Heart stars Ann and Nancy Wilson have opened up about their decision to scrap an upcoming SeaWorld concert in the wake of the controversial Blackfish documentary. The rockers joined the likes of Willie Nelson, Cheap Trick, REO Speedwagon and Martina McBride by pulling the plug on a scheduled gig at the Orlando, Florida themepark after watching the CNN movie, which exposed the bleak conditions for the captured killer whales housed at SeaWorld. Ann Wilson admits she and her sister were horrified by what they saw in the documentary, telling RollingStone.com, "It (Blackfish) really broke my heart and I just couldn't see signing my name to that... Before seeing the movie, I always imagined the orcas got to live in a big extended oceanic area when they weren't performing, but they live in a steel swimming pool and it basically drives them insane. "As the documentary pointed out, orcas' brains have a whole emotional section that ours don't even have. It's a whole social/emotional section and it tends to give them a real unified feeling among themselves. When mothers are separated from their young, they go insane. The genders stay apart in the wild and they have a matriarchal society, but SeaWorld just throws the two genders together. "Nancy and I didn't even originally realise the concert was at SeaWorld. We thought it was just somewhere in Orlando. I'm not making an excuse, but we just weren't paying attention to details. I've never been to SeaWorld. I've seen the photos of people getting splashed and it looks fun, but when you look underneath you see the dark side. What they do is slavery, plain and simple. It's like people saying, 'OK, let's go to Africa and bring a bunch of people back here'. There's never any way to make that OK." And she feels that those still performing shows at SeaWorld are acting like the stars who appeared in South Africa during apartheid when the world's top musicians had agreed to boycott the country. She explains, "We'd get these incredible, stupid money offers to come to South Africa and play Sun City. The people that did that - like Rod Stewart - slid in there, kept their eyes shut, played their songs and took the money. Our decision here was a little easier since all the facts were in the open." Sister Nancy adds, "I watched the documentary and could barely get through it. It was so upsetting and heartbreaking. I was also freaked out because I had made music for a nature documentary about orcas in the Northwest, called Baby Wild. It was railing against whales in captivity in general. "When this first came up, I thought, 'Should I feel guilty about making things hard for SeaWorld?' I've decided I don't have to feel guilty about this. We do hate to rain on anybody's parade, especially if it's someone's livelihood, but if it's at the expense of these animals that deserve so much better... then it it's worth a little scuffle."