SAN DIEGO (REUTERS) - SeaWorld said on Thursday (March 17) that it will stop breeding killer whales in captivity, bowing to years of pressure from animal rights activists, but the orcas already at its three parks will continue to live out their remaining years.

John Reilly, SeaWorld San Diego Park President spoke during a news conference on Thursday (March 17) and said, "We also reconfirmed our commitment to end theatrical orca shows and we will replace them with inspiring natural orca encounters."

SeaWorld, which operates marine parks in San Diego, Orlando and San Antonio, has a total of 29 killers whales, including six on loan to a park in Spain. Five of them were captured in the wild, but it has not caught orcas at sea for almost 40 years.

The parks have been criticized for their treatment of the captive marine mammals, with some activists seeking an end to public exhibition of killer whales altogether.

The criticism intensified after three orcas died at SeaWorld San Antonio within a six-month span in 2015.

"We love our whales," said Reilly. "And so do many of our visitors at SeaWorld. But we also know that whales have become a growing concern for many people."

SeaWorld, whose shares rose 8.2 per cent on Thursday (March 17), also said it will scrap plans for a US$100 million (S$135.6 million) project called Blue World to enlarge its 26.5-million-litre orca habitat at SeaWorld San Diego.

Some activists have called for SeaWorld to release its orcas into coastal sanctuaries, but the company says whales born or raised in captivity would likely die in the wild.

SeaWorld also said it will partner with the Humane Society of the United States and had set aside $50 million to push for an end to commercial whaling and seal hunting as well as the killing of sharks for their fins over the next five years.