There’s a red herring mixed with the Oak Bluffs sharks, and it’s time for us to get on deck and do some sorting.

The Humane Society of the United States last month released a video shot by an undercover investigator at the most recent Oak Bluffs Monster Shark Tournament. The video, together with the accompanying letter, showed that the tournament is, in addition to being a cruel spectacle, quite probably a major illegal gambling operation. It is one more reason why the tournament should be shut down forever.

Some Oak Bluffs officials, along with tournament organizers, seem to be trying to use the video as evidence that The humane society is really targeting Oak Bluffs, rather than the inhumane tournament and its impact on shark species that are moving rapidly toward extinction. They’re allowing a tiny part of the video to be used as a red herring that distracts everyone from the video’s overwhelming evidence that the tournament is a gambling enterprise, an exercise in cruelty, and a poor excuse for a sport that wastes the lives of sharks and contributes to their decline.

The video does show an Oak Bluffs police officer at the scene as some bets are being placed, and notes that the tournament sponsors provide some proceeds to the local police and harbor patrol. But there was hardly any suggestion of complicity. I assume the police thought, or had been assured, that the event was not illegal gambling.

But that’s a determination to be made at a higher level, which is why we forwarded the evidence we gathered to Massachusetts Attorney General Martha Coakley.

There was no attack meant or implied against the Oak Bluffs police department. It’s simply not an issue for us.

What is an issue is that sharks are being killed for no good reason. As our video documented, one boat in the monster shark tournament brought in a blue shark, a near-threatened species in serious decline, and not even eligible as a tournament entry. Other boats released sharks after long battles, but often with the hooks still snagged in their mouths — fish that may not have survived the experience. And some killed sharks far too small to qualify as an entry.

It’s certainly also an issue that hundreds of thousands of dollars changed hands in the contest, which is, we believe, illegal under Massachusetts law in several ways — as a lottery, in betting pools and in raffles held by a for-profit entity, Sharks Unlimited. Our analysis indicates that these are potentially criminal violations of Massachusetts law and we have asked the attorney general to investigate and, as appropriate, prosecute.

The fact that the tournament appears to be a criminal enterprise is one more reason why it should leave Oak Bluffs forever. One more reason, too, why shark tournaments should be halted everywhere, since most of them follow the same pattern, with boat owners and crews placing large bets that they call Calcuttas.

And while the comparatively small number of sharks taken in these tournaments isn’t numerically the biggest factor in the decline of the shark populations, the contests are a high-profile activity, getting extensive coverage by many of the media, and thus implicitly encouraging more people to go out and kill sharks. By glamorizing the shark hunt, they encourage it and prey on our society’s fears of sharks and the perceived need to kill them. And the money from gambling on tournaments just fuels the whole sordid spectacle.

With most shark species in dire condition, we should be doing everything we can to keep these beautiful, and necessary, predators alive — and to protect them and allow their numbers to rebound. Shark tournaments encourage just the opposite. Our investigation provides even more reasons that shark tournaments should be halted, now.

John Grandy is senior vice president for wildlife protection at The Humane Society of the United States.