This lake used to be one of the best trout fisheries in Australia... I just spent 4 days there trolling, downrigging, fly fishing, bait fishing and throwing soft plastics and only managed two tiny rainbows. I could see the fish 160ft down in the old Snowy Mountain River bed on the sounder, but there was nothing in the shallower bays. Any ideas?

Yep...Ideas but no real answer.

I measured 1c at 7am in Paynesville (about an hour ago). Very cold for this time of year. In fact that would be very cold for this part of the country in the midst of winter !! Paynesville is not far from the Snowy's. Maybe this unusually cold weather has affected them.

Maybe something has scared them into deeper water. Or maybe something has polluted the surface water.

Or maybe they are sick...Trout are an introduced species. Not being in their native location, they might have encounted a native pathogen that they cannot cope with.