The Shannon Regional Fisheries Board has deployed extra fisheries officers to patrol the river banks between the Black Bridge at Plassey and Thomond Bridge.
Eamon Cusack, chief executive officer of the board, claimed thousands of salmon may have been taken from that part of the Shannon in recent years.
As part of new conservation measures, all fishing for wild salmon has been banned for the season on the Shannon, the Fergus and the Maigue.
The season started in March and finishes at the end of September.
Wild salmon fishing is being allowed on the Mulcair but a season quota of 1,200 is in place.
The board, owing to the activities of poachers, rejected appeals by anglers to open up the Shannon between the Black Bridge and Thomond Bridge.
Mr Cusack said the board, however, had agreed to allow coarse and brown trout fishing between the Black Bridge and Thomond Bridge. Ministerial approval is expected later this week.
Mr Cusack said: “The Shannon, between Plassey and Thomond Bridge, is one of the most poached stretches of the entire Shannon. As a result of this we have put in place extra fisheries officer patrols to address the situation there. From reports we have received, hundreds — if not thousands — of salmon have been illegally taken from this section of the Shannon.”
Mr Cusack said anglers could target hatchery or farm salmon between Plassey and O’Briens Bridge, adding that anglers could “identify hatchery salmon as they have their fins clipped”.
Mr Cusack said the conservation measures would yield long-term gains through increased salmon and white trout stocks on the river network.
Sean Quinlivan, spokes-man for the Limerick Anglers Association, said he welcomed the move by the fisheries board to restore coarse and brown trout fishing on the stretch.
But he added: “We want all kinds of angling opened up and I dispute the board’s claim that it is a poaching blackspot.”
He said up to 50% of its 300 members were juveniles.
“Many come from Moyross and, during the summer, angling keeps them off the streets.”
He said this helped deal with youth issues described in a report for the Government on Moyross and other parts of the city.