LANSING, Mich. — The director of Michigan’s Department of Environmental Quality is delaying a decision on whether a fish farming operation can substantially boost production of rainbow trout on the Au Sable River.

Heidi Grether wants an administrative law judge to reconsider whether Harrietta Hills Trout Farm should have to monitor fish for whirling disease under a permit that would let the company gradually raise output to 300,000 pounds annually at its facility in Grayling, up from 20,000 pounds a few years ago.

Groups opposing the expansion say farm-raised fish could expose wild trout downstream to the deadly sickness.

Administrative Judge Daniel Pelter recommended granting the permit in February and said the DEQ doesn’t have authority to require such monitoring.

But Grether disagreed in a recent order. She told Pelter to take another look and said she’ll make a final ruling on the permit afterward.