Published: 2019-09-06 03:04:09 BdST
The results ruled out the presence of large animals such as dinosaurs, they said.
But there was a lot of eel DNA in the Loch, Professor Neil Gemmell, a geneticist from New Zealand's University of Otago, told reporters.
"Eels are very plentiful in the loch system - every single sampling site that we went to pretty much had eels and the sheer volume of it was a bit of a surprise," Gemmell said.
"We can't exclude the possibility that there's a giant eel in Loch Ness but we don't know whether these samples we've collected are from a giant beast or just an ordinary one - so there's still this element of 'we just don't know.'"
Gemmell noted however that despite the idea of a giant eel having been around for decades, nobody had ever caught a giant one in the Loch.
The international team of scientists took their samples of so-called environmental DNA (eDNA) in June last year.
The use of eDNA sampling is already well established as a tool for monitoring marine life like whales and sharks.
Whenever a creature moves through its environment, it leaves behind tiny fragments of DNA from skin, scales, feathers, fur, faeces and urine.
This DNA can be captured, sequenced and then used to identify that creature by comparing the sequence obtained to large databases of known genetic sequences from hundreds of thousands of different organisms.
The first written record of a monster relates to the Irish monk St Columba, who is said to have banished a “water beast” to the depths of the River Ness in the 6th century.
The most famous picture of Nessie, known as the “surgeon’s photo”, was taken in 1934 and showed a head on a long neck emerging from the water. It was revealed 60 years later to have been a hoax that used a sea monster model attached to a toy submarine.
Countless unsuccessful attempts to track down the monster have been made in the years since, notably in 2003 when the BBC funded an extensive scientific search that used 600 sonar beams and satellite tracking to sweep the full length of the loch.
The most recent attempt was three years ago when a high-tech marine drone found a monster - but not the one it was looking for. The discovery turned out to be replica used in the 1970 film “The Private Life of Sherlock Holmes”, which sank nearly 50 years ago.
Gemmell’s team included scientists from Britain, Denmark, the United States, Australia and France.