Tilikum in a scene from BLACKFISH (Gabriela Cowperthwaite)

Blackfish is most engrossing when it offers an alarming CSI-type forensic analysis into the 2010 death of whale trainer Dawn Brancheau at SeaWorld Orlando, by tracing the background of the cause: a killer whale named Tilikum.

First, the nomenclature for such large oceanic mammals can get confusing. The documentary’s title comes from what the Native American tribes of the Pacific Northwest traditionally call killer whales (and celebrate in legends). The largest member of the dolphin family, orca is the Latin genus specification, and has generally become a synonym for killer whale. In their natural habitat, these predators go after fish and smaller mammals, as seen here in some pretty dramatic wildlife footage, but not after humans (like in the 1977 thriller Orca). SeaWorld pretty much markets all the black-and-white patterned cetaceans as “Shamu.”

Director Gabriela Cowperthwaite continually returns to Brancheau’s enthusiasm and training experience through interviews with friends and co-workers, and witnesses vividly remember her shocking death (even for Florida, SeaWorld shows must be among the most photographed and filmed places by tourists). The resulting investigation by the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) placed limits on trainers’ interactions with the animals in the water—SeaWorld is appealing.

While SeaWorld claims to no longer obtain orcas caught in the wild for its U.S. parks anymore (among their eight-point, legalistic objections to the film that they’ve released publicly after not participating with interviews), others do, and such round-ups, like the one that caught Tilikum in 1983, are described by an old salt participant, who is still haunted by the sounds of the distraught animals. The film also tracks how SeaWorld sent off orcas that they’ve had problems with to less supervised facilities in other countries, without providing thorough warning on possible behavior issues.

Tilikum’s life is portrayed, year by year, in tearfully Dickensian terms, from an orphan living in captivity to isolation and abuse in a small British Columbian showcase, Sealand of the Pacific, where he was implicated in the death of a trainer there. Pointing fingers at a cover-up somewhere along the line, the documentary investigates what occurred. There are claims, and counterclaims from SeaWorld, at the OSHA hearing that the training staff in Orlando was not informed about Tilikum’s violent history so that he ended up not being carefully managed.

The most passionate interviews are with former SeaWorld trainers, though no indication is provided if they are disgruntled employees or converted activists against captivity in any facility, whether commercial or in a zoological aquarium. Speaking of the relationships they developed with individual killer whales through the performances (i.e., behaviors reinforced through feedings), ex-trainers tend to talk in the annoying anthropomorphisms they were instructed to use at SeaWorld, undercutting the credibility of the scientific explanations of the whales’ behavior in the wild and in captivity.

Throughout, the narrow focus on SeaWorld raises more questions that aren’t really considered. There’s no discussion of the U.S. or international legal framework beyond the possible OSHA violations that focus on working conditions for humans. Or, what changes are needed in the Marine Mammal Protection Act or in the regulation by the National Marine Fisheries Service? Activists say that almost half of the 45 killer whales now in captivity around the world, from Argentina to Japan, are in SeaWorld parks, but are orcas treated differently at other places, particularly at non-profit zoological parks?

Recently released as virtually a companion volume to the film, journalist David Kirby’s book Death at SeaWorld: Shamu and the Dark Side of Killer Whales in Captivity includes more background and details on the same trainers and witnesses, with additional clarifying facts and much more useful biological background on orca behavior. It supplements the experts sporadically interviewed. This film is not in the same investigatory league as Louie Psihoyos’s The Cove (2009), but if you didn’t feel guilty enough after seeing that award-winning documentary to stop taking your kids to marine park shows for the captive dolphins, this one will certainly shame you to resist the killer whale shows.

CNN has picked up the documentary for future broadcast.