Chants of "Empty the tanks! Empty the tanks!" could be heard as dozens of protesters gathered to protest the continued captivity of cetaceans at the Vancouver Aquarium.

"Your ticket supports dolphin cruelty, please think twice before you buy your ticket," protesters yelled at would-be aquarium visitors.

The Vancouver rally was one of 50 around the world calling for aquariums to “empty the tanks” and release whales, dolphins and other marine mammals. Rather than capturing marine mammals, for almost two decades the aquarium has relied on rescues or adopted animals that would have otherwise died.

Still, protestors like Janos Mate said the captivity is unwarranted.

"The educational value of watching whales and dolphins in a concrete tank is about the same as watching human beings in solitary confinement," Mate said.

Vancouver Mayor Gregor Robertson has expressed his opinion in the past, saying whales and other animals should not be held at the aquarium.

"My personal view is that the Vancouver Aquarium should begin to phase out the holding of whales and dolphins in captivity, " Robertson said in a statement in April.

Protestors welcome a review that is supported by both the park board and Mayor Robertson.

"We've been calling for a referendum for 20 years now,” Mate said. “We've given the Park Board over 20 to 30,000 signatures in various petitions in that regard."

Dr. John Nightingale is the Vancouver Aquarium director and said the thousands of signatures is a fraction of the one million visitors who come to appreciate the wildlife and conservation efforts. Nightingale said the goal for the aquarium is to spark conversation and encourage people to get involved in

"Our whole focus is on what I call 'growing the choir',” he said. “Getting people interested. Curious. Lighting that little spark that starts people up that ladder that eventually leads to some changes, like joining one of the on-shore clean-ups or choosing to buy sustainable seafood."

Larger tanks for whales and dolphins are part of the current $100-million expansion project at the aquarium.

With a report from CTV Vancouver’s Peter Grainger