Fall Turnover in the BWCA

[ZootAlures]

It will be here before you know it. Just what is fall turnover ? I've often heard that phrase and people just throw their hands in the air thinking the fishing will be less productive than other times of the year. How do you determine when the lake system has turned over ? OK say the lake has turned over... Now what ? How will the fish relate in difference to the spring/summer patterns ?

Dave

[pastfan]

This is the best explanation I could find- hope it helps.

The first thing you need to know is that water is it's most dense at 39 degrees F. Water warmer than 39 and cooler than 39 is less dense.

Let's start the cycle in mid summer. In summer, the water at the top of the lake is likely in the 70's, and the water at the bottom of the lake is likely in the low 50's, because that's what the ground / groundwater temp is in northern Wisconsin/Minnesota. There is likely a 'thermocline' in the lake, which means a sharp break where the top sun warmed water and cold bottom water meet. Wind and wave action only mix the warm top layer, and the bottom cold layer is essentially lifeless, as the oxygen gets depleted and isn't renewed by wave action or weed growth. The reason the colder water is at the bottom is that it's far more dense than the warmer water above so it stays on the bottom.

In fall, as the top layer cools, it will cool to a point where it approaches and goes lower than the temperature of that bottom layer. When that happens, the colder more dense water will sink, therefore the top layer will cool and sink or mix with that previously lifeless cold bottom layer. That's called 'fall turnover' and occurs sometime in late September to very early October when the surface water cools to a point in the low to mid 50's. Obviously smaller shallower lakes will cool faster than large deep lakes, so all don't 'turn over' at the same time. Following this 'turnover', the water temp in the entire water column is the same from top to bottom. Fish that couldn't venture into the deeper oxygen depleted water in the summer can (and do) now use the entire water column and will be scattered throughout your body of water as the oxygen level is pretty much the same everywhere.

As fall progresses, the water will cool to 39 degrees and beyond. When this happens, the 39 degree water will remain on the bottom (remember 39 degrees is the most dense) and the cooler water will remain up at the surface, forming ice when it cools to 32 degrees. Therefore in winter you will also have a temperature differential, but it isn't as great as summer. Summer differential from top to bottom may be up to 30 degrees F difference. In winter that difference is 7 degrees from top to bottom of the water column.

Come spring, the ice melts and the sun warms the water to 39 degrees (usually that occurs the day of or day after ice off) and the entire water column once again mixes and is the same temperature throughout. That's called 'spring turnover'. Obviouisly with a much smaller temperature differential it isn't as noticable as fall turnover, nor does it have as much affect on the fish. Following spring turnover, the sun will continue to warm the surface water and the colder water (39 degrees) will remain on the bottom, where it slowly warms to the low 50's over the course of the summer based mainly on ground / groundwater temp. A thermocline (sharp break) will form as the surface warms into the 70's or beyond and the bottom water stays in the 40's to low 50's. Then we start the cycle all over again.

[Casaloma]

Ahh, that lovely time on our lakes between 'post spawn ' and 'fall turnover'. After a brief swim at the beach I got out today on Island, working into the waves we were able to slow the boat to Lindy speed & got bit. 2 eyes 18" & 20" along with the Island 10" to 12"er's.

I gotta keep gettin' better on that lake, she's huge potential.

Later- CLoma

[ZootAlures]

So I should be able to lower a temperature guage in the water and have the same readings at various depths. If there is still a difference between the upper few feet and say 50% down further then the lake has not turned over yet.

Has anyone had any luck with methods like this ?

This seems important so one will know when to adjust the depths of trolling and live bait fishing.

I'll be testing this technique the Full Moon week in Sept and let you know what was determined on he lakes that were fished.

My thoughts were if the lake has turned over I would try and troll deeper water with a three way swivel and bottom bouncer. Fishing Live bait and lures with speed/depth changes.

Dave

[Surface Tension]

Fishing after fall turnover can be a tricky. Here are some things to look for. Put a combination of them together and your back in the game.

Weeds, some of the weeds will have died off come Fall. Whats left will have shiners in them and eyes looking for cover and food.

Warm water, even though there was a turnover the Fall sun still warms the surface water. Getting on the wind blown shores in late afternoon to get on the warm water is a must.

Fall nights cools the surface temps, that shallow shoreline weed bed needs deeper water next to it for eyes to drop into. If theres weeds on the first break all the better and theres where you should start looking during the day. Fall is minnow time again. I prefer tipping a jig with a minnow, working pockets in the weeds. A slip bobber will work but your not covering the water like you would a jig.

[ZootAlures]

Last fall we did well for Northern with the weed pattern. Tall weeds that were visable next to deep water was the key. If weeds were in back shallow bays not a fish around for miles. Now place the tall standing weeds next to deep water and some good action could be found. The fish could be found right next to the weeds or one the other side of the boat casting out toward deeper water. The deeper water produced much bigger fish. We were casting surface lures and the Northern were hitting them hard. Using wire leaders worked well and the fish did not seemed to be turned off by them. The fish were biting so hard the leaders would be bent at right angles and needed to be replaced. The wind pattern was not added to the location of the deep weeds. I'll keep that in mind this fall. No eyes on top water baits though. Will try the jigs/slip bobbers and hang around an area for a while. Normally we run the electric moter catch a few fish and move on. Hours later you can come back with the same results.

Dave

[Surface Tension]

Right, don't bother with the shallow bays, stay connected to the main body of water. Weeds/deep water and minnows jumping is an indication somethings up. Top water stuff is fine for pike and bass but you won't get many eyes committing to them. Eyes will be on the feed heavily but not real aggressive. Slower presentations and a very lite touch for sure.

That sort of contradicts trolling cranks at night doesn't it, which does work. Thats two totally different scenarios that can happen on the same lake. I'd reserve that for gravel or sandy windblown shores, thats if the day temps warmed the water. Personally if you can find the weed pattern or finesse, I think it'll out fish pulling cranks most of the time.

[ZootAlures]

Here is one of the Northern caught last fall. This was found in the weeds next to deep water in Farm Lake. Surface lures got his attention. Another catch and release. Dave