The Vancouver Aquarium says it will bring back beluga whales, ending months of speculation that the sudden deaths of two belugas last year —and resulting public controversy — might have been the end of captive cetaceans at the facility.

In November, the only whales at the Vancouver Aquarium, belugas Aurora, 30, and her calf Qila, 21, died within nine days of one another, after signs of illness but without any clear cause of death.

President and CEO John Nightingale vowed the aquarium would leave "no stone unturned" in its investigation, and would not return belugas to the pool until a cause of death had been determined.

Today, the aquarium revealed there is still no definitive cause of death, but belugas will return — to a new pool, in the Canada's Arctic exhibit which was already slated for construction in the fall.

The exhibit will be open in time for spring break 2019, he said.

Qila, left, and her mother Aurora, back, swim at the aquarium in Vancouver, B.C. in January 2015. (Darryl Dyck/Canadian Press)

No more breeding, ends in 2029

The new beluga exhibit will have a "research-first paradigm," and unlike the previous beluga program, there will be no breeding of the captive animals, said Nightingale.

It also has an end date.

"We intend to discontinue the display of belugas by the end of 2029," which is the end of the aquarium's current lease with the Vancouver Park Board, he said.

The Vancouver Aquarium has been under increasing pressure from animal rights groups and some municipal politicians to end the display of cetaceans. The park board has discussed holding a municipal plebiscite next year to let voters decide whether the facility should be allowed to keep whales, dolphins and porpoises.

The aquarium owns several belugas on loan to other facilities. The new exhibit, which will have three to five belugas, may or may not include those animals, depending on what whales will fit best together in a non-breeding environment, said Nightingale.

He said it is important to continue research on belugas, which are threatened by toxins in the wild and the impacts of climate change on their Arctic environment.

"This institution will continue to be the one and only place in Canada scientists can do research on belugas that are trained to participate," said Nightingale.

He said scientists can study metabolism and other traits in a captive environment that would be difficult or impossible to research on big, fast moving animals in the wild.

The aquarium will also continue its marine mammal rescue program, which includes keeping cetaceans deemed non-releasable by authorities.

Protesters interrupt a Vancouver Park Board meeting on Nov. 28, 2016. (Vancouver Park Board)

No 'smoking gun' in beluga deaths

Since Qila and Aurora died, the aquarium has carried out an "exhaustive" investigation, sending tissue samples to outside laboratories and reviewing operations at the beluga tank.

That work, which has cost more than $100,000, has not yielded "a smoking gun," the aquarium said.

"We have not found a definitive cause of why the animals died," said Dr. Martin Haulena, the aquarium's chief veterinarian.

The investigation is ongoing, with the most likely cause being a toxin that may never be identified, said Haulena.

Foul play has also not been ruled out, he said.

"Whatever happened seems very specific to that exhibit, where the animals were at the time," said Haulena.

The investigation has yielded some risk factors the aquarium can improve on, said Haulena, including security around the exhibit, and limiting runoff from surrounding plants and soil.