The monster, which is from south-east Asia, can also "crawl" on land and survive out of water for up to four days.It already has a fearsome predatory reputation in other parts of the world.In the U.S., the fish has been described as a "FrankenFish" and "like something out of a horror film".
Andy Alder, from Lincoln, caught a 2ft snakehead while using a sprat as bait for pike on the River Witham near North Hykeham.He said: "It had a gob full of razor-sharp teeth. To be honest it looked terrifying."Anglers and conservationists are panic-stricken after its discovery in Britain.
An Environment Agency source said: “The reaction was, 'Oh s***'. This is the ultimate invasive species — if it starts breeding here it's a disaster."Ben Weir, of the fishing magazine Angler's Mail, said: "In all my time of working within fishing I have never heard so many concerned voices.
"These guys are the real deal and have attacked humans whilst protecting their young.
"Everyone within the angling and fishery world have been left gobsmacked by its capture."
Experts have examined pictures of the fish and confirmed it was the predator.It is on a blacklist of species that cannot be imported into the UK.There are fears it could have been smuggled in for an aquarium and then illegally released.Catching the vicious fish is considered great sport in Asia.
One of the world's leading angling guides, Jean Francois-Helias of Angling Adventures Thailand, has put his customers onto brilliant snakehead captures.
He told Angler's Mail: "That fish is a juvenile giant snakehead, or channa micropeltes, the meanest of all snakehead species.
"That giant snakehead has no fear. It even attacks human beings when protecting its fry."
The same fish caused chaos when they made it into the U.S. in 2002.
Snipers were set up on river banks to shoot them and entire lakes were poisoned in a bid to wipe them out.
Adult snakeheads can grow to 3ft and weigh as much as 44lb.