Summer Lakers ... Semi-Report / Thermocline??

[Bis4ben]

So packed up and went into Algonquin park this past weekend in search of some lakers. Started by trolling gang trolls paired with little cleo's or worm harnesses around the lake in what i figure was roughly 30-35 ft ( 8 colours of the lead core). We picked up our first fish after just over an hour of trolling. We pulled the U-turn and went back to the spot we figure the hit would have originated; this was roughly 80 FOW about 50ft from shore (steep drop off). We started jigging 3/8 oz heads with 4" white grubs and were unsuccessful for the next 30-45 minutes. Pulled up our lines and started moving down the lake searching for greener pastures. The water was gradually getting shallower for the next little bit and after about 20 minutes we came to a spot that rose up from 50 to about 28 FOW. The 28 foot depth was a rather constant flat that ran in between two points. We started jigging away while slowly drifting from 60-30 FOW and found the lakers pretty quickly in this spot which got both myself and brother psyched. Most of the fish came while jigging right off of bottom from 40-45 FOW while hugging tightly to the 25 ft shallow flat. We boated a good few, below is my biggest of the day as well as my brothers first on the day.

What i am curious about is if anyone has a rule of thumb they could share with regards to determining the thermocline depth. I know this layer will vary from lake to lake but there must be a quick way to roughly figure where this layer should be in the column based on surface temp, surface area, spring fed etc ..?? What factors do you consider when determining depth for lake trout fishing??
I've done a little research online but 1/2 of the info seems to contradict the other half. Any suggestions or a helpful article or blog on the topic would be great. Secondly, do most ppl try to fish just above this line? Just below this line? Maybe Jig all the way through the thermocline? I recall another FH member mentioning jigging in 90+ FOW ... this would definitely be below the thermocline, right? Or am i just overthinking the entire thing?

Anyhow ... thanks for reading.

My Biggest on the day


Bro's first of the day

[tbone1088]

easiest way to find it is turn the sensitivity up on ur fishfinder, it will show up as a band across acertain depth.

[tbone1088]

just seen your second question Most fish species stay at or above the thermocline because of the lack of oxygen below the thermocline. However, in cold lakes there is usually enough oxygen dispersed through the layers of the lake so the thermocline is not an issue. Basically if your fishing for trout don't even worry about the thermocline

[Out4trout]

Nice report, some fine looking lakers!!

Thermocline...
Very much lake specific. On warmer lakes, once the lake stratifies, trout will only venture briefly into the thermocline. On spring fed cool lakes, esp smaller lakes, there likely won't be much of a thermocline to consider.

For southern Ontario deeper lakes, typical thermocline starts at 25ft and reaches 35ft. Below the thermocline there will only be cold water species such as lake trout, whitefish, herring and some baitfish. The occasional pike as well. Above the thermocline, all the warm water species such as bass and panfish.

As for fishing, I will generally fish below the thermocline for lake trout. But... often just below, depending on what the sonar is showing. They will often suspend 80 ft or deeper, and venture up to 40ft to feed. Finding where the bottom of the thermocline intersects a shoal, and you are in prime territory.

Finding the thermocline, a few ways, as mentioned graph will show the line, or old school with a thermometer on a drop weight.

[Bis4ben]

Thanks Tbone. I had no idea that seeing the difference on the depth finder was possible. I suppose that makes sense, two masses of different density; i'll see if my portable finder is sensitive enough for this.

Out4trout ... as always very informative. I appreciate the response.
I may rig up a thermometer on a weight ... truthfully it just sounds badass!

[flewdoggII]

I have tried the thermometer on a weight trick. It works okay. You can buy a thing from Vexilar called the Deptherm, it measures temperature and tells you how deep the measurement came from. It's about $10 plus shipping (couldn't find it on local store shelves).

Here's a link to a place that sells the Deptherm: http://www.fish307.com/vexilar-deptherm/

[Walleye'm Fishing]

Beauty lakers!