Staff from the Department of Primary Industries have released 1000 trout into Wentworth Falls Lake to combat redfin

Staff from the NSW Department of Primary Industries have released 1000 trout into Wentworth Falls Lake as part of the annual fish restocking program.

Don Barton, secretary of the Central Acclimatisation Society, said the trout were much larger than those released in previous years - 230 mm long, instead of the 100mm fingerlings - to combat the "big problem" of "noxious fish".

The larger fish, paid for by NSW recreational fishing fees were necessary to withstand the impact of the "big problem" of the highly piscivorous redfin (English Perch), a noxious fish which had been illegally released into the Lake some years ago, he said.

The Lake fish release occurred on Wednesday January 12 - they had travelled from the Gaden Trout Hatchery at Jindabyne.

"People need to be mindful of the environmental damage that can be caused by dumping unwanted aquarium specimens, domestic ducks and even garden waste," Mr Barton said.

"In the case of redfin, the action is more than careless, it is an act of criminal arrogance, committed by people who are too inept or lazy to pursue more challenging fish to catch, such as trout and Australian Bass which are present in the Lake.

"Local anglers should be able to enjoy good sport in pursuit of the trout in the near future. Unlike redfin, neither the trout nor bass can reproduce in the Lake but future releases will maintain the numbers."

Trout need to be able to run up into running water and make nests to lay their eggs in coarse gravelly stream beds and bass need to go down to salt water to breed.

Adults need a fishing licence to fish and most of the trout will need another six weeks to grow to an allowable size of 250 mm. A recreational licence costs $35 annually and can be bought online through the DPI or at tackle shops, where anglers can check bag limits (at Wentworth Falls it is five) and sizing.

He said there were still plenty of large trout in the lake which have survived previous fish stockings.

And anglers were encouraged to "catch and kill as many redfin as possible, as this will improve the size of catchable fish".

"Redfin breed rapidly, overpopulate the water body and exhaust the food resource, resulting in a myriad of stunted fish of no use to anyone," he added.

He jokingly said it was a "state secret" the locations at the lake where the trout were released, but added some children had spotted the release "and were coming back next week to fish".