premature."