Tuk was a sad old beast by time he died in 1997. 

Slowly roaming hang-jawed around his pen, the 37-year-old polar bear had been the only impediment to the official closure of the Vancouver Zoo in Stanley Park. 

The Vancouver Park Board had voted four years earlier to close the zoo; then, as now with the cetaceans at the Vancouver Aquarium, people hotly debated keeping mammals in captivity.

The bear had arrived at the relatively new zoo in the 1950s as a playful cub from the Northwest Territories, his mother shot by a Inuit hunter. 

Tuk joined the other animals at the zoo, most of them kept in small enclosures for display — as was the practice at the time. 

"That's the standards of keeping animals back then," said former zoo curator and researcher Vernon Kisling. 

"They didn't have the advanced knowledge we have today."

But as Tuk got older, the Vancouver zoo, like zoos around the world at the time, was looking to shift its focus from a menagerie of exotic animals to a wildlife conservation centre. For some, it was too late.

The zoo closed for good in 1997. Tuk, who was so old he couldn't be moved, died there.

This video, originally broadcast in 1993, captures the debate at the time:

From the archives: Vancouver zoo closes4:21

Kisling says zoos have constantly evolved over the hundreds of years they have been publicly available. 

"As professionals they want to make these improvements, but it's also because the public has constantly learned more about the environment over these many decades and they've learned more about these animals," he said.  

"And as they learn more, they expect more from the zoos and aquariums."

Leaders like the San Diego and Leipzig zoos have spent millions of dollars expanding and improving animal enclosures to make them seem more natural. 

But opponents maintain that no amount of change can justify keeping the animals in captivity in a zoo. 

If this all sounds familiar, it's because it is. 

Supporters and detractors of the Vancouver Aquarium have been having the same debate over its large mammals, the cetaceans, on display. Presumably people aren't as concerned about the fish tanks. 

Last week, the Park Board voted to ban the practice, much to the outrage of zoo officials and researchers who say it is an essential part of the organization's conservation efforts. 

Kisling is on their side. 

"I know there's a lot of people that would like to close zoos and aquariums, but the fact is that these facilities are really important to the education of the people and to wildlife conservation," he said. 

A Pacific white-sided dolphin, a harbour porpoise, and a false killer whale remain at the Vancouver Aquarium — all of them were rescues. 

According to a staff report, the aquarium has plans to spend $100 million on expansion, including its whale pools and a new Arctic exhibit with two beluga pools.

The report also says the aquarium planned to bring back two belugas, but it would phase-out beluga displays entirely by 2029.