A 25-year battle to eradicate European carp from Tasmanian lakes is coming to an end, with less than 20 of the pest fish remaining.

The Inland Fisheries Service (IFS) believes Lake Sorell in the state's Central Highlands will be carp-free by next year, after a long and tedious eradication mission costing millions of dollars.

The fish was discovered in Lake Crescent in 1995 and in Lake Sorell a short time later.

It is a prolific breeder, with each female laying up to 1 million eggs, and the species degrades the habitat of native fish and has no natural predators.

IFS director John Diggle told Leon Compton on ABC Radio Hobart that it had been a "long war" against carp.

"We started a campaign of removal not sure if we could win or not."

Carp is a prolific breeder. ( ABC News: Cameron Atkins )

Mr Diggle said the carp had spread through the Murray-Darling Basin and caused major problems in waterways on the mainland.

"We had big concerns for the waterways here," he said.

"Our first response was to try and restrict them in the system."

A survey confirmed the carp invasion had been isolated to Lake Sorell and Lake Crescent.

Eradication was completed at Lake Crescent in 2007, but the task at the larger Lake Sorell proved more challenging.

'Spawning sabotage' successful

Mr Diggle said after last spring the carp count was at 50, and 39 more have been caught over that period.

Strategies including "spawning sabotage" and barrier netting have proved effective.

The 14-kilometre barrier net funnels carp looking for new breeding grounds into attached gill and fyke nets.

Chris Boon braves the cold to check nets at Lake Sorell. ( Supplied: Inland Fisheries Service )

Fisheries staff restrict the carp from its preferred spawning areas and also use containment screens to stop them spreading.

The fish have also been caught using "electro-fishing" that stuns them and through tracking devices.

Mr Diggle said the battle to catch and remove the final 20 would be tough.

"The closer you get to the end, the catch is finishing and you have to maintain a very high level of effort with catching very few carp," he said.

"The real challenge is to keep that level of intensity and effort up right until we can catch the last one."

It's been a huge and expensive task, which sometimes looked impossible to complete.

At one point, fish numbers were down to 50 but then there was another mass spawning, Mr Diggle said.

"It jumped back to thousands with a spawning event we couldn't stop."

About 60,000 carp have been eradicated through the program.

Jonah Yick and Storm Eastley have success stunning the fish in Lake Sorell. ( Supplied: Inland Fisheries Service )

Return to fishing getting closer

Lake Sorell is a world-class fishing spot but has been closed to recreational fishing since the carp was discovered, prevented by the eradication equipment in place.

Mr Diggle said anglers should be able to return next year.

"We're thinking it's a pretty good chance we will be able to do it at the tail end of the 2019-20 trout fishing season," he said.