Operations at Bunratty Castle are included in the shake up in Shannon tourism.
Five top managers are leaving the Shannon Heritage subsidiary of Shannon Development which operates the Castle Banquets and other visitor attractions.
Changes in the flagship State tourism operation that handles almost 750,000 visitors to the Shannon region each year are taking place in advance of changes at the top.
A new chief operating officer at Shannon Heritage Mr John Ruddle who is moving from the National Trust of Northern Ireland where he was financial controller and deputy director is to take up the post in September.
It is 40 years since Bunratty Castle in County Clare was launched as a medieval banquet venue.
Mr John King, Director of Heritage and Tourism with Shannon Development said the changes are a business recovery plan and "have been necessary to stabilise the company in a difficult trading environment".
His circular to staff added that the recovery plan was geared to deal with issues following a very difficult trading year for tourism in 2001 and the ongoing difficult trading situation in 2002.
For the first time since the 1960s banquets at Buntratty's sister castles of Knappogue in Quin and in Dunguaire on the Clare/Galway border are operating this year on a five nights a week basis.
Shannon Heritage introduced contract entertainment last year with performers for the Shannon Ceili at Bunratty Folk Park being hired in from a private operation and in other privatisation moves the banquet and ceili catering at Bunratty and Knappogue moved away from State management under Aer Rianta Shannon for the first time in 40 years.
The Castle Catering contract was won under tender by Masterchef and its new Shannon Hospitality subsidiary has also taken over management of two pubs, Mac's in Bunratty Folk Park and the Castle Lane Tavern beside King John's Castle in Limerick.
Under a voluntary early retirement package three senior managers and two middle management have opted to go.