Millions of giant Pacific crabs, whose ancestors were brought to Europe by Joseph Stalin in the 1930s, are marching south along Norway's coast, devouring everything in their path.

The monster crabs, which can weigh up to 25lb and have a claw-span of more than three feet, are proving so resilient that scientists fear they could end up as far south as Gibraltar.

Energised by a mysterious population explosion a decade ago, whole armies of the crustaceans - known as the Kamchatka or Red King Crabs - have already advanced about 400 miles along the roof of Europe, overwhelming the ports of northern Norway.

They now number more than 10 million and have reached the Lofoten Islands off north-west Scandinavia, leaving in their wake what one expert described as "an underwater desert".

In a graphic display of the extent of the crab's submarine domination, some photographs of the ocean floor in Kirkenes in northern Norway show a writhing mass of the ugly, spiny animals.

Northern clams and other shellfish, once so numerous that divers could scoop up handfuls, have been all but eliminated.

Lars Petter Oie, a Norwegian diver who lives nearby, has seen the fjord outside his front door taken over by the crabs.

Plunging through a hole in the ice, another diver surfaced within two minutes with a huge specimen. A snap of its claw is enough to remove a man's finger.

Mr Oie said: "I have been to conferences on the crab and one thing the experts agree on is that they have rarely come across a species that is so adaptable.

"It can survive on almost anything: kelp, dead fish, seaweed and fish eggs. It even eats crushed shells to get the calcium it needs for its shell."

The relentless advance of the crabs has led to calls from some Norwegian marine experts for a government-subsidised "blitz" to try to halt their relentless march south.

Andreas Tveteraas, an analyst in Oslo with the international World Wildlife Fund, said that urgent steps needed to be taken.

"This animal has no natural predators and it's an alien species in the Barents Sea. That's why its numbers are exploding.

"Some scientists say it will stay in the north because it likes the temperature but others think it can go as far south as Gibraltar."

For years the Norwegian government has ignored the underwater advance, undecided whether to treat the crabs as a resource or a pest.

The animal's legs are considered a delicacy and fetch top dollar in Japan and America. Even in Oslo, consumers pay around 200 Norwegian kronor (£15) a pound.

Served with bread, butter, lemon and mayonnaise, the taste and texture of the crab meat is comparable with that of the finest lobster.

At present, some Norwegian fishermen have been granted seasonal licences to catch the Kamchatka crab but stiff regulations on the size of the boat used and other criteria mean they are few in number.

Aasmund Bjordal, of the Department of Marine Resources in the western Norwegian town of Bergen, said: "We're between two policies. One is to get rid of the crabs. The other is to manage it as a fishing resource.

"In the meantime, it's already become an important source of income for some fishermen in the north. The problem is that it may be destroying the fishing stock."

Predicting the crab's long-term effect on the marine ecology is difficult. The Barents Sea provides some of the world's richest fishing grounds and a collapse in stock would be a major disaster.

There is some evidence that the crabs, which often live at great depths, have been eating the eggs of the caplin, a small fish that is a main source of food for cod.

In its native Pacific it faces much sterner competition but has nevertheless edged out other bottom-feeders to reach northern Japan and Vancouver Island.

Transporting the monster crabs to the Barents Sea was originally part of a Stalinist era scheme to provide food for the populations in the north-western Soviet Union.

In recognition of the growing threat to the local ecology, Norwegian authorities finally lifted on Jan 1 some of the restrictions on crabbing along part of the shoreline.

Many Norwegian fishermen hate the crabs, blaming them for falling fish stocks and complaining that they get tangled in their nets. But for others, they have brought unprecedented wealth. At the Rallarn, a pub near the harbour, a fierce debate raged this week. Some favour annihilating the crabs, an almost impossible task, while others are tickled pink at the chance to gorge for free on a rare delicacy they find almost at the bottom of their gardens.

Elvis Jenssen, 41, said: "The bloody things hoover up everything off the bottom of the sea and all the fish are disappearing. They came over from Russia and now they're taking over."

But Glenn, a 30-year-old car mechanic, replied: "It's true the seabed now looks like the Sahara but they certainly taste good."

We'd better review the rules:

Horror Movie Survival Guide

When it appears that you have killed the monster, never check to see if it's really dead.
If you find that your house is built upon or near a cemetery, was once a church that was used for black masses, had previous inhabitants who went mad or committed suicide or died in some horrible fashion, or had inhabitants who performed necrophilia or satanic practices in your house move away immediately.
Never read a book of demon summoning aloud, even as a joke.
Do not search the basement, especially if the power has just gone out.
If your children speak to you in Latin or any other language which they should not know, or if they speak to you using a voice which is other than their own, shoot them immediately. It will save you a lot of grief in the long run. NOTE: It will probably take several rounds to kill them, so be prepared.
When you have the benefit of numbers, never pair off and go it alone.
As a general rule, don't solve puzzles that open portals to Hell.
Never stand in, on, above, below, beside, or anywhere near a grave, tomb, crypt, mausoleum, or other house of the dead.
If you're searching for something which caused a noise and find out that it's just the cat, leave the room immediately if you value your life.
If appliances start operating by themselves, move out.
Do not take anything from the dead.
If you find a town which looks deserted, it's probably for a reason. Take the hint and stay away.
Don't fool with recombinant DNA technology unless you're sure you know what you are doing.
If you're running from the monster, expect to trip or fall down at least twice, more if you are of the female persuasion. Also note that, despite the fact that you are running and the monster is merely shambling along, it's still moving fast enough to catch up with you.
If your companions suddenly begin to exhibit uncharacteristic behavior such as hissing, fascination for blood, glowing eyes, increasing hairiness, and so on, get away from them as fast as possible.
Stay away from certain geographical locations, some of which are listed here: Amityville, Elm Street, Transylvania, Nilbog (God help you if you recognize this one), the Bermuda Triangle, or any small town in Maine.
Never, ever, ever turn off the paved road onto a gravel or dirt road.
Always make sure that your car has a fresh battery so it will start immediately in times of crisis.
If your car runs out of gas at night, do not go to the nearby deserted-looking house to phone for help.
Beware of strangers bearing tools such as chainsaws, staple guns, hedge trimmers, electric carving knives, combines, lawnmowers, butane torches, soldering irons, band saws, or any device made from deceased companions.
Do not keep all your sharpened kitchen knives in one of those wooden block thingies on your worksurface.
When you're searching a house because you think there's something dangerous there, for goodness sake turn the bloody lights on!
Never back out of one room into another without looking. It's always behind you.
If anything other than water (blood, thick goo of any color) comes out of a faucet, do not call a plumber. Leave the house immediately.
If, looking in a mirror, you see a figure behind you that you don't see upon turning around, you see a different room than the one you are in, you see a figure other than yourself looking back, or your reflection tells you to get out before it is too late, proceed to the nearest exit with all speed.
If you open a door and the room you see is not the room that should be there, do not explore it. In fact, even if you close the door and see the correct room after re-opening it, vacate the house.
Never say that you'll be right back because you won't.
Listen closely to the soundtrack; and pay attention to the audience, since they are usually far more intelligent than you could ever hope to be.
And finally, never drink, do drugs, or have sex. Because only virgins survive in the end.

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