A Better Bite Begins

We are getting very close to that time of year when the bite for most species really turns on.  I know many people have been complaining this ice season about the tough bite in many parts of the Midwest.  The reason for the tough bite in many parts of the Midwest is simply we had a lot of snow cover this year.  Not only did we get a lot of early snow, but the snow covered stuck around until recently which has significantly impacted the bite on many lakes.  In addition, the snow made lake travel tough as for much of the typically good fishing time early ice we had a lot of slush to deal with.  But, essentially the tough bite can be attributed to low Dissolved Oxygen levels in many lakes across the Midwest.

The air we breath as humans is 21 percent oxygen.  Obviously, fish need oxygen also and the oxygen in the water available to them is called dissolved oxygen.  Fish use their gills to extract oxygen from water just as we use out lungs to extract oxygen from the air.  Most fish do well when dissolved oxygen levels are 5 parts per million or higher.  When dissolved oxygen is less than 5 ppm they become uncomfortable and their normal patters will change.  Most fish will begin to suffocate and die when dissolved oxygen levels are at 2 ppm or less.  Depending on the length of time dissolved oxygen levels are low, you can end up with either a full winter kill or a partial winter kill.

Dissolved Oxygen levels in lakes are significantly effected by the amount of light penetration.  Snow cover on ice significantly decreases the amount of light penetration under the ice.  A 1961 study by Mackenthun and McNabb found that less than 1 % of light passed through 16 inches of ice covered by 2 inches of snow.  Without light, plants die instead of producing dissolved oxygen through photosynthesis and to make matters worse, oxygen is used through the process of decomposition further complicating the problem.

In the presence of low dissolved oxygen levels in lakes it is common for fish to become lethargic.   Fish will move less during the day and in most cases feed less.  As a result of these circumstances fish from these lakes grow slower also.  As anglers we notice this behavior when we fish a lake that the fish won't bite during the day or only for a short window in the morning or evening.   In addition, when oxygen levels are extremely low, the bite may be nonexistent.

The good news now is that for much of the Midwest the snow is gone or almost gone.  Many lakes that were at or near partial winter kill levels are benefiting from the recent thaw that took place.  The increased light penetration should benefit most of our lakes and save a few.  In addition, we are very near runoff season which will reoxygenate most of our lakes albeit they are still ice covered.  So, don't give up on the season, you may be missing the best bite of the year.