Here we go again. Another shadowy image of something big swimming off the coast of the UK, another round of misguided man-eating shark speculation. When it comes to sharks, everyone thinks they are an expert. Unfortunately, although not unexpectedly, this results in a great deal of misinformation.

Over and over again, blurry photos are published along with fearmongering claims about what the images show. Those really in the know aren’t often consulted. Last year, for example, a photo of a shape in the waves behind children playing on a beach in California was covered globally as a near shark attack. But a simple analysis of the creature’s outline made it clear that .

And now comes the story of a video captured by a fisherman off the UK coast, a still of which is shown above, widely covered by news media. The Daily Mail newspaper ran it under the headline ““. It isn’t, but you wouldn’t necessarily have guessed that from the coverage. The shape of the fins suggests it is a basking shark, and an expert would have known that. But the Daily Mail drew on various sources claiming that it was a great white.

These included anonymous comments left on the fisherman’s Facebook page. The newspaper writes: “Common consensus on his Cornish Fishing Facebook page, where he posted the footage, was that it was either a great white or an oceanic great.” (An oceanic great doesn’t exist, by the way.)

Nonsense claims

A British shark angler is also quoted: “If the fish was 14ft long, it probably was a great white.” But other large species, such as basking sharks, are much, much, much more common in UK waters, so claiming that a big fish must be a great white is nonsense – if you hear hoof beats on Cornwall’s Bodmin moor, think horses, not zebras.

Finally there is a self-described “shark aficionado”, who said: “The more I look at it, the more it looks like a great white.”

Why quote a shark aficionado, a non-expert who thinks sharks are cool, for a story like this? Can you imagine if journalists did this for other types of story? The White House announced intentions to bomb Islamic State targets in Syria, but counter-terrorism aficionado Steve said that he’s pretty sure the organisation is actually hiding in Peru. Markets cheered the move to reduce interest rates, but finance aficionado John said that everyone should just buy gold and bury it in their backyards. It would never happen, because it’s ridiculous.

Stories about sharks touch on important issues such as human safety, coastal economies, global food security and the conservation of threatened species. It isn’t that hard to find qualified experts to comment, and these stories are certainly important enough to warrant making the effort. They certainly shouldn’t be open season for ill-informed speculation.

As a marine biologist, I may be a little biased when I tell you that sharks and their relatives are some of the most fascinating animals on the planet. There are more than 500 species of sharks, ranging in size from just a few inches to the size of a school bus. They come in an enormous variety of colours, including vibrant spots or stripes, and even bubble-gum pink. They’re found in a huge variety of habitats, from coral reefs to the Arctic, from right off our beaches to the deep sea. Sharks have big brains for their body size and many complex behaviours, including intricate social hierarchies.

With such a vast quantity of amazing real-life source material to draw from, you’d think that Shark Week, the Discovery Channel’s annual week of shark documentaries, which kicked off on Sunday, would never run out of stories that are both educational and entertaining. However, producers seem to prefer fearmongering and pseudoscience.

From watching Shark Week specials like this year’s I Escaped Jaws 2, you’d think that going into the ocean puts you at serious risk of being bitten by a shark. In reality, more people are killed by cows and toasters each year, and more people are bitten by other people in New York City than by sharks worldwide. Shark bites are so rare that multiple Shark Week specials have covered the same attack on several occasions.

Fooling viewers

This kind of fearmongering is not harmless. As many as 25 per cent of sharks and their relatives are considered threatened with extinction by the , and media coverage has been the public’s perception of sharks and willingness to conserve them. For years, a group of shark conservationists has Shark Week to focus on science and conservation instead of promoting fear, but pleas have been ignored.

As if this wasn’t bad enough, last year Shark Week decided to fool viewers and claim that the prehistoric is not actually extinct. I’ve spoken to more than 500 high school and middle school students about sharks in the past year, and I have yet to meet a school group that doesn’t ask me if the amazing news they saw on Shark Week about megalodon is true. A second programme, entitled Megalodon: The New Evidence, will air this year.

Hitler returns

Discovery’s executive vice-president for public relations Laurie Goldberg tweeted at me that of this year’s Shark Week specials, . Most. Things are so bad that when I jokingly suggested that the next logical step is for there to be a Shark Week special called Hitler Shark, I was told that this year’s Monster Hammerhead programme was for a while going to be called Hitler Shark.

Shark Week at its best can educate, entertain and inspire. Early instalments – it began in 1988 – are a big part of the reason why I became a marine biologist even though I grew up hundreds of miles from the ocean. Specials like the Alien Sharks series (the second one is airing this year,) which focus on the amazing biodiversity of deep sea sharks, represent everything Shark Week could and should be.

The phenomenal success of shows like Planet Earth demonstrate that fact-based programming can earn viewers, and the high ratings from last year’s Shark Week show that people will literally watch anything that has “shark” in the title. So how about focusing on the true, amazing and important things about sharks instead of pseudoscience and fearmongering?