The Kalang River was closed for harvesting after a virus was discovered in local oysters.
Oyster growers fear the decision will cost them hundreds of thousands of dollars.
But John Williams from the DPI says closing the river was the only option.
"You can't compromise product safety and integrity for any good reason," he said.
"What we would hope to do is that we might be able to identify that there's only a small portion of the river that's suffering this problem.
"We might be able to ...
