Fishing the Late Summertime Thermocline

article by Kenny Covington

The dog days of summer are now upon us.  Not only are the daytime temperatures at their highest point of the year, but the water temperatures are also.  A lot of the deep-water fish that were in so much abundance at the beginning of summer, now ghost the anglers using their high-tech electronics in search of their whereabouts.  Which begs the question, “Where did the bass go?” 

This late summer bass movement is due to the thermocline. Once the water temperatures climb to a certain point, when it comes to lakes, the warm layer of water being heated by the sun sits on top of a much cooler and denser layer underneath it, and they are both separated by the thermocline.  The much cooler water holds less oxygen causing the bass to move from their initial summer deep stages. 

When these summer bass move, they do one of two things:  they either suspend just above the thermocline or they move to extremely shallow water.  In both cases the bass movements have more to do with oxygen content in the water than it does the availability of a food source.  The food source will be wherever they decide to set up due to the same reason the bass are moving, better oxygen content. 

So now that we have determined the movements and whereabout of the bass, how do we go about catching them?  First let’s look at the fish that suspend.  By suspending, I am referring to fish that will move into areas and not relate to the available cover.  The bass will suspend over humps, inside of timber lines, deeper grass lines and even in the middle of a creek channel.  These fish almost relate more to the available schools of bait than they do the cover that may be on these structure areas.   

The suspending aspect of the bass behavior is what makes them so difficult to catch.  I am not saying they can’t be caught; I am just pointing out the difficulty in getting them to bite.  Suspended fish are in a neutral mood and usually stay that way unless there is a dramatic barometric change, which might trigger them into feeding. Fish that relate to cover or to structure breaks are generally at some point, active in their feeding habits, making them easier to catch. 

Suspended bass that relate to schools of baitfish can usually be seen on your electronics sitting just below the schools.  As the shad migrate the bass will move along underneath them and feed on the lower side of the school.  This feeding behavior is one of the main reasons they are so hard to catch.  When these bass corral the shad and feed on the surface, they become a bit easier to fish for since you can determine their location. 

The key to catching bass that have shown themselves is two pronged: you must have the right lure and be accurate with your cast.  I believe casting accuracy to be the most important aspect of the two.  You want your lure to land within a few feet of where the fish are hitting the surface.  Those fish are the most active and will not take the time to really inspect what the lure presentation is.  A cast that is a few feet off target gives the fish time to inspect and determine if it is worth chasing or not.  Often these offerings are ignored. 

When it comes to lure selection, I want a lure I can cast a long way and is something that resembles a shad. My personal choices are a Spook, a Rat L Trap, an In-line Mepps spinner, and a small spinnerbait with double willow-leaf blades.  All these lures should be worked extremely fast and once they are out of the strike zone, quickly retrieved to make additional casts. 

The second movement of bass from the thermocline will be to extremely shallow water. I have caught bass in 90+ degree water in depths less than a foot.  I have found these fish to be easier to locate as well as catch in the months of August and September strictly because of their locations. Remember, water temperature isn’t the priority, the abundance of oxygen in these shallow areas, which naturally brings with it an abundance of forage, is. 

Once you start seeing large schools of shad dimple the surface, this is a good sign the better water quality is in the shallower depths.  Bass are opportunistic feeders and by moving shallow, their lives get much easier.  They don’t have to work as hard to survive.  If your lake has shallow grass or flats with grass patches, these areas are bass magnets.  Wind blown areas are always good as the wind will stir up the water, increasing the oxygen levels.  Rip rap or rocky banks with wind blowing on them are also great areas to look for actively feeding bass. 

My lure choices are basic this time of year when fishing shallow water but the one thing I have noticed over the years is that I do better on smaller lures.  My standard lure choices are a Pop-R, a small 1/8th ounce Stanley Spinnerbait, a shad colored 1.0 squarebill crankbait, a ¼ ounce chrome/blue Rat L Trap and a red wobblehead with a six-inch natural colored worm.  These smaller lures are great at catching numbers of bass but will also catch the larger fish as well. 

Fishing the thermocline can be tricky but if you will keep an open mind and have a bit of patience, you might be rewarded with some good late summer fishing trips.  As always this time of year, be careful on the water as more and more people will be out trying to enjoy the end of summer.  The heat can be extreme this time of year so make sure you stay hydrated, use sunscreen and don’t forget to catch one for me!  See you next month!