Animal activist Phil Demers, 44, claims the orca called Kiska has been there for the last 12 years.
He said she was captured in the North Atlantic Ocean in 1979 when she was three-years-old.
She was first taken to an aquarium in Iceland where she lived with four other young orcas, Mr Demers said.
These included Keiko, the star of the 1993 Hollywood classic Free Willy, he added.
Shortly afterwards, Kiska was sold, along with Keiko, to MarineLand, Mr Demers explained.
Kiska gave birth to five calves at the park, but all of them died at a young age, he claimed.
After spending over a decade completely alone at MarineLand, a video of Kiska banging her head against her tank went viral in 2021.
Mr Demers, the co-founder of the NGO ‘UrgentSeas’, posted another video of Kiska on UrgentSeas’ TikTok page that has also gone viral with 6.7 million views.
He claimed: “Kiska has been completely alone since 2011, which is tantamount to torture for social beings such as orcas.”
The former park trainer said: “The video was taken on 19 February this year. The footage was taken from a drone above the park.”
“This video demonstrates her loneliness and suffering,” he claimed.
Phil told Jam Press: “As someone who has worked with Kiska, watching her environment and health deteriorate as it has over the past decade has been heartbreaking and gut wrenching.
“During my time at MarineLand between March 2000 and May 2012, I worked with an array of marine mammals, including seals, sea lions, walruses, dolphins, and beluga and orca whales.”
Phil ran into trouble with the park when he launched his ‘Save Smooshi’ campaign to re-home a beloved walrus he worked with.
MarineLand filed a $1.5-million lawsuit against Phil for trespassing and planning to kidnap the 800lb walrus in 2012.
Phil filed a counterclaim for defamation and abuse of process.
Following lengthy negotiations, both parties agreed to drop the legal action and re-house Smooshi and her calf Koyuk to a new location.
He said: “MarineLand sued me for millions back in 2012 for my animal abuse allegations, but I successfully defended their decade of legal assaults to manage to negotiate the release of my walruses.”
Phil added: “My hope with our advocacy campaign is to highlight the plight of individual whales with the aspiration of retiring dolphins and whales back to the ocean and ending their senseless captivity.
“I believe with enough attention, this can and should be made possible for all captives.”
Phil told Jam Press: “We shouldn’t accept animal suffering nor should we remain quiet about it.”
TikTok users had a lot to say about Kiska’s plight following the release of the viral clip.
Serena commented: “It hurts so much, I’m crying this orca don’t deserve this. He/she should be at his/her family in the ocean, where they should be.”
Shailyn Fletcher said: “People say don’t let her go because she’s been captive but her soul would be more free dying in the ocean [than] that tank…”
Mike Playter wrote: “They’re working on a sale of MarineLand and hopefully a move for Kiska to the sanctuary in Nova Scotia.”
Someone else remarked: “It would be less cruel to let her go wild and see what happens rather than watch her die alone in this bathtub.”
Free Willy star Keiko died of pneumonia in 2003 in a bay in Norway, aged 27.
A MarineLand spokesperson told Jam Press: “Animal rights groups in Ontario sponsored a bill in 2013 that was passed into law that has made it illegal under Ontario law to bring another Orca into Ontario, even temporarily under strict conditions as a companion for Kiska, and Kiska is too old to be safely moved.”