One of two beluga whales that the Vancouver Aquarium keeps in Stanley Park has passed away.

According to a blog post at the nonprofit’s website, the animal, named Qila, was born at the aquarium in 1995, making it 21 years old.

The post does not state a cause of death or an exact date for the whale’s passing.

Last July, the Vancouver Sun reported that the two beluga whales were “showing key signs of stress”.

Troubling findings presented in that article are similar to the results of an in-depth investigation the Georgia Straight published in February 2014.

The aquarium’s November 16 blog post states Qila was under the care of veterinarians.

“Our marine mammal care team, led by Dr. Martin Haulena and Brian Sheehan, have cared for Qila over the past 21 years,” it reads in part. “There have been days when they’ve spent more time with our beluga whales than they have with their own children, and we are grateful for their incredible leadership, professionalism and care for our marine mammals. Today we’re turning our attention to beluga whale Aurora as she adjusts to the change.”

Qila is the fourth cetacean associated with the Vancouver Aquarium to die within the last two years.

In July of 2015, a beluga whale whose father is owned by the Vancouver Aquarium died at a SeaWorld facility in San Antonia, Texas. The calf was just three weeks old.

On May 24, 2015, a dolphin named Hana—one of only two dolphins the Vancouver Aquarium held in captivity—passed away shortly after undergoing bowel surgery at the facility in Stanley Park.

Before that, on February 19, 2015, a beluga whale named Nanuq died while on loan to a SeaWorld facility in Orlando, Florida.

Qila’s death this month leaves the Vancouver Aquarium with one beluga, named Aurora, still held in Stanley Park.

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According to a July 2014 park board report, the Vancouver Aquarium owns eight beluga whales (seven now that Qila has died). One is kept in Vancouver, four are housed at Sea World facilities in the United States, and two are on loan to the Georgia Aquarium in Atlanta. At least some of those animals housed in American aquariums are there on breeding loans. The terms of those arrangements can see the ownership of calves fathered by Vancouver Aquarium whales alternate between the Vancouver Aquarium and the American facility that housed the animal during the period of conception.