Swimmers, beware! The numbers of the so-called bloodsucking "vampire fish" are on the rise in Britain's rivers. And if that doesn't scare you, did we mention that these creatures are also 1-meter long each?

The blood-hungry sea lamprey is a terrifying water creature. When hungry, they are also known to pounce on unassuming humans.

The lamprey also attacks and kills other water inhabitants by latching their razor-like teeth onto them and sucking the blood out, thus, the moniker "vampire fish."

There have been reports on record-breaking abundance in the following rivers and several websites have published recent sightings and have warned swimmers to be careful of these bloodsuckers.

The lamprey population in the United Kingdom has increased in recent years. This followed years of declining numbers because man-made barriers affected the water flow and prevented the ugly creatures to swim upstream to their breeding grounds.

"Now that water quality has improved and some of these barriers have been removed we are seeing lampreys return to the upper reaches of rivers such as the Ouse, Trent and Derwent, where they were absent as recently as 30 years ago," said fisheries expert Simon Toms of the Environment Agency.

Toms added that in the past 200 years, the rivers in the UK weren't able to support the lamprey's growth. Apart from the barriers, the poor habitat and water quality also played roles in decreasing their numbers.

Despite their looks, lampreys have a long history of being a favored delicacy in the Medieval Ages. And we're not just talking about that scene in the Game of Thrones where Tyrion Lannister ate a lamprey pie.

England's King Henry I was known to be a fan of the ugly fish. He died in 1135 after consuming "a surfeit of lampreys" in Normandy. It is believed that he suffered from food poisoning. However, that didn't stop the Royals from consuming lamprey dishes. This included King John, Henry's grandson.

There is a long-standing tradition wherein the city of Gloucester sends a lamprey pie to the English and British monarchs during Christmas. This tradition survived all the way to 1836, after which, the city only sends the holiday pie during jubilees and coronations.

In 2012, a traditional lamprey pie was sent to the Queen in honor of her Diamond Jubilee. Due to the low lamprey numbers in the UK that time, the fish used was imported from North America.

Photo: USFWS Midwest | Flickr

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