UPDATE: Cheap Trick and REO Speedwagon have canceled SeaWorld shows as well.

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In October, CNN aired a documentary called Blackfish that, in the wake of SeaWorld trainer Dawn Brancheau’s death by orca, raised questions about the humaneness of keeping “killer whales” in captivity. Now, a number of musicians who were scheduled to play SeaWorld have backed out, some of them citing concerns after seeing the film.

Heart’s official band account and Barenaked Ladies frontman Tyler Stewart both issued tweets expressing their misgivings:

Barenaked Ladies offered further explanation in a statement:

This is a complicated issue, and we don’t claim to understand all of it, but we don’t feel comfortable proceeding with the gig at this time. The Seaworld folks have been gracious, and extended us invitations to the park to learn more about what they do, and how they do it.

Willie Nelson has also canceled a SeaWorld performance. Nelson cited scheduling conflicts, but SeaWorld spokesman Nick Gollattscheck’s statement to CNN seems to assume Nelson’s real reason for backing out was Blackfish-related public pressure. Gollattscheck:

While we’re disappointed a small group of misinformed individuals was able to deny fans what would have been great concerts at SeaWorld by Heart, Barenaked Ladies, and Willie Nelson, we respect the bands’ decisions.

Meanwhile, the AP reports that Joan Jett has asked SeaWorld to cease using “I Love Rock ‘N’ Roll” as entrance music for the Shamu Rocks show. In a letter, Jett explained, “I’m among the millions who saw Blackfish and am sickened that my music was blasted without my permission at sound-sensitive marine mammals.” SeaWorld’s Gollattscheck responded that Jett’s music was fully licensed for use, but the Shamu Rocks show is being replaced by another production with different music.

Shamu remains unavailable for comment. Here’s the Blackfish trailer: