The Dreaded Thermocline
The hot dog days of summer also bring a very strange phenomenon known as the thermocline. This often-misunderstood natural event has many descriptions of what it actually is, why it occurs and best techniques to deal with it. 🤔
Webster Dictionary says this:
thermocline noun ther·mo·cline | \ ˈthər-mə-ˌklīn \
Definition of thermocline
: the region in a thermally stratified body of water which separates warmer surface water from cold deep water and in which temperature decreases rapidly with depth
What it is in regular fishing language is a relatively thin layer of water lying in between the warm
epilimnion and cool hypolimnion, and in this region the water temperature drops rapidly
with every foot of increasing depth. Generally speaking, the lower layer also has drastically reduced oxygen content so even though fish may prefer the cooler temperatures over the hot surface water they can’t survive there for any length of time.
This event can be literally seen and felt. Most modern depth finders can clearly define the actual layer by manually setting a very high sensitivity setting. On normal settings if you spend some mapping time you will begin to notice a depth pattern of baitfish and game fish.
Thermoclines can be shallow as well as deep depending on the depth of water and clarity. If you have ever swam down in a pond or lake at the right depth during the summer, you have most likely hit a sudden cold-water layer. If you are like me that first experience probably scared, you the first time.
Since we know that the bait and game fish cannot live below the thermocline for extended periods of time, we must adapt our locations and presentations to provide a better chance of catching our target species.
Vertical presentations seem to be more productive for suspended fish during this time. White jigs, grubs and soft plastics that simulate a shad may be preferred choices. But always keep in mind that the thermoclines can be much shallower than you would think. In certain cases, topwater can prove deadly under the right conditions.
All in all the dreaded thermocline is pretty much a given late summer however with a little work it doesn’t have to be a bad day on the water.
Be sure to check back in next Tuesday for more tips from our expert staff and pro staff from around the country.