Another sad chapter in marine park history has come to a close. Tilikum, the world's largest captive marine mammal, passed away Jan. 6 at Sea World Orlando after a lengthy illness.

According to SeaWorld officials, the cause of the 36-year-old whale's death is yet unknown. The most likely culprit, they suspect, was an incurable lung infection first diagnosed last March.

"Tilikum had, and will continue to have, a special place in the hearts of the SeaWorld family, as well as the millions of people all over the world that he inspired," President & CEO of SeaWorld Joel Manby said in a statement. "My heart goes out to our team who cared for him like family."

Captured and separated from his family at the age of 2 off Iceland in 1983, Tilikum became a prominent star of orca shows at SeaWorld. He was also involved directly in the deaths of three people, with SeaWorld Orlando trainer Dawn Brancheau's drowning in 2010 the focal point of the documentary "Blackfish."

"He lives in tremendous pain. He has caused tremendous pain," movie director Gabriela Cowperthwaite said earlier last year. "And he has been kept in similar conditions despite all these tragic lessons because he was a top breeder and he splashed audiences really well. So this news is no sadder than the story of his life. And unless SeaWorld changes we’re left with no lesson. Just a really sad story."

Reaction to Tilikum's passing on social media ranged from sadness to anger, with animal rights advocates pointing to his three decades of captivity as yet another reminder of the cruelty of marine parks.

While SeaWorld remains adamantly against exploring the idea of releasing its remaining captive orcas into sea pens, the company is taking steps to phase out the giant mammals. Last March, officials announced plans to permanently end both its orca breeding program and killer whale shows. Because so many of its nearly two dozen captive killer whales are so young (including one newborn expected to arrive in the spring), SeaWorld's true grip on orcas won't end for several decades.

"Manby should continue to listen to the public, which is now asking for SeaWorld to close the chapter of captive orca history by retiring the remaining whales and, at a minimum, allowing them the opportunity to swim wild under close supervision of human care in ocean enclosures," Jean-Michel Cousteau, president of the Oceans Future Society, recently told the LA Times. "Let's retire these intelligent, social, complex animals to seaside sanctuaries."

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.