A false killer whale has died at the Vancouver Aquarium, becoming the fourth cetacean to die at the facility in the past year.
The aquarium said in a statement that Chester's behaviour changed Wednesday and despite intensive veterinary care, he died on Friday morning.
Chester was estimated to be just weeks old when he was found stranded on a beach near Tofino, B.C., in July 2014. He was in poor condition and had several wounds and lacerations on his body.
Dr. Martin Haulena, the aquarium's head veterinarian, said that stranded animals can have renal problems later in life, but he's waiting for the results of a post-mortem to determine Chester's cause of death.
The animal was given just a 10 per cent chance of survival when rescuers brought him to the aquarium's rescue centre.
False killer whales are members of the dolphin family and the aquarium said little is known about the species.
They get their name because they resemble killer whales. False killer whales are found in the waters around North American and Australia.
Fisheries and Oceans Canada determined in May 2015 that Chester could not be released back into the wild and the aquarium was asked to continue caring for him.
The aquarium now has just one cetacean, a Pacific white-side dolphin named Helen. After the Fisheries Department made its determination on Chester, the aquarium said he would be staying in the same tank as Helen.
Chester, who was named after Chesterman Beach where he was found, became a beloved member of the facility's family, but remained a "health challenged animal" throughout his life, the aquarium said in the statement.
"Chester connected with more than four million people during his time with us, sharing his joy and curiosity with every person he encountered. We've been incredibly lucky to love him and to learn from him," said Brian Sheehan, the aquarium's curator of marine mammals.
Last November, two beluga whales – 21-year-old Qila and her mother, 30-year-old Aurora – died nine days apart from what officials said was a mysterious illness.
In June, a nine-year-old rescued harbour porpoise named Daisy died. The aquarium said at the time that preliminary necropsy results showed the animal had pulmonary disease.
A bylaw passed by the Vancouver Park Board in May bans the aquarium from bringing any new whales, dolphins or porpoises to its facility in Stanley Park.