Shellfish farms on a Cornish river may have to close permanently if the water quality is not improved.
A multi-agency approach will now be used to improve quality
The warning has come from Truro's harbour master, Andy Brigden, who says pollution at King Harry Reach near Feock is getting worse.
The water quality was downgraded last year after bacteria was found in the Fal Estuary and a study found possible sewage discharge in some areas.
Mr Brigden said if action was not taken soon, jobs would be lost.
Last year's downgrading led to seasonal bans of shellfish harvesting, unless the crop had been re-laid in clean waters for a period of up to three months.
Carrick Harbours Board has now been asked to work closely with the Port Authority and the Environment Agency to tackle the problem.