[oldschool]

Have ever wanted to know where the big bass go after the spawn?
During pre spawn and the actual spawning cycle we read about and catch big bass, however following that period the lake seems to swallow up these big bass until next season. Occasionally one is caught, usually at night.
The answer to that question is both simple and complex. Big bass are never far from their preferred prey and depends on the lake classification and of the type of bass you are targeting.
Where I fish in highland deep reservoirs, big bass establish home zones in 15 to 35 feet of water. The reason for this is that is where the thermocline is located and big bass seek the most comfortable water temperature that has good DO levels and offers both security and prey. Where is this location on your lake? Outside water with structure and cover that holds prey and gives the big bass the advantage to easily catch the prey they seek. The big bass hold in there home zones and move up toward the shore line at dusk and roam at night. Largemouth bass will move up to shallow water 2 to 10 foot depth, smallmouth tend stay a little deeper on isolate structure near break lines and spots tend to move up to gravel or rocky breaklines. All big bass like to locate near wood on deep breaks.
Where do you fish during the late spring, summer and fall? if it is not outside, you may not be fishing the right locations.
Only a few lures can work below 15' depth and represent the prey bass are targeting. Swim baits, jigs, slow rolled spinner baits and big plastic worms are the type of lures that catch the majority of big bass during the off season.
Tom

 

[TampaCountryBoy]

Thanks Tom Although I believe I understand thermocline, can you explain that term a bit more. When it occurs, is it just when the lake turns over or does it exist all year long? Clarification would be helpful. Lately I have been hearing conflicting theories regarding the position of Bass to the thermocline. In Florida deep is based on the water you are fishing. Deep could be a little as 10 feet on some of our lakes, but then we have lakes with much deeper water. How about rivers does thermocline exist there as well. Just some clarification would be helpful. Thanks for your time and information

 

[KeithsCatch]

TCB,

I can say that in a river due to the moving water there will not be a thermocline. Even on the St. Johns which has fairly slow water. It is enough to mix up the water sufficiently to keep thermoclines from forming.

Here is a definition courtesy of Wikepedia:

The thermocline (sometimes metalimnion) is a layer within a body of water or air where the temperature changes rapidly with depth.

Because water is not perfectly transparent, almost all sunlight is absorbed in the surface layer, which heats up. Wind and waves circulate the water in the surface layer, distributing heat within it somewhat, and the temperature may be quite uniform for the first few hundred feet. Below this mixed layer, however, the temperature drops very rapidly—perhaps as much as 20 degrees Celsius with an additional 150 m (500 ft) of depth. This area of rapid transition is the thermocline.

Thermoclines can also be observed in relatively shallow lakes. In colder climates, this leads to a phenomenon called turnover. During the summer, warm water, which is less dense, will sit on top of colder, denser water that sinks to the bottom, with a thermocline separating them. Because the warm water is also exposed to the sun during the day, a stable system exists and very little mixing of warm water and cold water occurs. One result of this stability is that as the summer wears on, there is less and less oxygen below the thermocline, as the water below the thermocline never circulates to the surface. As winter approaches, the temperature of the surface water will also drop until it approaches 4 °C (39 °F), which is the temperature at which water is densest. 4 °C is, generally speaking, the temperature of the water below a thermocline. When the entire body of water is at or close to 4 °C, 'fall turnover' begins - the thermocline disappears, (or, to say a different way, it reaches the surface) and the water from the bottom of the lake can mix freely with the water from the top. This process is aided by wind or any other process that agitates the water.

As the temperature continues to drop, in those locations where it does, the water on the surface begins to get cold enough to freeze and the lake begins to ice over. A new thermocline develops where the densest water (4 °C) sinks to the bottom, and the less dense water (water that is approaching the freezing point) rises to the top. Once this new stratification establishes itself, it lasts until the water warms enough for the 'spring turnover,' which occurs after the ice melts and the surface water temperature rises to 4 °C.

 

[oldschool]

Thanks Tom Although I believe I understand thermocline, can you explain that term a bit more. When it occurs, is it just when the lake turns over or does it exist all year long? Clarification would be helpful. Lately I have been hearing conflicting theories regarding the position of Bass to the thermocline. In Florida deep is based on the water you are fishing. Deep could be a little as 10 feet on some of our lakes, but then we have lakes with much deeper water. How about rivers does thermocline exist there as well. Just some clarification would be helpful. Thanks for your time and information

Jim can define this condition better than I can, however let me give it a try. Thermocline as I understand and apply the terminology is the first water column temperature break below the surface water temperature. Temperature break is usually measured in about a 3 to 5 degree change within a few feet. Summer stratification creates a dense temperature break of warm surface water to cold deeper water that is easily located because of the abrupt change. Thermoclines exist whenever there is a water column temperature break. The reverse is usually the situation in winter where the colder surface water meets deeper warmer water. In most thremocline temperature breaks the dissolved oxygen level are ideal for bait fish and bass. The dense thermocline can hold dissolved oxygen from mixing down into deeper layers colder layers during the warm water periods, unless wind or current mixes the layers. In Florida you have a lot of lowland reservoirs and natural lakes and rivers, all spring feed. Altough the lakes are shallow compared to other reservoir types, a thermocline can still exist. Springs located in deeper water may be your best choice because they provide the same condition for prey and bait fish as the thermocline does for the deeper reservoirs.
Good sonar can pick up the water density change and the life zone associated to the thermocline is also easy to meter with sonar. Thermocline looks like a dark line in the water column on sonar and bait fish look like clouds of suspended fish. If you see the bait fish at 10 feet all over the lake, you should be able to tune the sonar to define the thermocline dense water break line. Power generation lakes create current and mix things up when the current is running, similar to a river. However in any body of water the life zone is there and the big bass tend to locate very close to the lower levels of that depth.
Tom

 

[TampaCountryBoy]

Thanks to both of you, This is going to take some time to absorb, I appreaite the info but for some reason the ole brain ain't absorbing the info. ld: Thanks again

 

[oldschool]

Thanks to both of you, This is going to take some time to absorb, I appreciate the info but for some reason the ole brain ain't absorbing the info. ld: Thanks again

If you had a thermometer with a weight and lowered it down into the water, the surface temperature during the winter would be cold, lets say 50 degrees. As you lower the thermometer and could read the temperature while it was going down the temperature would start to rise if the water was warmer deeper. If the temperature climbed from 50 to 53 within a foot or so, say between 11 and 12 feet, that would be the thermocline. If the temperature fell from 50 to 47 degrees, that would also be a thermocline. Whatever depth the reading changes quickly is where the thermocline is located. We don't use thermometers anymore with weights to lower into the water, so we use our electronics to see where the warmer water meets the colder wate. The colder water is heavier, more dense, so the sonar signal shows this transition as a dark line. The bait fish and bass tend to locate at the temperature break and the sonar picks up the fish locations and I call that depth the life zone. The life zone and thermocline are usually the same depth. Clear as mud?
Tom

 

[hi steel basser]

I have a few questions on this subject, mainly about turnover. How do you know when it's happening, and how do you fish it? Also, how do you set your depthfinder to locate the thermocline? I will think of more ?'s later.

 

[TampaCountryBoy]

much better,

so can I safely assume the baitfish and Bass would be located in the warmest water with the highest Oxygen level. This could be above or below the thermocline line we see on the sonar? Does the thermocline really play that important part in fishing if we ID the baitfish location and fish to those levels and structure. Can the thermocline be considered a structure as patterned as such. Sorry I am being so simple-minded about this.

 

[oldschool]

Before digital sonar became sensitive enough to reflect the deference's in water density, the only unit that could was Lowrance's X15 paper graph and few anglers knew how to adjust it properly. Before that we had to dip electronic thermometers to locate thermoclines. The realization that the life zone and thermocline are associated took several years to put together. You can't always locate bass and baitfish, however you can locate the thermocline without finding bait fish. This is why I always meter the marina to try and determine where the thermocline and life zone is that day. This is the depth I start to look for bass on structure and the location is dependant on the seasonal period. The thermocline is one of the most important factors to determine, because big bass on structure where the life zone and thermocline come together. Locate the prey on structure that holds bass in deep water and that is where the big girls stay after the spawn.
Tom

 

[KeithsCatch]

TCB,

Most of our lakes here in Florida except some of the deeper ones in Central Florida do not get Thermoclines. Our weather is not drastic enough to create them here. So for us thermoclines rarely play a factor in fishing here in Florida.

Now if we had winters that stayed in the 40's for a long enough time to drop the water down into the 40's and then as it began to warm in the fall it would create a thermocline. Typically the fall is when thermoclines become apparent in lakes. You will know too when a lake has turned over. It will stink and you will see clumps of bottom material floating on the top with lots of air bubbles. This means the water temps is the same at all depths and the fish are spread out at all depths. Some are on the bottom some are mid level and some on top. This is why it is tough fishing during these conditions.

But fishing lakes that are less then 10 feet deep like what we have plus having mild winters means we don't see thermoclines here. But some lakes that are in the 20-30 feet depth and like what happens on Kingsley lake in Keystone Heights thermoclines can develop. But like I said we just don't get extremem weather one way or the other really to create major thermoclines. Heck in some lakes there are 2 thermoclines going on at the same time. This can be seen by increasing the sensitivity on your graph and a solid black line will appear on the sonar. When you see this it is a thermocline.

 

[oldschool]

It's not the Florida climate, it's the geography. Southern California's climate at sea level is similar in temperature to Florida's, however Florida is flat and California is mountainous. Flatland reservoirs may stratify into thermal layers and the big bass still seek the deepest water available to use as a shelter close to their preferred prey. What is different is the abundant cover available and the lack of deep water structure.The big bass spread out more and become independent and territorial. I posted Bass are Bass and thinking about doing something more on Florida LMB bass verses northern LMB bass. Florida LMB are a different bass and require specific presentations.
Tom

 

[TampaCountryBoy]

Great information and I believe it is starting to sink in, thanks for the education. Keep it comming. Tom I can't wait to read your input on Florida LMB

 

[oldschool]

Great information and I believe it is starting to sink in, thanks for the education. Keep it comming. Tom I can't wait to read your input on Florida LMB

I did post Folrida LMB a different breed. It regressed to world record bass a little.
Tom

 

[Jared]

I love your posts Tom! I feel like everyone of them takes me to school. :thumbup01:

 

[Ouachita]

In warm months when I find the thermocline depth I've eliminated all water below it, narrowing my search to a tiny fraction of the total lake. If it happens to be at 21 feet below surface, I pay attention to any water at or above that mark. That includes from thermocline depth to mainlake shore, humps in mid lake that at at least poking shallower than 21 feet, or any cover or structure poking up into the top 21 feet of water. A bridge piling might stand in 40' of water, but the top 21' of it will be the life zone.

That isn't to say no big mama bass won't go deeper. She will to escape danger, but can't survive down there long enough to consider fishing there. Some species of fish can last longer deeper, so seeing some on the sonar at 30 feet doesn't alert me to think 'bass'.

The contact zone between upper warmer and deeper colder/denser water, the thermocline, can be many feet wide. The thermocline in my instance might start at 21' and show on the graph to extend to 30'. Thick zones like that can hold DO deeper. The main limitation is there is practically no DO, not enough for bass health, in the lower cold water outside the mixing zone. There is likely some DO, just not enough unless there's a 'forest' of vegetation in that cold water. Plants oxygenate water above them, so in that case the thermocline mostly suggests a comfort zone depth rather than a matter of life and death concerning O2.

In those south Florida spring fed lakes there most likely is a thermocline. Maybe it doesn't show up since it occupies practically the whole depth. The immediate area around a spring can be a little deeper, the incoming spring water cold and flowing under the warmer surface water. Maybe the cold water (hyperlimnion) is only 6" thick compared to 9 feet of upper warmer water (hypolimnion) with a mixing zone (metalimnion) of only 1 foot. In order to view a sonar horizontal dark banded thermocline the high sensitivity setting needed often produces other viewing problems like false bottoms and erratic depths.

Next time out during post-spawn try to stop beating the shoreline for "used" bass and try fishing those outer waters for a change, down to about thermocline depth. Right now, during the spawn, bass are bottom-oriented eating crawfish, so stick to shallow. In post-spawn they will be shad-oriented off the bottom, so fish out there wherever the shad are. If you find shad there's enough DO for bass too. Crappie spawn very close to bass timing and places, so find some crappie/bluegill beds where bass feed on the fry and later fingerlings. It's revenge time for the bass.

Jim

 

[KeithsCatch]

Good info as usual Jim. Is Tom on vacation? I haven't seen him around here much lately.

 

[oldschool]

Post spawn bass in general are tried and beat up after the spawn. You may see the big females just cruising along below the surface outside the spawning areas before they recoperate and locate on some outside structure. It has been may experience to leave these bass alone because they are not interested in eating, they are trying to survive.
Once the bass establish a location, then target them. How to tell a post spawn cruiser form a pre-spawn?, the post spawn bass move slowly and usually have a very dark color, the pre-spawners are move with determination and usually are a vibrant watermelon green color.
Tom

 

[Sirius Rich]

Post spawn fishing is becoming my favorite. I think I have it dialed in, at least in the Southern lakes. I look for the drains coming out the spawning flats heading to the bass' summer holes. These are the hiways the bass use and as they recover from the spawn they get hungry. This is a good time of year to throw topwaters. Spooks, Frogs, Sammys, Ricos etc...It is also hard to beat a jerk bait too. As noted above the fish are in bad shape and it is important to handle them carefully before returning them back to the lake.

 

[oldschool]

Check out "transisitons".
Tom

 

[JEVPhoenixBass]

Before digital sonar became sensitive enough to reflect the deference's in water density, the only unit that could was Lowrance's X15 paper graph and few anglers knew how to adjust it properly. Before that we had to dip electronic thermometers to locate thermoclines. The realization that the life zone and thermocline are associated took several years to put together. You can't always locate bass and baitfish, however you can locate the thermocline without finding bait fish. This is why I always meter the marina to try and determine where the thermocline and life zone is that day. This is the depth I start to look for bass on structure and the location is dependant on the seasonal period. The thermocline is one of the most important factors to determine, because big bass on structure where the life zone and thermocline come together. Locate the prey on structure that holds bass in deep water and that is where the big girls stay after the spawn.
Tom

Eagle's version was/is the Mach One. I ran one for many years and still have an old unit. Also remember that water density i.e. colder water, will also determine to some extent the amount of dissolved oxygen that is available for the fish. Oxygen levels can be a bigger barrier to fish depth than temperature. If you watch your graph closely you will see fish at and below the thermocline and others moving back and forth. The thermocline is an "edge" just as any piece of structure is that you might see.

Go fishing!