In a significant setback for the Georgia Aquarium, which has invested more than $2 million in beluga research, the federal government announced Tuesday it has denied the aquarium’s request for a permit to import 18 beluga whales captured in Russian seas.

“The ongoing live capture trade since 1989 has contributed to the decline” of the beluga population and the population in the Sea of Okhotsk appears to be declining, said Michael Payne, chief of the permits and conservation division in the protective resources office of the National Oceanic and Atmospheric Administration.

Speaking in a conference call to reporters on Tuesday afternoon, Payne said because the beluga population in that location could be declining, the permit application doesn’t meet the criteria of the Marine Mammal Protection Act.

He added that the importation of the whales, caught by Russian traders some time between 2006 and 2011 and held at the Utrish Marine Mammal Research Station on Russia’s Black Sea Coast, would probably serve to expand the trade in wild-caught beluga whales.

In a statement, the Georgia Aquarium deplored the ruling, saying, “The decision places the long-term global sustainability of an entire species in limbo.”

The Georgia Aquarium intended to bring the whales into the country to improve the genetic diversity of the captive population and ensure its survival. The whales would have been housed at six different facilities, including the Atlanta facility.

Four belugas who lived at Georgia Aquarium have died, one of them, Nico, while in the care of Sea World in San Antonio. Nico and his colleague Gasper were both rescued from an amusement park in Mexico and brought to Atlanta in poor health. Gasper died in 2007. Marina, a female beluga, died that same year.

A baby beluga died last May. It had been in critical condition since birth.

For five years, the Georgia Aquarium has sponsored scientific research into beluga populations in the Sea of Okhotsk, which lies on the Russia’s east coast, between Sakhalin Island and the Kamchatka Peninsula.

Payne acknowledged that the majority of reliable information about this beluga population has been generated by Georgia Aquarium’s efforts. He added, however, that NOAA’s models, using the Georgia Aquarium research, indicate a more robust population 20 years ago.

“There are a lot of gaps,” he said.

William Hurley, the aquarium’s chief zoological officer and senior vice president, said no “crystal ball” can accurately assess the population from two decades earlier, and that NOAA is using “newly minted concepts” to defend its position.

Asked by a reporter what would happen to the belugas that are currently being held at Utrish, Payne said, “We do not control the live capture operations in Russia. Presumably they will be sold to meet the demands world-wide. But we cannot control the outcome.”

Animal rights activists, who have protested the aquarium’s plan to add belugas to the captive population in the U.S., celebrated the decision. “Great day,” tweeted Hardy Jones of BlueVoice.org. “They got it right thanks to massive public input.”

The statement from NOAA also concluded that five of the whales captured in Russia were 1.5 years old at the time of capture and were “potentially still nursing and not yet independent.” Hurley responded that “the estimate of their ages based on their size and behavior tell us that this is not an issue.”

The Georgia Aquarium has a few options to seek a change in the decision, including an appeal in U.S. District Court and a lawsuit. Said Hurley, “The Georgia Aquarium has demonstrated that it appreciates its relationship with the agency. Litigation is our last option. But it is an option.”