Orlando-based SeaWorld has faced sagging attendance along with criticism about its treatment of the captive marine mammals, and some activists had called for the end of public exhibition of killer whales, or orcas, altogether.

SeaWorld Entertainment Inc, which has parks in San Diego, Orlando and San Antonio, said in November it would replace its signature "Shamu" killer whale shows in San Diego with displays focused on conservation.

The company, whose shares rose as much as 6 percent in morning trading, also said it would scrap plans for a $100 million project called "Blue World" that would have enlarged its 7-million-gallon orca habitat at SeaWorld San Diego.

California regulators had approved the project, but only on the condition that the company cease captive breeding of orcas as well as the transfer of new killer whales to the park.

"These changes are something that advocates have been urging for years and I think SeaWorld will find that visitors will reward their actions with a renewed interest in the parks," California Congressman Adam Schiff, author of the ORCA Act, which seeks to phase out captivity of orcas, said in an email.

Some activists have called for SeaWorld to release its orcas into coastal sanctuaries. However, SeaWorld has said that whales raised or born in captivity would likely die in the wild.

SeaWorld also faced a backlash after the release of the 2013 documentary "Blackfish," which depicted the captivity and public exhibition of killer whales as inherently cruel.

Dr. Naomi Rose, a marine biologist with the Animal Welfare Institute who was an adviser to the film, said SeaWorld's move was a "monumental and important first step forward in achieving a more humane business model for the company."

Animal rights group People for Ethical Treatment of Animals (PETA) said SeaWorld had taken a step forward but renewed its call for the company to link its tanks to ocean sanctuaries.

SeaWorld, which has not collected orcas at sea for almost 40 years, has 29 killer whales under its care. The first killer whale in the company's care was born in a SeaWorld park in 1985. Since then, 30 have been born in the parks.

SeaWorld, which gets about 20 million visitors a year, said it would introduce natural orca shows in place of theatrical performances, focusing on exercise and the animals' health.

The changes will be implemented in San Diego next year and in its other parks by 2019.

SeaWorld also said it would 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.