Like they said, put a trap out, try a cast net, maybe put a set line out, either a worm or minnow on the bottom. Patients is a vertue.
How long would you proffesionals wait until he takes further action if life isn't seen? Once the water hits 55* or 60*
What is your water temp now?
Could be you have fewer predators with enough forage so your fish aren't hungry? But not a total fish kill.... Good luck, keep us posted
