One of five beluga whales brought to Mystic Aquarium from Canada in May has died.
The male beluga had a preexisting medical issue, according to Mystic Aquarium.
"Veterinarians and animal care experts devoted the full capacity of their expertise to him, providing round-the-clock medical treatment, testing, and 24-hour monitoring. While he had shown signs of improvement from a gastrointestinal condition, we are deeply saddened to share that he passed away this morning," the aquarium posted on its Facebook page.
Get Connecticut local news, weather forecasts and entertainment stories to your inbox. Sign up for NBC Connecticut newsletters.
The whales arrived from Ontario in May after government officials from Fisheries and Oceans Canada approved the export of the animals. They range in age from 7 to 12 and were born in captivity and officials said they cannot safely be released into the ocean.
Connecticut-based Friends of Animals and other activists sought to block the transport in a lawsuit last fall against the U.S. Commerce secretary and National Marine Fisheries Service, which had approved the research permit. A federal judge in March declined to issue an injunction.
"This is a devastating loss for our staff and for the community, especially the animal care team who works closely with the belugas," Mystic Aquarium's post said.
