<< . One called Silver Lake, it
was so warm at the surface it tired you out if you tried to swim hard swim in
it. I used to float around among the shallow water plants for hours some
times.
Large mouth bass would swim under my chest and sit there in the shade and I
could feel his dorsal fin waving against my chest. But if you went down about
10
feet the there was a thermocline you could see and when you swam onto it felt
like ice water. >>
I do a lot of deep water fishing for Smallmouth Bass, Lake Trout, Northern
Pike and Walleyes. I measure the temperature at different depths and it is a
pretty constant gradient as you get below the top six inches or so. In late
summer the thermocline gets established in the deeper parts of the lake
(thermocline is where the temperature gradient becomes very much steeper in its change).
There are usually no Lake Trout below the thermocline because the oxygen level
is much lower. I also have felt the cooler water as I snorkel (in Canada, the
surface warm layer feels very pleasant at about 75 degrees). Even in my
garden below ground lily ponds I can feel the cool water at the bottom. In fact,
water lilies do not thrive when the temperature gradient is disturbed by water
circulating pumps or vigorous aeration. So, I guess what I am saying, a water
gradient is natural and desirable in a pond or an aquarium. Now, on the other
hand, river fish do not experience that same gradient, except, as you point
out, in caves or crevices or backwaters.
Lee Harper
Media, PA
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