The effects of the documentary Blackfish are plain to see for SeaWorld, as shares in the company have tumbled 33 per cent since the controversial film’s release.

SeaWorld has suffered severe backlash from the documentary film, which recounted the violent behaviour of an orca “driven to madness” in captivity, leading to the death of trainer Dawn Brancheau in 2010.

Shares fell 33 per cent after a 6-7 per cent decline in revenue for the company was forecast, with falling attendances and major sponsors and supporters distancing themselves from the company – driven in part by the negative press generated by the documentary – a major factor in the significant drop.

Blackfish looks at Tilikum, an orca kept in captivity who is responsible for the death of Brancheau in 2010 and two other people in the 1990s. The documentary suggests his violence was driven by the state of his captivity, while also suggesting captive lifestyles significantly shorten an orca’s lifespan.

Blackfish has become a cult hit, garnering 21 million viewers when it initially aired on CNN, with more and more watching on a daily basis. It prompted protests not only at SeaWorld, but at aquariums worldwide which are holding large sea mammals in captivity. Following the documentary’s release, various music artists who were set to play at SeaWorld cancelled performances, while big name supporters and sponsors publicly turned their back on the company in response.

SeaWorld and its Orca trainers have defended their methods, with Mark Simmons – a former trainer at the park – calling the documentary “a crusade against SeaWorld and zoological care in general, engineered by a perfect marriage between sensational animal rights organisations and disgruntled ex-SeaWorld employees.” The family of Dawn Brancheau have also slated Blackfish, stating: “Dawn would not have remained a trainer at SeaWorld for 15 years if she felt that the whales were not well cared for.”

In the wake of the controversial documentary, state legislation has been proposed for California, which would mean SeaWorld would no longer be able to have orca shows in that state, while a recent ruling in Vancouver means cetaceans can be kept but under strict breeding rules.