A beluga whale and a bottlenose dolphin have died at Marineland in Niagara Falls, according to Ontario's Ministry of the Solicitor General.

Marineland hasn't responded to questions from CBC, but ministry spokesperson Brent Ross said in an email that Marineland advised Animal Welfare Services (AWS) that necropsies of both animals were conducted by professionals.

That marks three reported deaths of marine animals at the theme park in two months.

Kiska, the last captive killer whale in Canada, died in March.

The deaths have animal rights groups and activists concerned.

"This is something that needs immediate intervention," said Phil Demers, a former Marineland trainer-turned-whistleblower.

Michèle Hamers, World Animal Protection's wildlife campaign manager, said in an emailed statement there needs to be more transparency and accountability.

"It raises many questions around the state of care and reinforces ongoing concerns around the well-being of the rest of the animals at the facility," Hamers said.

Hamers said the province should launch an investigation into the animals' deaths and conditions at the facility.

"We are calling on Ontario's Solicitor General Michael Kernzer to urgently implement stronger regulations and enforcement to protect the health and welfare of the remaining animals at Marineland and in other under-regulated zoos and facilities across Ontario before more animals suffer and someone gets hurt."

Ross said AWS "continues to conduct compliance inspections" at the park to "determine if the standards of care are being met."

"AWS will not hesitate to issue orders if Marineland is not in compliance with all rules, regulations and standards of care regarding the welfare of animals," he said, pointing to when the ministry previously ordered Marineland to fix a broken water system that was leaving animals in distress.

Marineland appealed the order and it's unclear what has happened since.

"Due to the ongoing inspection by Animal Welfare Services, the ministry cannot provide further detail," Ross said.

Demers said he doesn't believe the park should be able to keep operating.

"I'm out of my mind. There's no accountability," he said, adding he and other activists will lead a demonstration outside Marineland on May 20.

Marineland has faced scrutiny in recent years for its alleged treatment of animals.

Animal Justice lodged a legal complaint in July 2021 against Marineland's treatment of Kiska, accusing it of breaking the law by not meeting her physical and mental needs.

The complaint followed videos posted by Demers that appeared to show Kiska floating listlessly and moving slowly.

Later that same year, Marineland was charged criminally after Animal Justice filed another complaint alleging dolphins were being forced to perform for entertainment despite a national ban.

The charges were stayed in December 2022.