hey micro,
I was thinking about fishing wallum and i remembered talking to a state biologist out there years ago...he was checking oxygen levels at various depths late in the season. he told me to fish at a certain level where the oxygen level was the highest.
at wallum because there is little stream fed water, oxygen levels fall late in the season. the lake relies on wind action to oxygenate the water and the longer the ice cover remains the lower the oxygen levels get. also the levels tend to stratify in layers a various depths and the fish tend to stay in the higher oxygenated layers..so try to vary your depths perhaps.
cya on the cold ice
Steve