No new whales or dolphins will be brought to tanks at the Vancouver Aquarium, ending a years-long fight by animal welfare activists who believe the highly social marine mammals are better off in the ocean.

On Monday night, the Vancouver Park Board voted 6-1 to ban whales, dolphins and porpoises in captivity on the property. The bylaw amendment, which came into effect immediately, also barred performances involving cetaceans.

The aquarium has said it plans to fight the decision and has not ruled out a legal challenge.

The last whales to live at the aquarium were two belugas, a mother and daughter named Aurora and Qila. They died last November after exposure to an unknown toxin.

Three cetaceans still live at the aquarium: one dolphin, one porpoise and a false killer whale, which is technically a dolphin. Under the new rules, the three marine mammals are allowed to stay at the aquarium, but aren’t permitted to perform in shows.

The decision leaves uncertain futures for five beluga whales currently on loan by the Vancouver Aquarium to U.S. facilities. The aquarium had been planning a $20-million beluga habitat – previously approved by the park board – expected to open in 2019. The Canada Arctic exhibit was part of a $100-million upgrade at the aquarium.

Before the vote, concern mounted that the decision could throw a wrench into the aquarium’s rescue program. According to the aquarium, it rescues more than 100 animals each year through its Marine Mammal Rescue Program.

Aquarium supporters rallied outside the meeting Monday. According to CEO John Nightingale, more than 12,000 people sent letters to the park board and Vancouver City Council speaking out against the change.

“Why would you rescue an animal and get it well, and then have to euthanize it because there’s no home? We’re the only home in Canada,” Nightingale said.

However, the decision does not affect the aquarium’s rescue centre, which is not on park land and therefore does not fall within the park board’s jurisdiction. The decision only affects the Vancouver Aquarium, which is nestled in Stanley Park on a 60-year lease from the city.

The board said the majority of the rescued marine mammals are eventually released, and those kept in captivity are mostly harbour seals, which were not included in the bylaw amendment.

“We’ve had backlash for the last few weeks, but the main goal is I think that we’re hoping that when this settles down that the decision made by the Park Board was seen as the right decision,” said Michael Wiebe, chair of the Vancouver Park Board.

Two decades ago, a similar vote banned polar bears at the aquarium.

In Ontario, the province passed a bill in 2015 prohibiting the breeding and acquisition of orca whales. It also introduced new rules requiring animal welfare committees at any facility that housed marine mammals, such as Marineland in Niagara Falls, Ont.

Nightingale insists that Vancouver Aquarium serves an important purpose in Vancouver, and that there are no plans to shut it down in response to the decision.

“The aquarium is not going to go away. It’s 60 years old, it’s got huge support in the community,” he said.

The amendment changed an earlier rule that prevented any cetaceans taken from the wild from being kept in captivity unless they were captured before September 1996, were part of an endangered species, or were injured or in distress.

On Saturday, protesters rallied outside the Vancouver Aquarium to call for a full cetacean ban. It was the fifth year in a row the “Empty the Tanks” rally was held.

Before the vote, the aquarium had said it planned to phase out its cetacean program by 2029, the same year its lease in Stanley Park ended.

With files from CTV Vancouver and The Canadian Press