Eagle MagnaView Installation And Operation Instructions Manual page 23

Most fish don't spawn unless the water temperature is within rather
narrow limits. The surface temperature meter built into the Magna Plus
helps identify the desired surface water spawning temperatures for vari-
ous species. Trout can't survive in streams that get too warm. Bass and
other fish eventually die out when stocked in lakes that remain too cold
during the summer. While some fish have a wider temperature toler-
ance than others, each has a certain range within which it tries to stay.
Schooling fish suspended over deep water lie at the level that provides
this temperature. We assume they are the most comfortable here.
The temperature of water in the lake is seldom constant from top to
bottom. Layers of different temperatures form, and the junction of a
warm and cool layer of water is called a thermocline. The depth and
thickness of the thermocline can vary with the season or time of day. In
deep lakes there may be two or more at different depths. Thermoclines
are important to fishermen because they are areas where fish are active.
Many times bait fish will be above the thermocline while larger game fish
will suspend in or just below it.
The MagnaView can detect this invisible layer in the water, but Fish ID
will have to be off, and the sensitivity will probably have to be turned up
to see it.
SURFACE LAYER
ABSORBS HEAT
FROM THE SUN
EPILIMNION
THERMOCLINE
MOST PRODUCTIVE
ZONE FOR FISHING
HYPOLIMNION
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