Fin

To Ancient Roman emperors and, later, the court of Versailles, larks' tongues were a delicacy - a real one, served with wine but without the rest of the bird. To dine like this sounds so extravagant and ridiculous now that no attempt to reinstate the dish has lasted long, and yet every year over 70 million sharks are slaughtered just so people can eat their fins in soup. With a rapidly dwindling shark population worldwide and ecosystems at risk of collapse without their top predators, this culinary fad has created a real crisis. If the situation cannot be turned around within the next few years, it will be too late.

For those of us who grew up when Jaws was the talk of the town, sharks will always be a source of fascination and terror. That's probably why Shark Week took off when it did, and it's certainly why Eli Roth was so thrilled when asked to become one of its hosts. The Cabin Fever director has a real soft spot for the cartilaginous critters and a degree of naivety, too, which makes him the perfect choice for this documentary. No amount of experience dealing in counterfeit gore can prepare somebody for the horrors of the real thing, yet Roth's background means that no-one is likely to mistake him for a sentimentalist. His reactions to what he sees in the course of this film feel wholly genuine, and are understandable.

Laws are now in place in most countries requiring that if a shark is caught for its fins, the whole body must be landed, yet there is still footage here of sharks on the boat of a deck having their fins sliced off whilst they're still alive and then being thrown back into the ocean. You don't need to be familiar with their physiology or to be told that they feel pain as we do to recognise their agony, and that's not the worst of what's on display in scenes which some of Roth's most hardcore fans will struggle to watch. The filmmaker himself is visibly upset and there are moments when you will wonder at his ability to keep on working. In one scene he desperately negotiates to try and buy a shark so it can be set free, but it's clear that the people he's with can't make sense of his words. This is far from traditional, neutral journalism, but it's effective, and it's also unnecessary to sustain the argument for change, as the facts and figures provided (all easily verifiable) do that by themselves.

There are occasional slips. "Sharks are different from fish," says one participant, which is a dubious claim to begin with but the more so when he tries to support it on the basis of their reproductive strategy - lots of fish species bear live young in relatively small numbers. The really important number to note here is the number of years it takes for most sharks to reach sexual maturity, because this is what makes it clear how difficult it is for them to recover at the population level - even from the damage that has already been done. Roth's tendency to take things at face value becomes an advantage, however, when he was other people to guide him, as it makes it easier to see how strategies aimed at maintaining public ignorance about the shark fishing industry work, and it also encourages others to open up more than they otherwise might.

As the film tracks the severed shark fins' destination, we get into the murky world of organised crime, barely regulated capitalism (not a wholly separate thing) and marketing hype which recalls that behind the tulip mania of the 1630s. Tulips at least look pretty. Does shark fin soup even have flavour? Not a very distinct one, concludes Roth, comparing it with an artificial substitute. Eating it with ham broth, having owned a pet pig, he is in his own personal Green Inferno, a scene made more compelling by his choice of a fellow horror director as his dinner companion. There's more to disgust him, though, as he reflects on the way he has seen the fins dried and stored, raising the question: might film and photography be used to disgust the people who currently pay high prices for this supposed delicacy?

A wide-ranging film which seems to keep evolving as it goes along, Fin is disturbing for a purpose, as it absolutely ought to be. There are also brief, magical scenes where Roth, underwater, cuddles and pets a wild shark as if it were a dog. Virtually everything told here is also shown, and here film serves another purpose: as a record of what may never be seen by human eyes again.