The Loch Ness monster could be a giant eel, according to a fishy new theory that will keep Highland tourists guessing.

In one of the biggest DNA studies of its kind, a team of scientists from New Zealand’s Otago University found the presence of about 3,000 species in the deep murky waters of the Scottish loch.

Most of the creatures were very small, and while they did detect DNA from pigs, deer, sticklebacks and humans, there were no monsters. But Prof Neil Gemmell, who led the study, said he couldn’t rule out a theory that eels in the loch have grown to an extreme size.

“It is possible there are very large eels,” Gemmell told a packed press conference at the Loch Ness Centre at Drumnadrochit, “but it depends how big you think ‘large’ is.”

The eel theory resurrects a possible explanation for “sightings” of the monster that date back to 1933, when the Inverness Courier first reported a “strange spectacle on Loch Ness”.

In the decades since, there have been dozens of high-profile attempts to prove the existence of the monster. In 2003, the BBC funded an extensive search using 600 sonar beams, which turned up nothing.

Gemmell said the sheer volume of eel DNA surprised him and his team. And, maintaining a straight face, he added: “We don’t know if the eel DNA we are detecting is from a gigantic eel or just many small eels.”

Looking more sceptical, he outlined the theory: “The notion is that these eels would normally migrate to reproduce, but they, for whatever reason, don’t. And they continue to grow to a very large size, forgoing reproduction for growth.”

He said, however, that no giant eels have ever been caught. And when it was pointed out that the record catch for a European eel is 5.38kg, Gemmell said: “It doesn’t sound like a monster, does it? But based on the evidence we’ve accumulated, we can’t exclude it as a possibility.”

One of the favourite Loch Ness monster theories is that it is an elasmosaurus or plesiosaur that somehow survived the extinction of the dinosaurs.

Gemmell was more certain about ruling this out. “Is there a plesiosaur in Loch Ness? No. There is absolutely no evidence of any reptilian sequences. So I think we can be fairly sure that there is probably not a giant scaly reptile swimming around in Loch Ness.”

His study sequenced DNA from 250 samples of Loch Ness water at a range of sites and depths. Reptilian DNA, he explained “should sit somewhere between crocodilians and birds. And there’s nothing remotely like that in our sequences. We found tonnes of birds. So yes, there are birds, we didn’t find crocodiles. We didn’t find lizards. We didn’t find adders. We didn’t find another relative, we did find toads, frogs and amphibians and they are obviously distantly related.”

The press conference had been called under slightly false pretences, Gemmell admitted. He said: “If you like, this has been a great big science con. We’ve been talking about science the entire time and we’re using the monsters as bait.” He said he hoped interest in the Loch Ness legend would raise the profile of environmental DNA research.

“I came into this with a view that there probably wasn’t a monster,” he said. “I wanted to understand the biodiversity of Loch Ness and we’ve done that very well.”

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Gemmell said the study would eventually provide a publicly available database of all the species in the loch, which could help gauge changes in biodiversity and the impact of invasive species such as pink salmon.

“We’ve communicated science in a way which has been more compelling than perhaps most of the science I’ve been involved in in my prior career,” Gemmell said. “More people now know about environmental DNA than ever before, I would imagine, and I think that’s a good thing. Because we need these tools to be able to document what is living in places as, slowly but surely, our world becomes less special.”

Gemmell was challenged about why the study had failed to detect the presence of otters or seals in Loch Ness. He said: “We may have missed things. But we found all the species we know are residents in Loch Ness in respect to fish.”

He added: “Like every other monster hunt there has been here at Loch Ness, we have found no definitive evidence of a monster. More and more studies providing more and more negative evidence cast more and more doubt on the possibility, but we can’t prove a negative.”

However, he denied that he had totally killed off the legend of the Loch Ness monster. “There’s still some level of uncertainty there, so there is still the opportunity for people to believe in monsters. Is it front page news? I don’t know. But we’ve captured some imaginations.”

That will come as a relief to the tourist industry that has thrived on the banks of the loch ever since the earliest sightings, to the extent that nearby Drumnadrochit can support two competing Loch Ness attractions, Nessieland and the Loch Ness Centre and Exhibition.

• This article was amended on 9 September 2019 to more fully quote Gemmell on the study’s findings about DNA sequences.



