So Many Suspended Lake Trout!, Why? Today I found the answer...

So, every year, I've noticed that as we get to the end of August, the lake trout are suspended everywhere! You can't go anywhere and not see like 4-5 fish on your depth sounder from 10 to 50 feet above the ground. Sometimes it's like 15-20 fish.

But from June to 2nd week in August, you'll never see these fish (unless you're in Whitefish alley, and those fish are suspended whitefish then and not lake trout.) All the lake trout from June to 2nd week in August are hugging the ground so hard that it looks like there are no fish... but they are there... we all know that because they rocket off the bottom for your lure when jigging, almost like they just "appear" out of nowhere.

So what's the problem with suspended fish? In my experience, suspended fish typically don't chase your lure. It takes an act of congress to have a suspended fish get interested in your jig. The fish that typically chase your lure are:

1. Fish on the bottom that you can't see originally on your depth sounder before they separate from the bottom to come to check out your lure/jig.
2. Fish already at the 30 to 50 ft area actively hunting bait fish. Yes, you can rocket past these guys, and they will chase your jig. This is how I typically get my lake trout in late August and September.

So why do all the lake trout suspend suddenly in late August/Sept? Today, I found the answer:

https://www.outdoorcanada.ca/time-to-stop-trolling/

Bonus section:

It always reminds me that Simcoe is polluted with Lake trout. Hundreds of thousands, or even more. Let's try to do the math...

Using right triangle calculation, If (a=100) is the depth, and (β=?) is the length of scan in one direction, and the angle between (a) and ( is ∠a=90 degrees, and the angle between (a) and (c=?) is ∠β=60 degrees, then:

Given a=100 and ∠β=60°,
b = 173.20508

So the length of scan using a 60 degree medium cone angle is 173.2 feet.

Now let's find the area of a circle using 173.2 feet as the radius.

A=(pi)r^2
=(pi)173.2^2
=94242.2504


94242 square feet you are scanning.

94242.2504 to square miles is 0.00338047557966 square miles according to Google.

In the bay, I'm thinking there is about 6 mile long, but 1.5 mile wide area that Lake trout could be in. So that's 6*1.5 = 9 square miles of lake trout just in the bay.

Outside of the bay I'm estimating there is about a 15x10 mile area that lake trout could be in at any time. This is being conservative from my experience of seeing suspended fish almost everywhere right now. 15x10 = 150 square miles.

150 + 9 = 159 square miles of possible lake trout being suspended right now.

Now let's take that scan area from your fish finder of 0.0033804.. square miles and divide it into the total number of possible square miles where lake trout could be.

159 / 0.00338047557966 = 47034.802266 possible "scan areas" that contain at least 10 lake trout suspended.

47034 * 10 fish = 470348 lake trout in Simcoe.

Thoughts? Someone check my bad napkin math for mistakes lol

First of all, fishfinder never tells you the TRUTH - assume you have a half circle scan area from surface to the bottom, with the diameter equal to the depth here.
In reality - it is 3D semi sphere under your boat, right? Expanding sensitivity of fishfinder you are expanding the size of that reliably detecting zone, its not limited to 20 degrees angle, it is extending boundaries well beyond that, almost to the shape of slightly deformed under weight inflated balloon, just think about that, right.
Any fish from any direction comes into this ballooned sphere will be interpreted by fishfinder as coming from bottom, it is using 2D model to render sound images, direct line from transducer to the fish reflection.
So, the "laker from the bottom" is Laker from almost anywhere, possibly the same suspended at half depth, which saw your falling lure from distance.
BTW, I gave up on lakers this year, the water on Simcoe is blooming, very pure visibility and suspended in this algae mess lakers cannot properly see the lure falling beside at the distance.

By the way, it is a very good training for your eyes and fishfinder settings to distinguish between fish approaching your lure from REAL bottom and from the side.

Thank you for your reply.

I understand how sonars measure the distance from the sound rebound to the transmitter/receiver and the habits of lake trout and their hunting style. The only thing I didn't know is why they suspend late August.

If it's fast-moving and coming from the side, I agree that sometimes it's difficult and even impossible to know the difference in some situations.

From everything I know about my sonar, the cone angle is set and does not change. At least on my sonar, medium freq is 60 degrees cone angle, and high freq is 20 degrees cone angle. What does change is the data that is displayed on the display unit. The data recorded is parsed/truncated depending on how you set your sensitivity. I can tell you that for certain because I can record data with all the sensitivity settings to the lowest. Then I can replay that recording and change the sensitivity to find what I missed. If the cone angle changed, then that data wouldn't be recorded at low sensitivity, do you agree? Maybe other sonars are different.

I think your 60 degree cone angle is the included angle (total, both directions)….so in your trig calculations you would actually use 30 degrees. Other than that, I think you could likely find studies that MNR would already have an estimate for trout populations based on net set results at different depths for different durations etc.

Thanks, Drew. I think you may be right, because I found this calculation as well:

So, applying this formula, it would be:

Radius of beam circle, which we'll call RBC = 2 * 100 * tan(60/2)

RBC = 200 * tan(30)
RBC = 115.47

This means the circle area coverage is even smaller!

If the beam is a full 115.47 in length from end to end on the bottom, then the radius is 115.47 / 2 = 57.87.

Area of a circle is = (pi)r^2

A = (pi)57.87^2
A = 10521 square feet

In square miles, that's now: 0.00037738895

159 / 0.00037738895 = 412315 scan areas.

now we're at 4.1 million lake trout, lol. I bet I'm overestimating the number of square miles they might be in.

That sounds a bit crazy. But MNR did stock 100k lake trout in 2021: https://www.lioapplications.lrc.gov.on.ca/f...ne&locale=en-CA

90% of the fish are in 10% of the water.

Anyway, 20 degrees are not rock solid cut angle in the water, it is defined by manufacturer the angle in which software can reliably process the scan echo results and interpret them at average sensitivity.
The scan angle for every fishfinder is kind of soft one, increasing the sensitivity of the data processing, you are actually increasing and sensitivity to see way outside those 20/60 degrees of your "preset" angle.
How many times did you see that suspended fish, say, showing distant blue on your screen turned to yellow while you are slow moving a boat and, obviously, the fish mark moved much higher? See the distance your boat travel at this time and calculate the angle needed to see that fish initially. So, as an example - if the mark showing blue, distant fish, at depth, say, 100 ft over 120 ft, and moving your boat some 20 meters you see that the mark raised to 60ft over the same 120ft, getting much closed to the center of the scan angle... Do your math...
This is one of the real examples from my observations on Hummingbird.

Absolutely correct IMO.

Lakers are stacked in areas right now and those areas are concentration of the total population. You can not accurately calculate a population based on what you see on your graph and how much available water there is.

Absolutely correct IMO.

Lakers are stacked in areas right now and those areas are concentration of the total population. You can not accurately calculate a population based on what you see on your graph and how much available water there is.

Lakers are stacked absolutely everywhere. I covered at least 5 x 5 miles over the weekend. From 70ft to 120ft.. stacked.

I couldn't find a spot unless it was less than 70ft where lakers aren't. Yes, in front of Friday Habour, down the bay, along whitefish alley, just outside the long shoal.. they are... everywhere.

I have some doubts those are lakers in reality...
Would like to ask my buddy to bring his camera next time to see who is lurking under the boat, suspending.

Did you get any laker from those suspended marks reelingthebigone? I also think these are not lakers. Either suspended wf/herring of a school of bait/ small herring. Something like panoptics/ active target will tell for sure.

Yes, I have hooked up those suspended fish. It's hard, but they do chase if you p### them off enough.

They have a large red return and aren't small. The only thing they could be is whitefish or lakers in my opinion.

My boat is pulled for the season, but I was thinking about lowering a gopro down with a light on a downrigger

Personally I catch more suspended lakers than bottom lakers on the soft water. I find the he suspended lakers way more active.

Bingo !


I have to agree totally, and will apply the same thought and observation to almost every shield lake I fish for trout

they suspend for specific reasons

lack of 02 on the bottom,

temperature

targetting food


I'm not saying lakers don't hug the bottom at certain times, but pesonally i normally find active feeders from 15 to 40 feet fishing inland lakes

Definitely agree! I do a lot of salmon and trout trolling on Ontario and a few times on Simcoe. If you find suspended fish they are active. I’ve got hours and hours of footage from go fish cam and water wolf. It shows how active they are. The fish on bottom negative mood fish but can be caught eventually if you “trace bottom”. If anyone hasn’t read and of Dan Keatons books I’d highly recommend it. Lots of great info in there, even for Lake Simcoe lakers.