The Georgia Aquarium, stymied in its quest to bring 18 wild-caught beluga whales into the U.S., has given up the fight.

The aquarium announced Tuesday it would not appeal the most recent court decision blocking the import.

“Although we firmly disagree with the Judge’s ruling, after much consideration we have chosen not to appeal the decision,” the aquarium said in a statement. “Extending the appeal process would only add to an already lengthy series of legal proceedings, and we believe our decision is in the best interest of the beluga whales residing in Russia.”

The aquarium applied for a permit to import the belugas in 2012. The National Oceanic and Atmospheric Administration denied the permit, writing that such an action could spur more international trade in the endangered ocean mammals.

Suing to have the decision reversed, the aquarium argued that the decision was “arbitrary and capricious.” That lawsuit was denied in September by U.S. District Court Judge Amy Totenberg.

Since 2005, the aquarium has invested millions in a beluga conservation program, conducting population studies, funding research and visiting the Sea of Okhotsk, where the 18 prospective whales originated.

The whales were caught between 2006 and 2011 off the northeast Russian coast. They are being held at the Utrish Marine Mammal Research Station in Russia.

Three belugas have died at the Atlanta aquarium in the past three years. The latest, the adult female Maris, who was one of the first animals in the aquarium’s collection when it opened 10 years ago, died suddenly Oct. 22. The cause of that death is still undetermined.

Maris had two successful pregnancies, but both infants died shortly after birth, one in 2012 and the other earlier this year.

The aquarium currently has two young belugas in its collection, Grayson and Qinu.

Aquarium officials said that the small number of belugas in captivity in the United States represents a lack of genetic diversity, which imperils any breeding program. They were hoping to expand that diversity by importing the 18 wild-caught whales.