Fisheries officers are confident they will declare Tasmania carp-free next year, boosting the state's reputation as a world-class trout fishery.

It has been a two-decade battle for the state's Inland Fisheries Service (IFS) to stop the carp wreaking the same havoc as they have in waterways interstate.

More than 40,000 carp have been eradicated from Lake Sorell in the Central Highlands, but the pest species has proved remarkably resilient.

Let's unpack some of the key questions when it comes to the "rabbit of the river".

Where have carp been living in the island state?

European Carp facts Native to central Asia

Native to central Asia Introduced into Australian waterways more than 100 years ago

Introduced into Australian waterways more than 100 years ago Adult fish have no natural predators

Adult fish have no natural predators Known to degrade habitat of native fish

Known to degrade habitat of native fish Adapts to conditions including low-oxygen and brackish water

Carp were actually first discovered in the state's north-west in 1975 and again in 1980 and were destroyed with the fish poison rotenone.

But the real battle started when they were found in the neighbouring Central Highlands lakes — Lake Crescent and Lake Sorell in 1995.

Lake Crescent was cleared of carp in 2008 and the job is almost done at Lake Sorell, with hope it will be opened back up to anglers in 2018.

Why has it taken 20 years?

Female carp in a net after receiving pheromone implants at Lake Sorell in Tasmania. ( ABC News )

When it comes to survival of the fittest, carp are king.

They are ferocious breeders, with each female laying up to 1 million eggs. Apart from fisheries workers, the adults have no natural predators.

In the past decade the IFS thought it was close to clearing Lake Sorell, but all it took was a few spawning females and the numbers shot back into the thousands.

Carp researcher Jawahar Patil in the lab. ( ABC News: Ted O'Connor )

University of Tasmania researcher Jawahar Patil has studied carp for decades and said the pest species was much smarter than most fish.

"They learn to evade capture," Dr Patil said.

"If they get used to a particular fishing method they learn to avoid it pretty quickly."

Carp are also much hardier than native fish and are not fussed by poor water quality or a drop in oxygen levels.

What's been the breakthrough?

Fisheries officers like Chris Wisniewski, who has been tackling carp for most of his career, said there had been no one silver bullet.

Chris Wisniewski from Inland Fisheries catching carp in a fyke net. ( ABC News: Ted O'Connor )

He said the battle had been more like "trench warfare".

"The indication is they haven't spawned for the last couple of years is probably because we've been fishing the big fish out as they come in, so our techniques are working," he said.

But one key advantage has been the ability to radio-track the carp to see where they move, in particular where they spawn.

In Mr Wisniewski's words "to think like a carp".

This data allows the team to set up net traps in the best locations.

A carp caught in Tasmanian lake with tracking device attached. ( ABC News: Ted O'Connor )

Another trailblazing technique is to use females pumped full of pheromones to attract the males into the nets.

This winter has thrown up another challenge.

The lake's water level has risen to make available new spawning locations.

So fisheries workers put up a 14-kilometre barrier net, which funnels carp looking for those new fertile breeding grounds into attached gill and fyke nets.

Why go to all this effort?

The Tasmanian Government has spent about $10 million on eradicating carp in the past two decades.

The Federal Government has supported carp eradication in Tasmania since 2011 with $2.1 million.

Tasmanian Fisherman Ken Orr is keen to see the carp gone. ( ABC News: Ted O'Connor )

Trout fishing is one of the state's biggest tourist drawcards and Lake Sorell used to be a prized location and a hive of activity in summer, but since carp were discovered it has been closed.

Local fisherman Ken Orr Junior is one of many anglers keen to see it return to its former glory.

"It was one of the world's best fisheries and that has stopped," he said.

"My grandfather fished here, my father fished here, I fished here, but my kids who are in their 20s now haven't fished here."

Tasmania is also desperate to avoid the infestations seen in New Zealand and the US and even closer to home where millions of carp have decimated habitats in the Murray-Darling system.

Dr Patil said fishing bodies abroad were looking to Tasmania's success for inspiration.

"Tasmania has almost been a trailblazer in terms of developing new technologies and adopting new technologies," he said.