Nine years ago near the central Darwin boat ramp, a saltwater crocodile locked its jaws around veteran ranger Tom Nichols' hand, spun around and tore off two of his fingers.

A larger crocodile would have taken his arm at the shoulder.

The Northern Territory has the world's busiest and most sophisticated crocodile management program, regularly hauling about 250 of the ancient reptiles from Darwin harbour each year.

NT crocodile rangers haul a 2.5-metre saltwater croc trapped in Darwin harbour. ( ABC News: James Purtill )

A team of five rangers checks 26 permanent croc traps dotted about the harbour, as well as many small creeks and mangrove estuaries.

Smaller ranger crews trap crocodiles in the Adelaide River near Katherine as well as the Litchfield National Park. Nowhere else in Australia are crocodiles controlled on such a scale.

Drawing pins indicate the locations of the Problem Crocodile Management team's permanent and temporary baited traps in Darwin. ( ABC News: James Purtill )

"All we're doing is we're creating a vacuum," Mr Nichols shouted above the roar of the outboard, motoring to a permanent floating trap 18 kilometres from Darwin's foreshore.

"If there was no trapping program the number of crocodiles in the harbour would be extra high.

"There would be more fatalities and more risk for recreational users."

But he said he was against culling.

"It would just create a false sense of security," he said.

NT Problem Crocodile Management wildlife officer Tom Nichols motoring to a crocodile trap on Darwin Harbour. ( ABC News: James Purtill )

Since the NT banned crocodile hunting in 1971, estimated croc numbers rebounded then boomed to more than 100,000.

Over the same period, the human population of the Territory almost tripled to about 230,000.

The men and women of Problem Crocodile Management have created a buffer between the two apex predators and their habitats - between the wild waterways and the city, towns and suburbs.

In the wet season creeks rise and crocodiles slip out of the rivers and ocean to infiltrate places of human settlement.

The croc team are on 24-hour standby, responding to sightings phoned in by residents.

The boat motored passed a natural gas tanker berthed near Wickham Point in the middle of the harbour.

With the Territory's gas boom, the team are advising resource companies to assess crocodile risk.

The team have also begun meeting counterparts in Queensland and Western Australia where crocodiles are being sighted further south.

To illustrate the danger, before the morning boat trip news broke that a crocodile may have taken a man on Melville Island in the eastern Timor Sea, just north of Darwin.

Mr Nichols was due to fly out to the island in the afternoon, taking with him gear including harpoons, ropes, gaffer tape, a .308 calibre rifle and a shotgun.

There is more than one way to catch a croc.

"They're certainly not dumb," Mr Nichols said.

"They're like humans. You never know what they are capable of. And every year there's one croc with a mongrel eye."

The boat slowed down as it approached the croc trap moored near mangroves. Inside swims a croc about half the length of its 5-metre-long half-submerged aluminium cage.

For crocs trapped like this, the NT catchers have developed their own method, using a winch and cable-ties which they say is safest for both the catcher and the croc.

Did they ever jump on the back of a croc like Steve Irwin?

"We don't do that," Mr Nichols said, spinning the boat's wheel with his maimed hand.

Standing on the floating trap, wildlife officer Emma Jackson prepares a noose to fasten about the crocodile's upper jaw. ( ABC News: James Purtill )

Fellow wildlife officer Emma Jackson stepped out of the boat and stood on the cage, tying a nylon rope into a lasso and lowering it through an aperture to fasten it around the animal's upper jaw.

She tapped its snout with a stick to make it open its mouth.

With its mouth fastened shut with a plastic cable tie, the 2.5 metres saltwater crocodile is guided out of the trap. ( ABC News: James Purtill )

Using the rope like a dog lead, she walked the crocodile out of the cage and around the side of the boat.

She then ran the rope through a winch and hauled the crocodile up.

As its jaw poked over the gunwale Tom Nichols fastened a standard plastic cable tie to clamp its mouth shut.

After the crocodile has been winched up the boat's side its jaws are fastened shut with a cable tie. ( ABC News: James Purtill )

The crocodile was then lowered back into the water, walked to the back of the boat and hauled up a purpose-built slipway and laid bow-to-stern on the deck.

Ms Jackson gaffer-taped a hessian bag over its eyes and taped its powerful hind legs together.

In just five minutes the dangerous animal had been transferred from the trap to the bottom of the boat, where it lay hooded and immobile.

With a strip of hessian sack taped over its eyes, the crocodile lies immobile on the floor of the boat for the journey back across Darwin harbour. ( ABC News: James Purtill )

The trap was then re-baited with feral pig meat.

The team goes through 80 kilograms of the meat each week.

A slab of feral pig meat is lowered into the crocodile trap as bait. ( ABC News: James Purtill )

The pair motored back to the boat ramp, winched the boat onto the trailer, and drove to headquarters in Yarrawonga near Palmerston on the outskirts of Darwin.

Passing motorists had no idea there was a crocodile in the boat.

At headquarters, the animal measured 2.5 metres tip-to-tail - small compared to the five-metre ''monster crocs" they had pulled from the harbour and Top End rivers.

Wildlife officers measure the animal's length before it is taken to a crocodile farm. ( ABC News: James Purtill )

It will be sold to a crocodile farm for a nominal fee.

"They do what they want to do with them," Mr Nichols said.

The crocodile is carried from the boat to a caged ute for transfer to a crocodile farm. ( ABC News: James Purtill )

The largest and most impressive crocodiles are sold for five-figure sums to overseas zoos and reptile parks.

Females may be kept as breeding stock, but this male, which about 24 hours ago was living freely in the open ocean, would probably be killed and skinned for handbag and shoe leather.