Baltimore’s National Aquarium in Maryland, US, has announced it is considering retiring its eight bottlenose dolphins and moving them to a unique oceanside sanctuary.

The proposed move comes at a time when aquariums are under fire for holding large, intelligent animals in captivity, with the National Aquarium shifting its focus from being a mainly tourist attraction to becoming a nationally-recognised conservation organisation.

In a statement, aquarium director John Racanelli said: “We are studying and evaluating all possible options for providing them with the best possible living environment in the years ahead.”

Studio Gang Architects is currently looking into designs for a possible sanctuary and has discussed the plan with several dolphin and whale biologists.

Dolphins and other marine mammals kept in captivity suffer from chronic stress and behavioural abnormalities, such as odd repetitive movements, self-mutilation, and aggression, according to scientists.

SeaWorld has been under pressure from animal rights groups following the release of the documentary Blackfish, which recounts the 2010 death of trainer Dawn Brancheau

caused by a 12,000-pound (5.4-ton) bull in Orlando, Florida, with the documentary claiming that by being kept in captivity for entertainment, the whale was driven to madness.

Speaking to National Geographic Lori Marino, dolphin cognition expert at Emory University said that partly because of Blackfish, the public is less enthusiastic about seeing cetaceans in captivity.

"All it takes is for one of these institutions to be the leader, and others will follow," said Marino. "I have a feeling that this will start to roll."