Page 12 - Crappie NOW - September 2017

TACKLING TURNOVER TO CATCH FALL CRAPPIE

He relies on a 3/8-ounce weight for both
his drop shot and slow trolling rigs.
The fall turnover can be a frustrating
time to fish for crappie, but it usually only
lasts for a week or two and then the fishing
improves dramatically because the water
temperature and dissolved oxygen levels
are consistent at a wide range of depths.

- John Neporadny Jr.

How a Lake Turns Over
One of the best explanations of the fall turnover that I have found
was in the Missouri Department of Conservation (MDC) Aquaguide,
which has a chapter on Pond Turnover. The same description of
turnover that the MDC uses in this chapter can also be applied to
larger lakes and reservoirs.
According to the MDC, lakes stratify during the summer into three
layers of water with different temperatures, densities and dissolved
oxygen levels. The layers do not mix because of these differing
properties. Composed of warm, lighter water, the upper level is known
as the epilimnion. The middle layer of water known as the thermocline
is a transitional level where water temperature drops at least 0.5
degrees for each foot of increasing depth. It is also a transitional layer
of dissolved oxygen levels. The lowest layer known as the hypolimnion
has the coolest and densest water of the three zones.
The MDC notes as the air temperatures drop toward 50 degrees
in the fall, the epilimnion cools and becomes more dense and heavier,
which triggers the turnover process. The cooler, dense water sinks and
autumn winds stir the epilimnion and causes the thermocline to erode.
Eventually the waters become uniform in density and temperature
leading to the complete mixing of the water column known as fall
turnover. The mixing can occur overnight and leads to changes in the
color and smell of the water. The changes are caused by the circulation
of decaying particles of organic matter and gasses that accumulated in
the hypolimnion throughout the summer.

12 Crappie NOW September 2017