Popular Rosebery Reservoir was due to re-open for the season on Saturday, August 1, after essential work by Scottish Water.
The 52-acre water near Carrington in Midlothian was sold-out for opening day but Dave Picken, the fishery manager, said things changed on Thursday.
He added: “We have had to cancel the start of fishing as the water level dropped again. It made it too dangerous with soft mud and slippery rocks. We are now aiming for 15th, either giving it time to dry out or two weeks of rain.”
The fishery caters for fly fishermen and has two areas for bait fishing. Anglers of all ages and abilities are welcome