A petition to make it illegal for Californian marine parks or zoos to use orca whales for entertainment purposes has gathered 200,000 signatures.
The campaign, which focuses on US chain SeaWorld, reached the milestone on Sunday morning.
It follows proposals from California state legislator Richard Bloom, who introduced the Orca Welfare and Safety Act in Santa Monica on Friday.
“There is no justification for the continued captive display of orcas for entertainment purposes”, Bloom said in a statement.
“These beautiful creatures are much too large and far too intelligent to be confined in small, concrete pens for their entire lives. It is time to end the practice of keeping orcas captive for human amusement.”
The petition, on the campaign website SumOfUs.org, said the proposed legislation “could change everything”. But SeaWorld, which has three parks across the US including one in San Diego, criticised Bloom’s bill.
“The premise behind this proposed legislation is severely flawed on multiple levels, and its validity is highly questionable under the US and California constitutions”, its San Diego park told the LA Times.
Meanwhile, San Diego mayor Kevin Faulconer said there were “much more pressing issues” to address, adding that SeaWorld was a “critical part” of the city’s economy.
SeaWorld has emerged as the main focus of the SumOfUs petition – and by association the bill that was tabled on Friday – partly because of the 2013 documentary Blackfish. The damning film focuses on one of the orcas held by SeaWorld – Tilikum, which was involved in the deaths of three people – and the controversy over holding killer whales in captivity.
The petition argues that the “mental effects” of Tilikum being locked in a relatively small container were to blame for his role in the tragedies.
If passed, the Orca Welfare and Safety Act would make it illegal to capture orcas and hold them in captivity for public performances. Those found to be doing so could be fined up to $100,000 (£60,000) or face six months in a county jail.