Fall Turnover?

[TNFL]

I know every lake is different and it is a general question, but when do the lakes turnover? Is there generally a 2 week period or a rule like a week of 40 degree nights or something?

And also, what works post TO? I haven't fished much in the fall, I usually do some catching up with my golf. But I just got a new/used boat and definately want to get some use out of it before winter.

[jalberg]

This topic has puzzled me as well. All I know is that it occurs when the surface water becomes cooler than the deeper water below it. There are also several factors determining how early or late a lake will turn over. Obviosly weather, but also the depth, size, and water clarity. Last year I kept a close eye on my home lake and never was really sure exactly when it turned over.

[TurnUpTheFishing]

I dont believe it happens at a specific temperature. It happens when the wind mixes the cooling surface water with the already cool deep water. One of the signs that a lake has turned is floating debri/decaying matter that was once on the bottom of the lake can be found floating on the surface.

[RK]

Hiya -

Turnover is really varible from lake to lake, and year to year.

This'll be a fairly basic synopsis of the process, and I hope those that know this aren't taking it as an oversimplification, but it's new to lots of folks...

Basically: Turnover happens because lakes stratify. From the beginning of summer on temps from the surface down gradually decline until they reach a level where not enough light penatrates to warm the water at all, and since warm water 'floats' there's never a chance for lower levels of water to heat up. At this level more or less there's a band of water where the temperature decreases rapidly within a few feet of depth - the thermocline. Below that layer the water is basically a uniform temperature. Once the thermocline is established, in many lakes the area below the thermocline goes anoxic, because there's no mixing of surface water to resupply oxygen at all.

Thermocline depth varies from lake to lake. Generally speaking the clearer the lake the deeper the thermocline. A clear lake may have a thermocline in 25 feet, while a dark water lake may haveone in 13 feet. A good depthfinder tuned in will be able to mark the thermocline. The rapid change in water density as the temp drops in the thermocline will read as a fuzzy line on a graph. Some lakes with different basins may have thermoclines at different depths in each basin. Other lakes, either because of wave action (mille lacs) or current (Lake of the Woods) never get a thermocline.

On top of that, thermocline density - or "firmness" for lack of a better term - varies from year to year too. This year with the long stretch of high heat thermoclines set up hard on a lot of lakes. A couple years ago when we had a really cool summer, some lakes never stratified completely at all...

In the fall, this process reverses. Surface temps cool and sink, mixing in the upper layer above the theromocline. When temps drop to a level below the thermocline's temp, the thermocline breaks up, mixing the upper and lower bands of water and re-oxygenating the deeper areas below where the thermocline had been. Some years this process is so gradual it's barely noticable. Other years, sudden drops in temperature when the temps are close to equal, or a drop in temp combined with a big wind can cause turnover to happen literally over night. When a catostrophic turnover happens, you'll see all kinds of gunk and goo in the water, the water can get REALLY murky, and the lake can even smell bad from all the leaves, dead who knows what, loon [PoorWordUsage] and other organic matter that had settled below the thermocline getting stirred up. Fishing usually goes to dump at that point too...

As to when it happens - as I said it varies. My suspicion is it'll be later this year because of the high temps and solid stratification this summer, but a cold snap and an Alberta wind storm at the right time can change that. On years when thermoclines are weak it can happen amazingly early. The cool summer we had recently was a good example. There were lakes that turned over in late August.

Turnover's wierd. The rule of thumb has always been shallow darker lakes go first, then bigger clearer lakes later on. Most often that's accurate. If you pay attention you can lake hop and avoid it altogether.

As to post-turnover tactics... immediate post-turnover, my preferred tactic is to fish somewhere else Once things settle down (usually just a couple days) plastics, jig and pig, slow-rolled spinnerbaits, etc. along deep green weeds has always been my route. By the time turnover gets here I'm usually pestering the muskies more than bass, but when I have bass fished late, that's been my tactic...

Hope that helps a little. Honestly, this is the simple version...turnover's complex as all get out...

Cheers,

Rob Kimm

[Deitz Dittrich]

very good read RK.. thanks!

[TNFL]

So, for those of us that don't get out every other day to see when the lake actually turns.

As long as it doesn't look turned over, you should be fine, since the fishing recovers in a few days. And the fish should be in the same spots shortly after turnover as they were shortly before turnover. ?? (see Fall Presentations)

[Fever]

Not exactly sure, but after turn over there is no more thermocline which means that even the deepest of deep spots will have oxygen, which means that the fish will be a lot more dispersed. Why... Because they can. They should still be relating to structure but in most lakes they can then (after turnover) relate to much more structure, as the bait fish will be doing this... In my experiance the fishing right after turnover even a few days after is much more inconsistant and is actually difficult. I guess this applys a bit more to Walleyes than bass but still, no theromcline does mean more area for bass to follow prey fish schools.