For this lake it is more a problem of aquatic weed dieing off and using all the dissolved oxygen in the decomposition process., As a child I use to swim across the lake for fun and if I needed to rest the weeds would hold you up there are so many of them. The majority of the lake is very shallow so the amount of dissolved oxygen is limited to begin with. All of the ice fishing (or most of ) takes place in one smalls section of the lake around the only deeper basin.