The Liberal Member for Narracan, Gary Blackwood, says he will call on the Water Minister to review the management of the Horseshoe Bend on the Thomson River.
Currently most of the river flows through the heritage-listed Horseshoe Bend tunnel, which was built by miners last century.
But a consultant's report commissioned by the West Gippsland Catchment Management Authority recommends building a new channel to return water around the bend and allow fish migration.
The Friends of the Horseshoe Bend Tunnel say the plan would threaten the future of the tunnel as a tourism destination and have outlined plans for a smaller water diversion project.
Mr Blackwood says he has met the group and shares its concerns.
"I would be certainly keen just to ask him to stop the process for the time being and get himself a chance to become familiar with it and really have a good look at the science at both sides of the debate and also more importantly, I think, look at the heritage significance of the Horseshoe Bend tunnel," he said.
Environment Victoria says it is satisfied the consultant's proposal would deliver increased flows and promote fish migration around the Horseshoe Bend.
The group's health rivers campaigner, Juliet LeFeuvre, says there is a good reason why there are not many grayling trying to migrate in the area.
"Well I think … it's a bit of a chicken and egg thing, are there few grayling because they're at a dead end and they can get anywhere," she said.
"I mean one of the things the consultants did was check throughout the broader catchment and see where they could get the best benefit or bang for buck for the grayling and they've come to conclude that the Thomson is the most suitable habitat that there is around."