After a multi-year legislative battle, a bill to outlaw keeping cetaceans like whales and dolphins in captivity has cleared the Senate — all but ensuring the end of a once-popular theme park attraction in Canada.

S-203 — first introduced by now-retired Liberal senator Wilfred Moore in December 2015, with the backing of Green Party Leader Elizabeth May — would ban keeping and breeding these marine mammals in captivity through amendments to the Criminal Code.

Fines of up to $200,000 could be imposed on parks flouting the law — a sum set deliberately high as a deterrent.

I have been there. I have been to the Vancouver Aquarium. I see the joy on these cetaceans faces' — on the belugas' faces — when they come out and get food. - Conservative Manitoba Sen. Don Plett

The bill finally cleared the Red Chamber Tuesday night after nearly three years of debate and study. It now will be shuttled through the House of Commons by May.

The bill has the support of MPs from across the political spectrum, including Liberal Nathaniel Erskine-Smith, Conservative Michelle Rempel and New Democrat Fin Donnelly.

Conservative MP Michelle Rempel supports Bill S-203, which would ban keeping or breeding cetaceans in captivity. (Sean Kilpatrick/Canadian Press)

The bill's passage in the upper house comes after years of advocacy work by animal welfare advocates, who have long argued that holding these highly intelligent creatures in concrete tanks is a cruel and perverse form of entertainment.

The fight for cetacean rights picked up considerable public support after the release of the 2013 documentary film Blackfish, which documented some of the perils involved in holding whales, dolphins and porpoises in parks like Sea World.

The Senate bill really has two targets in mind: the Vancouver Aquarium and Marineland in Niagara Falls, Ont.

The Vancouver Aquarium once defended holding these mammals in captivity on both scientific and educational grounds, but recently said it would no longer display whales or dolphins at its facility as protests over captivity have become a "distraction" for the business.

Marineland has been a vocal opponent of the Senate bill, saying it would devastate attendance — and threaten conservation efforts — at theme parks where these animals are on display. It has also said the bill threatens the seasonal employment of hundreds of local residents during the summer months.

Marineland's owner, John Holer, testified at a Senate committee before his death last summer, asking senators to halt the bill. Today, Marineland issued a statement calling S-203 anti-science.

"Bill S-203 was not supported by the relevant ministries or the credible scientific community," says the statement. "Sadly, it impairs legitimate scientific and research programs and is explicitly targeted to close Marineland.

"The bill and the debate around it (have) been highly emotional, lacking in fact-based or science-based analysis and mired in unnecessary conflict incited by radical animal rights groups from the United States."

The Senate bill would, through the breeding ban, phase out captivity over time. That means Marineland would still be able to keep its current stock of some 55 cetaceans even if the legislation is passed by the Commons.

The hope of many activists is that some or all of the marine mammals currently in captivity in Canada eventually would be moved to an open water seaside sanctuary in either B.C. or Nova Scotia.

The bill would also prohibit the importing of cetaceans, or their sperm, tissue cultures or embryos.

Holler had an ally in Conservative Manitoba Sen. Don Plett, who has steadfastly opposed the Senate bill. Plett continually sought to put off a vote through the creative use of some parliamentary procedure.

The Senate fisheries committee, of which Plett was a member, studied the bill for some eight months over 17 committee meetings with more than 30 witnesses — considerably more time than a Senate public bill typically spends under scrutiny at committee.

Conservative Manitoba Sen. Don Plett poses for a picture with John Holer, the owner of Niagara Falls' Marineland. (Twitter)

Plett relented Tuesday night — but not without defending the record of these facilities.

"I asked the sponsor of this bill, Sen. Moore, and other members of the fisheries committee whether any of them had ever made a trip to Marineland to inspect this 'horrendous' facility that everybody is talking about — to inspect this small little bathtub that these whales are swimming around in," he said.

"I have been there. I have been to the Vancouver Aquarium. I see the joy on these cetaceans faces' — on the belugas' faces — when they come out and get food."

Meanwhile, another Manitoba senator, Independent Sen. Mary Jane McCallum, painted a vivid picture of these parks as terrible places for marine mammals.

"An adult female beluga whale lying motionless below the body of her dead baby calf; an orca lying motionless on her side, floating towards the top of the tank, heavily sedated from an accidental overdose of Valium; a sharp, rust-coloured, steel-edged grate covered in blood, the result of carelessly transporting a beluga whale between tanks," she said.

"Finally, an indoor tank lacking both natural light and quality air ventilation, and now a sickly green colour caused by a breakdown in the disinfection unit ...

"These disturbing visuals I have painted for you are actual photographs submitted to the standing Senate committee on fisheries and oceans by a former marine mammal trainer."

Senate passes shark fin ban

The Senate passed another animal welfare bill Tuesday: S-238, which will ban the import and export of shark fin products.

Conservative Nova Scotia Sen. Michael MacDonald, who tabled the bill, has said the practice has done vast damage to the world's shark population — which has declined nearly 80 per cent over the last 50 years.

Canada is the world's third largest importer of shark fins, surpassed only by mainland China and Hong Kong, where shark fin soup is a popular delicacy among the wealthy. In 2015 alone, Canada imported over 144,000 kilograms of shark fins.

"Tens of millions of sharks are left to die every year for nothing but the prestige associated with a bowl of shark fin soup," MacDonald said.

That bill will now be sent to the Commons for further debate among MPs.