Salmon numbers to be cut in Tas harbour

Tasmania's environmental watchdog will slash the number of salmon being farmed in the Macquarie Harbour over the summer.

Concerns over oxygen levels in the harbour has prompted the Environmental Protection Authority to take the action.

The state government backs the move.

In a statement on Wednesday, Tassal chief executive Mark Ryan said the decrease "would not have a material impact" on the company's ability to supply salmon.

The EPA has written to producers warning them of the planned action over summer, giving them four weeks to respond.