Depth Sounders, Graphs, and Flashers

[John Bales]

Hi David, I might have been on shipshawana lake on that one but not sure. This lake has a very heavy thermocline in the summer at 8 feet. Yes this lake is only 17 feet deep and it does have a thermocline. Mr. Perry never said that to whoop a fall turnover to fish in 15 feet of water or less. During the fall turnover, the surface cools and sinks. We as fisherman should look at this as a changing condition. Where are the fish? Where ever conditions are more stable. What water is effected the most during this change? Obviously the shallows. Where are conditions more stable? The deeper waters. The fall turnover is a tough time of the year because of the changing water conditions. This starts from the first frost till around 39 degrees. Actually, our thermoclines are completely gone and this will happen when the water temps get down to around 45 to 50. And I am going to tell you that I can see the thermocline get deeper as the water gets colder by looking at it on the depth meter. The scientific proof might be that all the baitfish and adult fish are at what ever depth the thermocline is. They are as deep as they can go because thats where they want to be. The deeper the thermocline goes , the deeper the fish go. Catching the fish at that point becomes the proof. We follow them right down and right before the lakes freeze up, they are in and around the deepest water in the lake or the deepest water in the area being fished. This happens exactly this way year after year. These are my observations over years of being on the water. The fish are very predictable. They are always where conditions are most stable. John

[Fran Myers]

Josh,
I have been creating an responses about sonar. Standard vs Broadband Sonar, Sonar vs. StructureScan Sonar, target separation,...
Honestly with the talk to purchasing success I have been less enthusiastic about putting more work into it. But I have decided to put some links here so you or anybody else can read or not.

The links come from http://www.hightechfishing.com. Dr Bruce Samson isn't a Spoonplugger so his terms aren't always correct but he knows his sonar equipment. He's a good guy, I've met him, bought his DVD's, and gone to his classes. All I can say is that I have personally seen these same types of views and have similar sonar pictures of my own. Ultimately you will need to choose the best options for your comfort level. Don't let me or anyone else talk you into or out of some equipment.

While it's has been a rocky start, I love my full HDS-8 with StructureScan, Sirius Weather, etc system. I also LOVE my Vexilar Fl-20 and FL-18's flashers also on my boat. Did I catch more fish by buying this expensive toys in shinny boxes - NO. Adherence to the Spoonplugging guidelines, pursuit of bettering my Spoonplugging skills is what catches my fish. However, the shinny new box stuff helps me figure out the why the fish are there or not, faster.

To be honest I became addicted to creating my own depth sounder maps using various software. This is the biggest reason for my spending. But using Spoonplugging mapping techniques. I just collect my data from the unit, import it into my laptop and software then create maps I can put on chips and use in my unit. I don't just slowly go back and forth across a lake, I still do the straight line passes, and do all the hard work required to catch a fish anyone else does, whether they have a sounder or not.

Getting an Elite-5 DSI with GPS is a good choice. Nearly bullet proof in operation, less complicated, and cheap. There is a lot of things it doesn't do compared to the full HDS but I know it's an awesome unit.

So if you have more questions let me know.

Links:

Target Separation

http://www.hightechfishing.com/sonar_rocks.htm

http://www.hightechfishing.com/fishweedtree.htm

http://www.hightechfishing.com/bump.html

http://www.hightechfishing.com/dsbb.html

http://www.hightechfishing.com/hdsclarity.html


Limitations of Sonar

http://www.hightechfishing.com/dzf.html


BroadBand Sonar vs Standard Sonar (not StructureScan)

http://www.hightechfishing.com/83_200.html


BroadBand vs DownScan

http://www.hightechfishing.com/broadband.html

[The Fisherman]

Fran, thank you for the links. I really can't argue with you on not putting time into writing stuff on here about electronics when people love to criticize it. Thanks again, the other things I got were very very informative and a great read!

John,

Sorry for the delay in answering what you asked about the natural lake. I am assuming that you were asking me this? SO following the progression that you listed. The fish were gradually moving deeper, they were doing this for a variety of reasons. The most prominent being stable water conditions at and around the thermocline. Above and the conditions(changing temperature) and the falling of the water layers, they would die. Below, they have no reason to be deeper. From experience fish will only go as far as the are forced, and generally no further. Hence, knowing all the stopping points, (that's why I look for those boulders JWT) So we have followed the fish through the fall conditions of a turnover until the thermocline has disappeared. So I can assume that the water temp is somewhere between, well lets just say that the fish are now cold enough, so that they will locate themselves in the deepest water in the lake, or area depending on the size. Since we can use our electronics to see fish, and you see none of them that means that they are in another lake now, right? Kidding! I would take this as assurance that the fish are rather dormant and non-chasing. They are on the bottom, DIRECTLY ON IT most likely. From what I am learning about the electronics. If they were off of it a few feet then we may see them, since we don't they ain't off of it they are laying on it. My decision at this point, knowing what I do would be to cast. For northerns I would most likely go with a light jig on spinning equipment or possibly a heavy little george. Once again, weather and water determining I may go as far as a spinner bait. This would be worked just like a jig but with the illusion of speed thanks to the spinners. Very effective under the right circumstances. Something else now that I know how to read my graph, is that I would look at the bottom. Any density changes would represent to me a break. This could very well be the only thing that they have down there to guide them so I would attempt to locate it while fan casting the hole.

Not sure if that's what you were looking for John, perhaps more on the electronics side. I think that I would be in the right here on all facets, yes?

Thanks for the brain work guys,

Josh

[Steve Craig]

Interesting.......no comments on using Spoonplugging guidelines for hunting!

Just last week, I hunted with a friend from NJ.
First part of the week we had a bad front come through.
No animals called the first day after the front.
None called on the second day
Only a coyote and a fox called the third day.
On day 4, we cleaned up with 4 bobcats, 4 grey fox and several coyote called.
Plus various other critters that come when the caller is running.
3 Mule deer, 1 eagle, several hawks, 2 jack rabbits, and a bunch of different song birds.
I looked at the sky and told my friend that the fish were moving too!

Spoonplugging was my guide in locating,and calling and killing these critters.
I used modern technology to do the killing.

Thinking back on some of the comments made here, I can see no way I could have called in 109 Mtn. Lions in 11 years using a simple hand call.
It took Wildlife Technologies advanced E-Caller with lion vocalizations(made by using modern recording equipment) to do what i have done. And Bucks guidelines.

There are advances being made every day in our equipment. It is foolish not to take advantage of it.
And thats all I got to say about that!

[Fran Myers]

Not being a hunter I cannot fully appreciate the efforts you use to get your level of success while hunting. I do say that when I know you are coming to Chicago, I look more forward to hearing your stories about hunting than most peoples fishing stories. Especially about the mountain lions favorite snack - bobcats or the 20 million dollar snack in Big Horn Sheep on a mountain being decimated by the over population of predators. I giggle still about the wolves being called in and you leaping in front of your client's gun to keep from getting huge fines. Yep I remember most of what you said.

I was fascinated when you said the animals use structure, breaks, and breaklines - just like fish do. I think using Spoonplugging for predators must be harder because they use other senses that fish don't. But it never occurred to me that all animals behave the same.

I know from being told from Terry and John that when birds or animals are in an activity period so are the fish. I enjoyed the pictures very much. I wish I was a hunter but I am thinking seriously about coming for a visit to see your described method of getting stripers. I think that's my exact solution for a pike situation I am thinking about.

Anyway I found it very interesting Steve, thanks.

[John Bales]

Josh, I wanted you to continue to think about finding these northerns other than the cast. Where would you look next and why. You would continue to troll but where would you look and would you go out there beyond the base breakline when there is no visable features that you can identify? In what direction would you go if you went out there? What would you look for? John

[The Fisherman]

John, kind of a butt kicker here buddy! Cant see anything with lures? Nor with Electronics...hmmm...Well I have had a couple of times in AK where a situation similar to this arose. I knew nothing of the thermocline, didn't know my electronics, so once I could find no other breaklines or outstanding breaks I was reluctant to leave known structure. The problem was that I didn't want to wander off into deep water and not deep structure. The only way to solve the problem, not using the cast is to begin trolling passes. Parallel strait line passes beginning from the last known breakline. There are a couple different approaches for vertical depth control in this situation.

The starting point for me would be to use bottom bumping lures, in this case I would probably go wire with 100's and up. I would continue until I worked all the way across the lake to the other side of the hole and was back to 36'. If the area was simply to vast to do this efficiently then I would focus on working a little ways past the point where the water reaches its greatest depth. This process would most likely show me something, bottom change, muck, old tire whatever the break is, if my electronics didn't see it my lures would most certainly find it if it can be found.

The next step is the more difficult and easily messed up. With the last known stopping point being a 36' breakline, the fish may very well not go any deeper. This in most cases is sufficient water depth to keep them alive. I would get the line length correct and make the same passes that I made on the bottom. The fish may have moved out horizontally from the last breakline if they have then this will locate them.

Lastly and perhaps I would have done this first, is to troll the entire length of the 36' breakline. If the breakline ran all the way around the lake then I would go all the way, if the lake was small enough. If to big to do this then I would work the 36' breakline in areas nearest to the structures. With the fish not being seen on the graph, they are once again likely to be dead on the bottom. If all deeper water is literally void of all breaks then the fish would not go any deeper. Unless there is a water condition that they can see or feel that I cannot. So working the last spot that they would have a sign post and a few feet deeper, you would effectively cover every where they could be that you can pinpoint them.

If after all this there were no fish located, there is one answer. They are not there. They can see something that I haven't found. Then I would go back to the cast on the deepest known structures in the lake. Exercise patience and eat a peanut butter sandwich However, my patience will get very short. I will for sure find myself repeating the above procedures until the fish become active or I find a deeper break.

Josh

[John Bales]

Josh, Have eaten many of peanut butter sandwitches while learning. In the middle of the day when a man is starving, they taste like steak. The key word is depth. If you ever run out of guidelines and you have yet to check out in and around the deepest water, this is your last step. If I were to say it sientificly, Let depth be your guide. I know that Jerry borst has caught tons of northerns in this situation that are so far away from anything that you can see or feel, you would think at first, they are out in the middle of no where. If you go out there and just look, if the fish are not much active, you will see very little on your graph. If you happen to be there and see some baitfish that are close to the bottom, you are getting warm. Once you catch the fish, you will see that there was something there. A slight turn at a certain depth, the end of a hole where it may gradually start getting a little shallower but still far away from anything or the absolute deepest water period will have all of the fish. The late fall(right now for us till ice up) will be the time of the year that this takes place most often, although in many situations, it occurs a lot. I wanted to make you think. Most do not carry their depth control deep enough, especially when they run out of something to guide them. For most, waiting for the fish would be the right thing to do. There are some situations when the deepest water is not so large an area that can be a hay day when found. Some deep sections are so large that it is like looking for a needle in a haystack. I leave those alone unless there is a lot of time to spend on it. Most of the giant musky in the detroit river came from areas like I have described. A current break(but very deep), a small hole deeper than the surrounding area(smack dab in the deepest part), most of these spots were out in the middle of the river where no one has ever checked. Once a man has found such a place, you will surely have them to yourself and they have not been disturbed. John

[jwt]

Thanks John. Very enlightening.

[The Fisherman]

John,

It seems strange that we would find fish in the middle of no mans land, yet like you said its not. That is a similar idea that I was trying to communicate in another thread. As well as a reason that this one and our electronics can play a vital role. All in its own right. Fish will never be blind, this we know. Strippers in GA have a tendency to move horizontally from a river channel breakline rather than deeper. Why I can only imagine is something to do with current. Either way its just an example of a different way to go about depth control. While staying on the bottom is vital, it is also important, if you can, to check horizontally from deeper breaklines to ensure that fish are not suspended. Thanks again for the teasers John. Also is there any other procedure for depth checking outside visible guidelines that I didn't mention before?

Josh

[Steve Craig]

John,
Would I be correct in saying that the same situation exits in a Reservoir, at the "channel within the channel"?

Steve

PS. We just got hit with our first severe cold front of the fall here. Bad one with a 25 degree temp drop. Looks like we will be heading for the steep deep sides of the bends after this front, until February.

[The Fisherman]

Steve,

Enjoy the winter movements! When you talk about the channel within the channel topic are you speaking about the structure situations that exists within the channel itself? I have spent quite a bit of time working only the river channel from the top breakline down to the middle. The humps, bars, cuts and wash's that the original current created can hold some monster schools of all species and big fish in the schools. Not at all trying to steal Johns answer, just wandering if thats what you are talking about. Some seem to forget that the river itself used to contain fish and its own structures, similar to having an old pond that was flooded over when the reservoir was built. A lot of times fish will never leave these areas, they lived there before and now its even more stable. Plus they might never know that anything else exists in some situations. Can be some of the best structures in the winter months and bad cold fronts in the summer/fall.

Wow a 20+ degree temp drop, fish gonna love that Steve!

Josh

[david powell]

Question for the guys that went to kentucky lake.Did it have a thermocline.
Question for Josh You stated in response to John.
The fish were gradually moving deeper, they were doing this for a variety of reasons. The most prominent being stable water conditions at and around the thermocline. Above and the conditions(changing temperature) and the falling of the water layers, they would die.
What do you think would kill the fish.The lake temp was changing gradually they have plenty of food and oxygen,so what killed them?
THERMOCLINE?
A thermocline (sometimes metalimnion) is a thin but distinct layer in a large body of fluid (e.g. water, such as an ocean or lake, or air, such as an atmosphere), in which temperature changes more rapidly with depth than it does in the layers above or below.So as we can see actually at the thermocline the water is not stable.
Thermoclines can also be observed in lakes. In colder climates, this leads to a phenomenon called stratification. During the summer, warm water, which is less dense, will sit on top of colder, denser deeper water, with a thermocline separating them. The warm layer is called the epilimnion and the cold layer is called the hypolimnion. Because the warm water is exposed to the sun during the day, a stable system exists, and very little mixing of warm water and cold water occurs, particularly in calm weather.

One result of this stability is that as the summer wears on, there is less and less oxygen below the thermocline, as the water below the thermocline never circulates to the surface, and organisms in the water deplete the available oxygen. As winter approaches, the temperature of the surface water will drop as nighttime cooling dominates heat transfer. A point is reached where the density of the cooling surface water becomes greater than the density of the deep water, and overturning begins as the dense surface water moves down under the influence of gravity. This process is aided by wind or any other process (currents for example) that agitates the water. This effect also occurs in Arctic and Antarctic waters, bringing water to the surface which, although low in oxygen, is higher in nutrients than the original surface water. This enriching of surface nutrients may produce blooms of phytoplankton, making these areas productive.

As the temperature continues to drop, the water on the surface may get cold enough to freeze and the lake/ocean begins to ice over. A new thermocline develops where the densest water (4 °C) sinks to the bottom, and the less dense water (water that is approaching the freezing point) rises to the top. Once this new stratification establishes itself, it lasts until the water warms enough for the 'spring turnover,' which occurs after the ice melts and the surface water temperature rises to 4 °C. During this transition, a thermal bar may develop.

[david powell]

One more question,how does a depth finder show the thermocline.A depth meter is sonar, it sends a sound wave down then when it hits something the signal bounces back to the unit. The amount of time the sound wave travels tells the depth.Since the thermocline is simply a changing water tempature,there is nothing soild for the sound wave to hit . Some may say it is because the thermocline water is denser,true it is denser than the top layer,but the bottom layer is denser than the thermocline.So how can a depth meter pick up the thermocline.

[Steve Craig]

I didnt see a thermocline on either Kentucky or Barkley. I didnt expect to either.
Where there is current, you will not see the thermocline for the most part.

Here is a few pics of thermoclines:
http://www.angeln.de/praxis/echolote/lc ... est-report

Here is what Hummingbird says about the TC.

Thermoclines.... Some fishfinders also show thermoclines, which are the "fronts" where warmer waters intersect with cooler waters. Typically, the water is colder as you go deeper and certain fish prefer certain temperatures. The change in water temperature causes some of the sonar signal to reflect back creating a line across your screen at the depth of the thermocline. Identifying thermoclines brings you one step closer to catching the fish you're after.

Find the Thermocline using your Sonar Fish Finder

The dog days of summer are here and one of the most important things to know about your lake or reservoir is the depth of the THERMOCLINE. Find the thermocline and it will be much easier to find the fish.
What is a thermocline?

On calm lakes and reservoirs with little if any water movement, the water often stratifies and settles into two distinct layers. The upper layer is warmer, brighter (light) and less dense than the cooler, darker and denser water below. Once the water becomes stratified, there is very little movement of water between the two layers. The dense cool water near the bottom of the lake does not get any oxygen and becomes more and more oxygen depleted as the summer wears on.

Between the warm upper layer and the cold lower layer is a thin layer called the thermocline. The water in the thermocline is cooler than the upper layer and warmer than the lower layer. The light penetration and oxygen level in the thermocline are also improved.

In most lakes the thermocline develops somewhere between 15-25 feet deep. The depth and thickness of the thermocline can vary from place to place on the same body of water, and some areas of a lake or reservoir may not show a distinct thermocline at all.
Why do I care about the thermocline?

The thermocline is important when trying to locate fish because it is the depth that is most comfortable for the fish. The thermocline is the comfort zone for the fish because it contains the coolest water that has abundant oxygen and prey. The light penetration at the thermocline level is also improved. Most game fish (bass, crappie, catfish, walleye, trout, salmon, etc.) will be found near the thermocline, especially during hot summer days. Fish will rise into the upper layer at times, but most fish will not spend much time below the thermocline due to the lack of available oxygen.

When you find the thermocline, you should start your search for fish near that depth. Look for brushpiles, timber, humps, channels, points and other cover at or near the thermocline. If you sink your own cover (brush piles, condos, etc.), you should consider the normal thermocline depth for that lake and sink the structure near that depth (keeping in mind the normal summer depth of the lake or reservoir).

Pay close attention to where you catch fish in relation to the thermocline. Some species may prefer to be slightly above the thermocline while others prefer to be just below it. The time of day, brightness and other conditions also have an effect, so keep these things in mind when you are trying to pattern the fish.

Even catfish, known for living near the bottom of the lake, are affected by the thermocline. They will stay near the thermocline and will not spend much time below it. You might find huge concentrations of catfish in the middle of the lake suspended at the depth of the thermocline. They might be suspended at 20 feet in 40 feet of water.
How do I find the thermocline on my fish finder?

There are two ways to find the thermocline with your fish finder. The first way is to pay attention to the depth where you see the majority of the fish. That depth is probably the thermocline. The second way is to adjust your fish finder to show the thermocline depth on your graph. A quality fish finder will be able to detect the change in water density at the thermocline and will show you exactly where it is. Get into open water that is at least 30 feet deep or so and turn up the sensitivity (gain) of your fish finder sonar unit (above 80%). You should be able to see a fairly distinct line at the depth of the thermocline. If you are running your fish finder with fish symbols turned on, you will probably see a clean line of fish symbols at this depth.

If you can’t find the thermocline with your fish finder sonar, you can slowly lower a temperature probe and look for a fairly dramatic drop in temperature (3 or 4 degrees). That should be the thermocline.
What happens when the lake “turns over” in the fall?

In the fall, the upper level of water begins to cool off when the overnight temperatures drop. When the warm water in the upper level cools enough to become denser than the water below, the lake “turns over” and the layers mix together. This is a dramatic and traumatic event for the fish and the entire lake. Fishing is usually poor for a week or two as the fish adjust to the rapidly changing water conditions.