Vancouver Aquarium has come under fire from animal welfare groups following the second death of a beluga whale at its facility in just less than a fortnight.

The 30-year-old beluga, named Aurora, died on 25 November, just nine days after her 21-year-old calf Qila – the first whale ever to be born in captivity in Canada. Both whales suffered from symptoms of abdominal cramping, loss of appetite and lethargy before their deaths.

A ruling by the Vancouver Park Board banning the breeding of captive cetaceans collapsed in November 2014, when it tried to push the ruling through at the last minute.

Following the deaths, Park Board chair Sarah Kirby-Yung – former vice-president of communications for the aquarium – said that the events justify a vote by city residents on continued whale captivity in the region, adding that she would be making a proposal to the board for this vote as part of the upcoming 2018 municipal election.

Speaking at a Marine Mammal Symposium in Vancouver, Lance Barrett-Lennard, head of the Cetacean Research Programme at Vancouver Aquarium, said that a cause of death had not yet been determined and that possibilities could include pathogens or toxins. He added that staff at the aquarium are “pulling out the stops” to discover the cause of death for both whales.

The aquarium now owns six belugas, four of which reside at SeaWorld in Orlando, with the remaining two calling Georgia Aquarium home. Including the recent deaths, the aquarium has lost three belugas since 2015, with a beluga – loaned to Orlando SeaWorld from Vancouver Aquarium – dying after an encounter with other animals in the tank in February last year.