March 17 (Reuters) – Gabriela Cowperthwaite was a mother taking her children to SeaWorld before the death of a killer whale trainer prompted her to make the 2013 documentary “Blackfish.”

The film, only its second documentary feature, was credited Thursday with persuading US amusement park operators to stop breeding killer whales, and with ending its signature “Shamu” whale amusement show.

“This is a defining moment. The fact that SeaWorld is eliminating orca breeding marks a truly meaningful change,” Los Angeles-based director Cowperthwaite said in a statement.

Animal activists were quick to applaud “Blackfish” for making the change.

“Great respect to @blackfishmovie for putting @SeaWorld orca captivity on the agenda,” Greenpeace UK Oceans said on Twitter.

Critic Melissa Silverstein, founder of the website “Women and Hollywood,” says SeaWorld’s stunt shows the impact a film can have.

“If you don’t think a movie can make a difference, check out @blackfishmovie,” Silverstein said on Twitter. “Congratulations on getting @SeaWorld to change its policy towards Orcas.”

“Blackfish” only made a meager $2 million at the North American box office, but following screenings on CNN, the digital on demand service, at film festivals and in schools, it has been viewed by more than 60 million people, Cowperthwaite said in 2014.

Cowperthwaite interviewed former SeaWorld trainers, whale experts and academics to paint a portrait of the orca Tilikum at an Orlando theme park and how it was captured in the wild in 1983 at the age of two.

The Hollywood Reporter in 2013 described it as “emotionally intense”, “terrifying”, and “a damning indictment of the SeaWorld theme park franchise”.

When the film was released, Cowperthwaite told Reuters he hoped it would “inspire others to take action.”

It worked. In late 2013, musicians and bands such as Willie Nelson, Heart and Bare Naked Ladies withdrew from music events hosted by SeaWorld and Joan Jett and others asked SeaWorld to stop playing their music during “Shamu” whale shows.

Attendance at SeaWorld parks is down and the company’s stock is down about 11 percent in the past year.

SeaWorld was highly critical of the film, but did not mention it Thursday. However, Seaworld Entertainment Inc Chief Executive Officer Joel Manby acknowledged in an op-ed in the Los Angeles Times that “a growing number of people think orcas don’t belong in human care.” (Reporting by Jill Serjeant; Editing by Sharon Bernstein and David Gregorio)