Lake Turnover & Its Affects on Fishing

[Swede]

Thought this may be a good topic of discussion. 

Each fall as the water cools in the upper stretches of the water column, it reaches a temperature where it becomes more dense than the water layer below and falls to the bottom pushing warmer less oxygenated water to the surface.  Here's a more detailed explanation:

http://www.islandnet.com/~see/weather/elements/turnlakes.htm

How does turnover affect bass fishing and how do we catch bass under these circumstances?

[-Shawn-]

It pushes the fish Shallow, where the turnover has much less effect.  In my opinion, this is the real reason for the fall migration of fish and bait to the backs of creeks and Pockets. 

[coldfront]

one of the key issues I didn't see was discussion about how nutrients (from dead/decaying product) sinks below the thermocline and then is 'trapped' as those lower layers don't circulate until turn over...

those nutrients (nitrogen, sulfur, etc) get re-distributed and then get 'used' by algae...causing a typical 'bloom' late in the season...and the water gets murky/stained...

around my 'neck of the woods' the water takes on a brown cast...as the prevalent organism that 'blooms' is actually a type of diatom...


fish disperse widely...or can...usually this time of year, best approaches are to target shallow water fish that are cover oriented...stumps, rocks/riprap...or shrinking weedbeds on flats...even so, fishing can be a bit hit/miss...

I've heard those shallow fish tend to be 'resident fish' that were typically there all summer...keep in mind that the waters I fish also DON'T have shad populations (gizzard up here) but are bluegill/crappie forage based...so we don't get those massive fall shad migrations that the 'classic' waters get...

[Swede]

Seems like there would be many turnovers, not just one with the gradual cooling of the water.  Makes sense going shallow, as does reasoning for fall push of bait fish to the creeks.

[Mike Cork]

First there is NO ABSOLUTE in bass fishing. I can counter every statement made about fishing 

Take this one about turn over and I'll pick on you Shawn cause I know you and will just buy the next bottle of crown

A typical lakes thermocline will run about 20-30 depending on the body of water and what part of the country it's located. During the summer months you will find fish just above this thermocline as that is the most comfortable water for the bait which are very sensitive to water temperature, food, and oxygen. During the early and late parts of the day throughout the summer balls of shad will move to the surface but rarely will you find them there all day without something chasing them there (again there are no absolutes here as I have a lake just down the road that the shad stay on the surface all day long  ) Shad move around above the thermocline in all depths. IMO there are two different types of bass, your open water fish and your cover fish. Cover fish will stay shallow and live in brush and grass all year long and wait for food to come to them. Open water bass will prowl all day looking for that banquet. For both types it's feast or famine. Bait moves in or they find it but then it's gone. What all this means to me....

During a fall turn over resident shallow water bass (bass that have been there all year) become more active for two reasons, neither to do with the turn over. 1rst during the fall, water temps fall and become more comfortable for bass, so they become more aggressive. In the heat of the summer a bass's strike zone becomes very small as they can't afford to spend excessive amounts of energy to chase food that they may not catch. With their metabolisms so high missing prey could end up being a deadly mistake over time. Cooler water brings their metabolisms into check and they can afford a larger strike zone to include cruising shallow flats early and late making reaction baits like spinnerbaits and buzzbaits very effective. Now realize that the entire food chain is in the same comfort zone so the brim and perch are also moving and more vulnerable. 2nd is typically in the fall most lake managers have their waters levels low preparing for the winter rains. This reduces the shoreline cover that the shallow water resident fish have which makes them more vulnerable to us a fisherman. So did bass move shallow because of the turn over or where they there the whole time and we just figured out we could catch them?

Open water fish? Well this is a tough one as they will cruise points, drop offs, ridges, humps and any other structure as road maps in their daily hunt for food. Wind plays a huge roll in where you will find them. In relation to the fall turn over: If the cooler more comfortable water on the surface falls to the bottom wouldn't it make sense that this would create a deep water comfort zone for bass and bait fish? So why would either move to the surface or shallow water?

I believe that the fall migration of bait fish and then bass has more to do with warmer waters well past the fall turn over. Once the water cools enough to turn over, the lake as a whole become very comfortable for fish and you can catch them just about any way you want to if the weather conditions are right. I believe the migration to the backs of major creeks doesn't happen until the main lake becomes too cool for shad and they start dying, then the shad migrate to shallow water that will warm quickly with the sun in search of a comfort zone.

I truly believe that the sun is a major factor in this migration, it's what creates the food source for the shad and the shad are the food source for bass. Moving to shallow waters where the sun can warm the water and create food or to the backs of creeks with in flow of water that will be warmer (because most creeks are just a trickle this time of year and the sun has been working on them) and full of nutrients is just survival for the shad and the open water fish will follow them, add to that the resident fish and BAM you have a fantastic day on the water.

Now to be honest I can personally counter most of what I have said here but this is what I have come to believe.

What's everyone elses thoughts.

[-Shawn-]

Mike, I will debate almost all of those points, but not while I am posting on this dang phone! lol

The reason I think the turnover has alot to do with fish migration is that I can watch Bass leave deeper structure on the electronics about 2 weeks prior to turnover and leave the shad behind. The main reason I think they do this is the low oxygen saturation during the first week after turnover. The bigger fish move to grass then to alge covered wood when th grass gets in bad shape. Some main lake fish wil stay in the main lake, but suspend just below the surface where the oxygen concentration is higher due to wave action.

I hate typing on this phone! Lol

PS I will be waiting on my bottle of crown! Lol

[coldfront]

shawn...

I like that your observations indicate the bass leave deep structure...

but thinking they leave 'two weeks before the turn over'  which results in an 0xygen 'sag' one week after turnover...doesn't make sense...

what did I miss?

Here our waters typically 'turn over' when surface temps get back to 60°F (off summer  highs in the mid-80s)...
just thinking...in our case, if our deep structure bass follow suit on your experience...they'd begin moving at about 65°F or so...

wondering if perhaps those fish move up to deepest 'remaining' weedlines and 'follow them' as they recede...and the bait/baitfish that's been 'hidden' in those weeds all summer starts to be available for food?

[Mike Cork]

Shawn your close  In fact your migration theory is sound but take the bass moving to vegetation and then algae covered wood? That's not really because of the turn over is it? Isn't that because that's where the shad are feeding hence resident bass see a banquet.... Bass will live in vegetation as long as it is producing O2, the algae isn't going to produce enough to sustain them so they are not going to move to the wood for any other reason than that's where the shad are feeding...


Just a thought... algae blooms are notorious for fish kills in smaller bodies of water 

[coldfront]

Just a thought... algae blooms are notorious for fish kills in smaller bodies of water 

I know golden algae blooms produce toxins that are part of the problem...

'normal' algae blooms aren't a problem until they die...they through decomposition...they suck out the oxygen...

one of the reasons why those 'no wind, overcast days' in august can be such a problem on some waters...  no wind aeration, no photosynthesis...and higher metabolic rates for the fish...and toss in an oxygen sag...

not good

[-Shawn-]

Cold front, I think they leave because they know the turnover is approaching. The oxygen sag happens almost immediately at turnover and the fish learn that is a place they do not want to be. It is like clockwork in my area. You can have structure fish and bait one day and nothing but bait the next. That is when I follow them along channels just like I do in the spring.

Mike, the grass to wood thing is partly both, bait and turnover. Just prior to turnover the grass is still healthy, by the time a lake really clears after turnover most of the grass has became unhealthy due to poor light penetration and that is when the fish move to wood.  Usually it is algae covered wood because it attracts the baitfish.  This whole scenario usually plays out over a month. For us it usually starts in early September and the lake clears up in mid October.  The lakes will turn again when the water temp gets to the mid 50's and right after it settles the shad and bass head to their winter area's .

This is just my hypothesis that came from my observations, but it is also a pattern that has won me some money through the years.

It is one of those which came first, the chicken or the egg questions.

[coldfront]

shawn,
the question I'd pose is this:

at/right after turn-over...fish seem harder to find...whether they're there and not biting...or not there...

the question is...during this time...have you ever encountered a 'good' bite?  defined by what appears to be a large/larger group on small spots?  around deeper areas?  or are they filtering into/onto flats for feeding?

[Mike Cork]

The oxygen sag happens almost immediately at turnover and the fish learn that is a place they do not want to be. 

This oxygen sag you speak of? Where is it exactly? If the surface water is falling to the bottom and the bottom rising because of it, wouldn't all the water have plenty of O2? I mean the surface water is where all the O2 is and if it falls to the bottom and mixes then the whole lake should have plenty? Or if your saying that the whole lake is going to be weak in O2 where are the fishing going to sanctuary?

I still stick to my belief that the open water fish are still there but chasing the bait fish instead of relating to structure, they roam a lot chasing the food and get pulled off their home points, drop offs, ridges. As they get to chasing food they stick with the food and move around the lake in which ever direction the food takes them. Since the overall water temp is more comfortable they can afford to spend lots of energy keeping up with them and not worry about a safe resting place. Another thing that contributes to this theory is that they are feeding up for winters... Eat Eat Eat

The shallow water resident fish are there because they always have been but are just easier to catch as their strike zones got bigger with more comfortable temps.

Now your super bass will use both IMO, they will not be pulled from the structure but migrate it daily to and from shallow waters. I think the fall the theory of a point or road bed being a hi way is extremely true. Large bass will move from deep to shallow in search of food and then back to deep for sanctuary. However we know that it's going to take a lot of work to pick off 5 biggun's in a given day.

[Camden]

Here is a quote from Gene Gilliland, Central Region supervisor for the Oklahoma Department of Wildlife Conservation


"Large reservoirs or natural lakes that have constant wind or a frequent current will not typically turn over. If they do, it won't be as dramatic as on a still impoundment," Gilliland says.

The wind and current keep the water mixed all summer long and into the fall, so there is not much difference when the upper and lower layers of water mix. The lake won't be stratified enough to have a significant turnover, meaning there won't be much if any difference in the bass' location.

I do believe there is some truth to this. one lake i fish is very secluded with tree lines and high banks everywhere. this lake turned over very quickly. but another one that always has wind on it seemd to have never turned over yet.
now i will say the lake that has turned over i believe is easier to fish because right after a turnover the o2 levels are good at alot of different depths so the fish can cruise around more chasing bait and are more active.

just my thought

[-Shawn-]

Coldfront, immediately before and after turnover, I have done well not paying attention to bait at all. This is one time you will find me right on the bank. Never deeper than the inside grassline.  I also look for arms of the lake that are the least affected by turnover. Ie not deep enough to stratify. 

[-Shawn-]

Mike the biggest part of the lake will be low on oxygen, because the water under the thermocline is normally alot bigger volume wise than the oxygenated water above the thermocline. Take Ivie this year, the t-cline was at 24 ft,but that left alot of the lake with 30-90ft of unoxygenated water below it.

I am not arguing the actual fall feed. I have just noticed that the bass going shallow isn't always because they are chasing bait. 
They just stay there because they are chasing bait. 

[bass1cpr]

   There's only two turn overs a year and they are complete when the water reahces 39 degrees.top to bottom. Water will be at it's most dense point then and the oxygen is distributed throughout the watere colum which allows the fish the freedom to roam which is why they are so hard to find and pattern during this period.
   You may see water stirring from differant break levels which may lead you to think that there is more than one turnover in a season but there's not. Your interpertations are miss constrewed but still affective for your fishing. Does that make sense without being offensive?

[-Shawn-]

Our water very, very seldom even drops into the lower 40's. we have two distinct turnovers, the first is usually when the water reaches 74-75  the second is mid 50's.  The first Is the only one that has a drastic effect on fishing usually lasting about a week and then clearing. 

[coldfront]

Our water very, very seldom even drops into the lower 40's. we have two distinct turnovers, the first is usually when the water reaches 74-75  the second is mid 50's.  The first Is the only one that has a drastic effect on fishing usually lasting about a week and then clearing.

Shawn, what are the characteristics you see at each turnover?  I'm assuming there are algae blooms associated with each?

and how deep are the lakes you are fishing where you see this?

[-Shawn-]

The algae bloom, heavy sediment getting stirred up and the god awful smell of rotting everything.

Second one is the same but on a much smaller scale.

The first is just nasty.

I wish I wasn't posting on the phone, I would be able to explain all this much better.