On a fall evening nearly eight years ago, the Vancouver Park Board convened a special meeting to discuss a controversial plan to expand the city's aquarium. The proposal, which involved a related bylaw on captive cetaceans, had been a hot issue for months: supporters and opponents alike signed petitions and wrote letters to the editor, the public demanded a referendum, and a survey showing overwhelming support for the expansion was blasted as misleading. The meeting was ripe for heated debate.

But in the end, 15 of 51 scheduled speakers failed to show, and 21 of those who did attend supported the expansion plan. All but one park board commissioner voted in favour of it; a commissioner who was also an aquarium staffer did not vote. The decision was made with relative ease, with a few notable caveats: that a by-law relating to captive cetaceans be removed from the aquarium's 20-year lease to allow the possibility of discontinuing the display of cetaceans at any time; and that the park board revisit the issue in 2015.

On Saturday, the park board will review the practice of keeping whales and dolphins at the Vancouver Aquarium, with city staff and aquarium representatives scheduled to make presentations. About 100 people have signed up to speak, which could draw the meeting out over a few days.

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"The aquarium has known since November of 2006 that there was a strong possibility that these bylaws would be reviewed," park board chair Aaron Jasper said.

The issue has popped up several times over the years, but it was brought into sharp focus in April when some park board commissioners, and later the mayor, voiced support for phasing out captive cetaceans.

Mr. Jasper noted that while it is not yet 2015, the park board has an "obligation to provide some certainty" to the aquarium before it proceeds with the next phase of its latest expansion. However, he conceded a new board could make the decision after November's civic election.

On Wednesday, the park board released a report it commissioned from Joseph Gaydos, chief scientist for the UC Davis Wildlife Health Centre's SeaDoc Society Program. It found that while Vancouver's aquarium either meets or exceeds North American industry standards, more research – including potentially a "large-scale scientific study on the welfare of captive housed cetaceans" – would be needed to evaluate the ethics of the practice. Dr. Gaydos will present his findings on Saturday.

Mr. Jasper, who said he wrestles with the ethics of keeping cetaceans in captivity, said he has no interest in making a rash decision.

"If, after we talk with the author of this report, after we talk with the aquarium, and we hear from the public, if we don't feel we have enough information, then I think we have to be cautious about taking any action," he said.

Commissioner Sarah Blyth, who opposes keeping cetaceans at the aquarium, said the park board has received about 20,000 e-mails on the matter in recent months and has a "binder filled with letters, hand-written from children in schools." Blackfish, a 2013 documentary about orcas at SeaWorld, heavily renewed public interest, Ms. Blyth said.

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Louie Psihoyos, director of the documentary The Cove, which explores dolphin hunting in Japan, and four former SeaWorld trainers featured in Blackfish have written to the park board urging it to phase out captive cetaceans.

The B.C. SPCA has proposed a "sunset bylaw" that would permit the aquarium to keep cetaceans it currently has, as well as rehabilitated ones deemed non-releasable, but prohibit breeding and breeding loans of cetaceans. Dr. Gaydos's report notes that while the Vancouver Aquarium has only two belugas on-site, it owns nine in all. Five are at SeaWorld and two at the Georgia Aquarium.

The Vancouver Aquarium unveiled phase one of a new, multi-phase expansion last month. It includes galleries, programs and a courtyard – although installation of new, larger beluga whale and dolphin tanks isn't scheduled to begin until late next year.