YP are much more tolerant of low DO compared to bass, especially SMB. The winterkill could have easily removed all your LMB from the fishery. If any survived they would be the smallest ones. Biggest ones die 1st in uniform concentrations of DO shortages.
We have aeration year round in the ponds, so DO was not the cause. Plus the Bass died in early May, while ice-out was at the end of March. I have a lot of background in fish health and couldn't pinpoint any acute infections or other environmental causes...but they all had pretty severe Columnaris growth, ulcers, and whatever else.
They were all dead when I found them, so trying to culture them would not really help diagnose a specific cause of death. I walked around a couple times a day for 2 weeks, hoping to spot one that was still alive, but sick enough to net out....never happened.
All I know is that no one had ever caught a LMB in this pond (mostly for a lack of fishing for them), then these 8 monsters showed up dead and I haven't seen any LMB since.
Who knows?
Be careful of only using ice fishing to evaluate the YP density. Generally the larger YP are most the easiest ones to catch when ice fishing. Set some minnow or slightly larger small fish traps to better assess the size structure of the subadult YP numbers. Or do some angling that targets small fish; small hooks(#8-10), a small float and worms fished 3-4ft deep. This method will give you good evaluation of the YP population.
If I had boat access to this pond, I would have set fyke nets in 2016 and run a series of mark-recapture sets....but I'll have to look into traps or maybe make some smaller trap nets of some kind?
Any leads on small fyke nets that could be set with an electric trolling motor on a little 10' john boat?
