Here’s a little story about the last fish I got this season, along with a couple of questions about what I was seeing on my sonar. My sonar doesn’t have screen capture, so I just sketched what I remember seeing.
It’s late November at Ovid, and there’s a fair amount of ice on it. I’m working shallow weeds close to the spillway, where the ice only comes out a few feet from shore. My boat is heading into the wind, parallel to shore. Eventually I come to a large patch of ice that forces me out into deeper water. I take a glance at my sonar and I see this:
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
"><link_text text="[Permission to view this media is denied] … bottom.jpg">[Permission to view this media is denied]
” alt=”
"><link_text text="[Permission to view this media is denied] … bottom.jpg">[Permission to view this media is denied]
” />
Hmm… could that be a fish on the bottom? [smilie=confused.gif] I figure it’s worth a cast, so I stop my trolling motor and grab my Bulldawg rod. At this point I’m maybe 20’ past the thing on my sonar, so I sling a dawg out about 40’, let it hit bottom and then start a slow, bouncing retrieve. By now the wind is pushing my boat back towards the object. When the lure gets close to the boat, I do a figure-8 and see absolutely nothing. Well, it was probably just a log on the bottom, right? So I go to turn my trolling motor back on, and I see this on the sonar:
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
"><link_text text="[Permission to view this media is denied] … g_arch.jpg">[Permission to view this media is denied]
” alt=”
"><link_text text="[Permission to view this media is denied] … g_arch.jpg">[Permission to view this media is denied]
” />
Holy @#$%&!, no doubt what THAT is! 😯 Visibility is about 3’. That fish was either hiding under the boat, or it was just deep enough where I couldn’t see it. A few seconds later, I see this on the sonar:
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
"><link_text text="[Permission to view this media is denied] … _lines.jpg">[Permission to view this media is denied]
” alt=”
"><link_text text="[Permission to view this media is denied] … _lines.jpg">[Permission to view this media is denied]
” />
Looks to me like that mother is heading back to the bottom. Out goes the dawg again, same drill, but this time I see the fish following close to the boat. I try increasing speed on the figure-8, but no joy. The fish disappears. I switch to a slower, jigging kind of figure-8 with more vertical motion, and the fish reappears, fading in and out of sight at the 3’ depth while maintaining interest in my 8’s. We keep up this dance for what must have been at least a minute, with me just catching glimpses of the fish as it turns the corners. Whenever the bait comes up shallower, the fish drops out of sight. It just refuses to come up into the light where I could get a good look at it. Eventually I lose sight of it for quite a few seconds, so I drop the dawg down to 5 or 6’ and do some straight vertical jigging. Then I pull it back up to 3’, give it a couple of bounces and WHAM! Less than 10 seconds later, the 37 incher is in the net. Not a big fish, but it was a fun way to wrap up my season. [smilie=biggrin.gif]
Now, on to the questions.
What does a muskie on the bottom look like on sonar? Was that thing in the first sketch the muskie, or was it a log or something like that?
In the 3rd sketch, there are a bunch of short lines trailing the arch and going down to the bottom. Are those faint sonar returns from the fish heading back to the bottom?
Great story!! That is awesome and I love the sketches accompanying it. In my opinion all of the things you are thinking you observed are absolutely correct!
First thing to keep in mind about the arch shape and other depictions of sonar- ok, we know that your sonar sends a cone shaped field of sound impulses, and the picture displayed is simply a representation of the timed responses (echoes) received from everything the sound waves hit in the water. The leading edge of your sonar is showing the instantaneous average of all the echo readings received, the rest of the screen is just the history of those readings. ok. If your sonar/boat is stationary, and you have a nice musky suspended under your boat, the graph is going to show a straight line for the fish because it is getting the same continuous readings. Add motion, lets say to the boat not the fish, and that flat echo will change shape into an arch because you are changing the distance b/w the sonar and the fish. From within your sonar's cone field, as you move closer to the fish the sonar thinks the fish is getting shallower, because the distance is shorter, even though in reality the fish stayed at the same depth. The highest point in the arch the sonar is closest to the fish, then it starts to drop down "deeper" as the sonar moves away from the fish but still w/n the cone.
Keep this in mind and you can interpret your sonar easier
Good explanation Duke.
Slinger – That is a fish in your first illustration because the fish isn't part of the bottom. A log would be a bump on the bottom with no separation.
Also, note the water temp. Remember that comfort is key and when oxygen is mixed throughout the water column temperature and light are the only comfort factors. The water on the bottom was three degrees warmer than the surface temp you note on your illustration.
"Duke" said:
The fishing geek should NOT have to explainthis one to the chemistry dork!!! So lets just let Hemi think about this one for a while… or maybe go ask one of your students for help on this problem!! sorry Tom, only having fun but you deserve a ration fopr this one!
DOH! Even I'm not THAT stupid! 😀
He didn't say, "warmer"; he said "[size=150]3 degrees[/size] warmer".
What I wanna know is, has he measured the temp with a probe? Did he implant temperature transducers in the fish he's caught? Did he swim down and measure it with his BBQ thermometer? Or has he simply recalibrated his x-ray vision for the thermal IR? 
"hemichemi" said:
He didn't say, "warmer"; he said "
[size=150]3 degrees[/size] warmer".
Of course, what else would I say?
Slinger specifically has 36 degrees on his illustration. I could be wrong though because Slinger's graph temp reading might be wrong.
Still waiting for your rebuttal in the "making scents" thread.
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
"Will Schultz" said:
[quote="hemichemi"]
He didn't say, "warmer"; he said "[size=150]3 degrees[/size] warmer".
Of course, what else would I say?
Slinger specifically has 36 degrees on his illustration. I could be wrong though because Slinger's graph temp reading might be wrong.
Still waiting for your rebuttal in the "making scents" thread.
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
87.3% of all statistics are made up on the spot. 🙄
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
Caught a walleye running over these
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
Saw lots of fish in 50 FOW..
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
">[Permission to view this media is denied]
” alt=”
">[Permission to view this media is denied]
” />
I usually catch fish when the fishfinder has been blank 😛
Thanks for the great responses, guys! 😀 I was careful to show the separation between the fish and the bottom in my sketch because it was very clear on my graph. What I couldn't interpret was the fact that it showed up as a very straight line, with no lower leading/trailing edges. In other words, no arch.
"jasonvkop" said:
I would think that fish seen on the fish finder arent caught a lot unless an angler is trolling or vertical jigging. The fish finder shows whats under the boat so one isnt going to see a fish caught way out on the cast.
Slinger's sonar transducer is on his trolling motor up in the bow, so he might see a fish which then moves to the side as his boat goes over it, maybe to a spot which is accessible to casting.
"Slinger" said:
What I couldn't interpret was the fact that it showed up as a very straight line, with no lower leading/trailing edges. In other words, no arch.
For some reason the distance b/w fish and sonar did not change much relative to your boat's motion. Likely your sonar cone just briefly clipped the musky on the lateral edge of its pattern, so it did not pass directly under the boat. The second time you saw the fish it went right under the sonar and was moving, giving the sonar more readings over the maximum sector length of of the cone. Make sense? A chalk board visual would be great here!
"Duke" said:
For some reason the distance b/w fish and sonar did not change much relative to your boat's motion. Likely your sonar cone just briefly clipped the musky on the lateral edge of its pattern, so it did not pass directly under the boat. The second time you saw the fish it went right under the sonar and was moving, giving the sonar more readings over the maximum sector length of of the cone. Make sense? A chalk board visual would be great here!
Yes, it DOES make sense! 😀 Something like this for the first time (arrow indicates direction of boat travel):
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
"><link_text text="[Permission to view this media is denied] … sonar1.jpg">[Permission to view this media is denied]
” alt=”
"><link_text text="[Permission to view this media is denied] … sonar1.jpg">[Permission to view this media is denied]
” />
and this the second time, when I saw the big arch:
"><url url="[Permission to view this media is denied]<url url="[Permission to view this media is denied]
"><link_text text="[Permission to view this media is denied] … sonar2.jpg">[Permission to view this media is denied]
” alt=”
"><link_text text="[Permission to view this media is denied] … sonar2.jpg">[Permission to view this media is denied]
” />
57
21