Bluegill - Big Bluegill

Do you love big bluegill?

Just thought I’d share one of my trophy/Lunker presentations for the hot summer periods. Its fishing the thermocline break with the drop shot.


At most periods or times of the year big fish have access to the whole area of the lake shallow or the deepest region. When the thermocline develops during the hottest part of the year the summer period a barrier develops at the thermocline where the oxygenated layer separates from the coolest layer at the deeper areas of the lake. The thermocline break is the intersection of the lake bottom and the thermocline depth. Fish that line and you have an increased chance of finding fish concentrations and the hawgs that have been moved up from the deeper regions


In my local area many lakes develop a thermocline separation at 16-18 ft during the summer period. Remarkably this concentrates (depending on the lake) all fish to the shallower areas for easier angling access. Here is a screen dump of a lake with shallower areas less than 17 foot are in dark blue. A huge decrease in searchable fishable water!. Most fish will relate to the bottom rather than suspending in deeper water above the thermocline at this time.


So the the work of finding fish was just made easier by that thermocline.


To find this thermocline with a sounder turn up the sensitivity and a distinct line will show up at that level of separation.


I use drop shot and vertical ice jigs at this time. Fish close to the bottom and you will find this spectrum of fish.

A recent catch at the thermocline break in 15 ft of water.


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Replies to This Discussion

Simple explanation of a quasi-complex subject.
I especially like your breakdown of the "intersection"

All I need now is something more mobile than a float tube!

thanks David! very nice coming from a seasoned angler such as yourself!

its just something to think about when we anglers are out on the lake and fish are tough to find in the shallows or are usual spots. there is always that barrier out there in the summer period where fish collect...we forget or dont think about.

as for me its drop shot season and i cant wait for this period to exploit!

Seasoned angler? LOL Now that's funny.

Im aware of the thermocline, but have never exploited it.
Maybe soon.
Do you drift over these areas or anchor?

Do you ever fish the break without seeing fish there?

 Kelly… I created contour maps up-front on every lake I fish and are stored on my Elite 7 HDI. When creating these maps I first do a perimeter run completely around the lake with polarized glasses paying close attention to fish sightings, old and new beds and structure… I recommend every angler should at least do this before fishing any new lake. I then mark waypoints where these spots are located on my contour map.

When the thermocline forms I basically know where large concentrations of fishes once occurred… I then target that depth where the thermocline break occurs or slightly shallower running the sonar and Down scan imaging along those depths. I basically ignore or rule out drop off breaks and pay closer attention to areas where the contour lines are wider or flat-like. I note where schools of fish are located with waypoints and fish them. If an area looks good on the map and I don’t see fish elevated on the sonar it could mean the fish are hanging close to the bottom in the sonar blind spot or there are no fish. If the spot looks good I’ll trust my instincts and spend time to investigate. Ive picked up some good fish this way.

Drifting with the wind using the trolling motor along a contour is a great way to cover water. It is slow work at significant depths with tiny light jigs sometimes taking 50’ bites out of a contour is more efficient.

Below are some sonar screen dumps of B.Gill goldmines… in this case however they were small in size but does not rule out a significant fish or two in their midst… just recently I tagged a master angler B.Gill by spanking the school until I started tagging better fish.

Wow don't ever see fish like that on my sonar. So your Lowrance Elite 7 has mapping capabilities? None of mine do and I've found the Lakemaster map chips not that accurate in my area.

Yep... i do depend on my unit for great contour maps... find the structure I find fish... and there they are. 

what model are you running Kelly?

Hummingbird 1199 on big boat, HB 571 on my little 4 by 8 boat, still haven't pulled the trigger on a kayak. The 1199 has a Lakemaster chip but can not make my own maps without buying the Auto Chart stuff. The new Helix model has built in map capabilities so have been thinking about getting one for the small boat.

These sonar units are all new to me, have only had them for 4 plus years, never owned or used one before then. Never seen a Lowrance in operation so don't know which is better.
very nice explanation of the thermalcline. i was trying to explain this to a bass fisherman the other day and he was like huh! he said he could catch bass anytime of the year except summer. i told him to fish the thermalcine and he would probably catch fish, AND not only bass.

one thing that i might add is that not all lakes will have a thermalcline. Kentucky lake for example has no thermacline because of the current and wind, it may have a faint signature in some areas but nothing that really matters. a real fertile lake will more than likely will have a hard thermalcline because of the decaying wood and plant matter.

a comment on the sonar units. until recently Lowrance had the patent rights to down imaging for dedicated crystals in their transducers. only the new Mega series from Humminbird has a dedicated down imaging crystals. the helix and other models use a stitched view from the side imaging which makes them less clear than Lowrance and you will miss some returns directly under the boat. Garmin is back to making theirs with a dedicated down imaging crystal like Lowrances since they won the final lawsuit.

if i were to buy a new sonar unit, i would wait until the first of the year until the new models arrive as Humminbird may have some new options as far as down imaging is concerned. right now Lowrances down imaging is superior to the others.

either way you can still find the thermalcline using 2d sonar with the sensitivity turned up as Slip mentioned.

Tracy thanks for that update! So much going on with electronics it just gets better and better! The Mega imaging on the 9” plus models for Humminbird Helix has blown me away…. Crystal clear graphics… just amazing. Onboard contour mapping seals the deal.

Ive had my Lowrance Elite 7 HDI now for over 4 seasons… I feel my performance has exponentially exploded with this unit in my arsenal and think I have bottomed it out and need to move on… side imaging yes… I can only imagine how handy that would come in. I need that onboard mapping as well.

My 1199 has down and side imaging, my small one has neither.
Ken has hit on a crucial piece - knowing the structure.
He spends an impressive amount of his time creating a "build up" of the waters he's fishing.
He has high tech tools, yes, but the goal is to create a layout of the features.
That comes before finding fish. Sure he lucks into fish in the process, but the payoff comes when he can confidently say both WHY and WHERE.
Lots of people get hi-tech fish finders, hoping it will point out fish. What I see Ken doing is learning where the fish must be... And then meeting them there.


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