Agriculture Minister Adam Marshall made the announcement on Wednesday, with the bag limit coming into force on October 14.

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The news comes just days after a Sydney man was caught at Lake Illawarra over weekend allegedly in possession of 1200 cockles.

"I asked the Recreational Fishing Advisory Committee to consider the current bag limit and advise me on its appropriateness as a matter of priority," Mr Marshal said.

"It is based upon their recommendation that the procession limit has been reduced from 50 to 20.

"This reduction in bag limits is a timely response to an issue that has caused concern along our coastal communities, particularly in the Illawarra,"

Kiama MP Gareth Ward said he had spoken with Mr Marshall about reducing the bag limit for cockles, because overfishing of the species at Lake Illawarra has become a problem.

"I've been really disappointed how some people have been out and out greedy," Mr Ward said.,

"The experience has been that it's from people outside the region mainly, most locals have done the right thing.

"We need to make sure they are appropriate bag limits so the species can be there for everybody to enjoy and share and also so it can do the important work that it does as part of the ecosystem and the ecology of the waterway."

A 20-cockle limit had been put forward by Shellharbour City councillor Peter Moran last month, while Shellharbour MP Anna Watson had called for a two-year moratorium.

Resident John Davey has started an online petition, also calling for a moratorium.

Mr Ward was opposed to a moratorium, stating it wouldn't work.

"Calling for a moratorium is short-sighted," he said.

"I don't think that would receive the support of local fishers because in the main it's the local fishers who do the right thing. It's people outside our community who have been the ones causing havoc."

Mr Ward said he had also spoken to the minister about the need to increase enforcement of the 20-cockle limit.

"There's no point having bag limits unless they're supported by additional enforcement and he said he would consider that," Mr Ward said.

Ms Watson also said what was needed now was "boots on the ground".

"People who are illegally harvesting more than 1200 cockles are not going to stop just because the limit has been reduced from 50 to 20," she said.

"We need a proper education campaign about the limits, and we need Department of Primary Industry officers enforcing them."

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