What are these?

This is in the Willamette on the west side of Ross Island.  What do you think, sturgeon or something else? I'm pretty sure they are sturgeon due to the depth.

Sturgeon, walleye,catfish or smallmouth. Drop a jig and nightcrawler and you might find out.

Sturgeon.

Sturgeon

Yes those are Sturgeon.

Some of those arcs are even sturgeon shaped.

Definitely sturgeon.  Often times depending on location and current, Sturgeon will also show up at almost a 45 degree angle.  Their heads will be down sucking stuff off the bottom while their bodies are angled up.

Definitely sturgeon.  Often times depending on location and current, Sturgeon will also show up at almost a 45 degree angle.  Their heads will be down sucking stuff off the bottom while their bodies are angled up.

A sonar screen doesn't show a real-time picture of the entire area under a boat, and doesn't reveal whether a fish is hanging horizontal in the water or with its head down.  The sonar return from the current instant is shown on the right edge of the screen, and that return marches steadily across the screen from right to left. Depending on the speed of the display, the return from 5 seconds ago might be a quarter of the way from the right of the screen, the return from 10 seconds ago might be half way across the screen, and the return from 15 seconds ago might be three quarters of the way from the right of the screen.  So if if your boat is stationary and a fish return is low on the left and high on the right, that means the fish was rising.  If your boat is stationary and a fish return is high on the left and low on the right, that means the fish was descending.  If your boat is moving and the fish return appears as an arc which is high in the center, that indicates that your boat moved across a stationary fish.  When the cone of your sonar first hit the fish, it might be 45 feet away at 30 degrees in front of you.  As you pass directly over the fish, you might be only 40 feet away from the fish, so the arc ascends to that point.  After you pass the fish, the arc descends until the fish is 45 feet away at 30 degrees behind you, after which the cone of your sonar goes past the fish, and the return disappears from the screen.

+1. I think more of us would benefit greatly in our fishing from having a basic understanding of how Sonar works like pmmpete. Didn't Rawkfish just give a seminar on this at Next Adventure? Maybe a NWKA tutorial video would be useful......

Sonar images can be interpreted as simple blips and arcs (bait and fish) but there is a ton of information in a single image if you know what your looking at, even with an $75 FF. In the case of this image I'm just looking at the largest arc, because I'm after the big one when I'm on the hunt. To me it looks like a single large fish, stationary as pmmpete says, and it has a strong return in the body center. So it either has a big swim bladder or a big meal in it's belly, but it is a thick fish either way. I don't know much about Sturgeon and don't even know if it has an air bladder, and it doesn't matter here. I'm also looking at the position of the red area of that arc within the overall lighter colors of the arc to provide information on the orientation of this fish. The air bladder and stomach that give stronger returns (darker colors like red) are located closer to the head. Shape of the darker red area can tell me more about the species and this fish if I know the shape of the air bladder in these fish. Then I look at the scale of this fish. Is this smallmouth water, and if so are those smaller arcs smallies? They are likely 15" average size fish, then I can get an idea of the size of the fish I want to target in this image. Is my drag set right? Do I have the right size hook, leader, bait? It goes on and on and on. If your goal is to slam down the biggest fish available then the more you know about how to read the screen in front of you the more you increase your trophy-ratio.

Fishing is just luck right? Yeah, right.

Definitely sturgeon.  Often times depending on location and current, Sturgeon will also show up at almost a 45 degree angle.  Their heads will be down sucking stuff off the bottom while their bodies are angled up.

A sonar screen doesn't show a real-time picture of the entire area under a boat, and doesn't reveal whether a fish is hanging horizontal in the water or with its head down.  The sonar return from the current instant is shown on the right edge of the screen, and that return marches steadily across the screen from right to left. Depending on the speed of the display, the return from 5 seconds ago might be a quarter of the way from the right of the screen, the return from 10 seconds ago might be half way across the screen, and the return from 15 seconds ago might be three quarters of the way across the screen.  So if a fish return is low on the left and high on the right, that means the fish was rising.  If a fish return is high on the left and low on the right, that means the fish was descending.  If the fish return appears as an arc which is high in the center, that indicates that your boat moved across a stationary fish.  When the cone of your sonar first hit the fish, it might be 45 feet away at 30 degrees in front of you.  As you pass directly over the fish, you might be only 40 feet away from the fish, so the arc ascends to that point.  After you pass the fish, the arc descends until the fish is 45 feet away at 30 degrees behind you, after which the cone of your sonar goes past the fish, and the return disappears from the screen.

So.....that kind of info is amazing, especially to us less experienced users of electronics.  Are there videos or books that go into this kind of depth on FF?  Any chance you provide private lessons?      Thanks for that little lesson.

John

+1. I think more of us would benefit greatly in our fishing from having a basic understanding of how Sonar works like pmmpete. Didn't Rawkfish just give a seminar on this at Next Adventure? Maybe a NWKA tutorial video would be useful......

Sonar images can be interpreted as simple blips and arcs (bait and fish) but there is a ton of information in a single image if you know what your looking at, even with an $75 FF. In the case of this image I'm just looking at the largest arc, because I'm after the big one when I'm on the hunt. To me it looks like a single large fish, stationary as pmmpete says, and it has a strong return in the body center. So it either has a big swim bladder or a big meal in it's belly, but it is a thick fish either way. I don't know much about Sturgeon and don't even know if it has an air bladder, and it doesn't matter here. I'm also looking at the position of the red area of that arc within the overall lighter colors of the arc to provide information on the orientation of this fish. The air bladder and stomach that give stronger returns (darker colors like red) are located closer to the head. Shape of the darker red area can tell me more about the species and this fish if I know the shape of the air bladder in these fish. Then I look at the scale of this fish. Is this smallmouth water, and if so are those smaller arcs smallies? They are likely 15" average size fish, then I can get an idea of the size of the fish I want to target in this image. Is my drag set right? Do I have the right size hook, leader, bait? It goes on and on and on. If your goal is to slam down the biggest fish available then the more you know about how to read the screen in front of you the more you increase your trophy-ratio.

Fishing is just luck right? Yeah, right.

Definitely sturgeon.  Often times depending on location and current, Sturgeon will also show up at almost a 45 degree angle.  Their heads will be down sucking stuff off the bottom while their bodies are angled up.

A sonar screen doesn't show a real-time picture of the entire area under a boat, and doesn't reveal whether a fish is hanging horizontal in the water or with its head down.  The sonar return from the current instant is shown on the right edge of the screen, and that return marches steadily across the screen from right to left. Depending on the speed of the display, the return from 5 seconds ago might be a quarter of the way from the right of the screen, the return from 10 seconds ago might be half way across the screen, and the return from 15 seconds ago might be three quarters of the way across the screen.  So if a fish return is low on the left and high on the right, that means the fish was rising.  If a fish return is high on the left and low on the right, that means the fish was descending.  If the fish return appears as an arc which is high in the center, that indicates that your boat moved across a stationary fish.  When the cone of your sonar first hit the fish, it might be 45 feet away at 30 degrees in front of you.  As you pass directly over the fish, you might be only 40 feet away from the fish, so the arc ascends to that point.  After you pass the fish, the arc descends until the fish is 45 feet away at 30 degrees behind you, after which the cone of your sonar goes past the fish, and the return disappears from the screen.

Are there videos or books that go into this kind of depth on FF?

I'd also be interested in any videos, books, or web pages which provide detailed information about how sonar works.

For example, how does sonar display a sloping bottom?  It's easy to interpret sonar if your kayak is moving across a flat bottom.  But what does sonar show when you are moving across a bottom which slopes sharply from left to right? And what does sonar show when you move from shallow water into deep water, or the reverse?  Does it read the depth directly below you, or does it show an average depth?  For example, suppose you are moving across a steep slope and the bottom is 60 feet directly below you, but 30 feet deep off to your left, and 90 feet deep off to your right.  Does the sonar screen show the bottom at 60 feet, or the bottom at 40 feet?  Is there a lot of water column and fish which are hidden by the bottom return shown on the screen?

When ice fishing, you are (hopefully) stationary with respect to the bottom.  When fishing with a heavy jig, you can tell exactly when your jig hits the bottom.  When lowering my jig down to a sloping bottom, I have often seen my jig disappear into the bottom return quite a few feet before the jig hits the bottom.  So there could be a lot of fish right above the bottom which I can't see on my sonar screen because they are covered by the return for the bottom.  On the other hand, if I am fishing on a mound or high point, my jig usually hits bottom at the same time that its sonar return reaches the sonar return for the bottom.

So suppose I am trying to downrigger troll right above the bottom for lake trout. When the bottom is level, I can use my fish finder to run my downrigger weight within a couple of feet of the bottom.  But if the bottom is sloping from left to right, or the bottom is rising or falling, there may be more water beneath my downrigger weight than appears on the screen.  It may look on the screen like the weight is only three feet above the bottom, but the weight may actually be 12 feet above the bottom.  The only way to tell for sure is to lower my weight until it nicks the bottom, or I feel my lure catch on the bottom, which is risky because I could snag my weight or my lure.  If I knew more about how fish finders work, I could downrigger troll more effectively over a sloping bottom.

For example, here are a couple pictures I took of my fish finder screen when downrigger trolling across an underwater ridge.  The yellow stepped line is my downrigger weight. The yellow curved lines are lake trout which I passed over, and which may have risen up off the bottom and then dropped down to investigate my lure.  But because the bottom is sloping, the water is probably deeper directly below me than is shown on my sonar screen, so I should have been running my downrigger weight closer to the bottom return.

Here's a good resource...

http://doctorsonar.com/blogs/educational-articles

He also has books, DVDs, etc.. but I haven't checked those out yet.   I do however follow his Facebook page and he constantly posts various... "what is this?" type sonar questions and answers..

https://www.facebook.com/DoctorSonar/

Here's a couple links to some YouTube videos on the subject that are helpful:





This is from a British fishing show that's done on YouTube. It goes over some different units, and ways to make them portable and convenient. I've found out that the Brits are big into Kayaks and small boat fishing due to limited space of their country and their love of fishing. Some good info to be garnered by our beer appreciating friends!This is from TAFS:



Plus if you search your particular model of fish finder, someone most likely has done a video on it on YouTube. I personally like to look outside the "normal" channels information from time to time. This allows for getting new ideas on solving old problems!

Brian, thanks for the link, the man has some amazing info on his page. Shougal, thanks for posting the videos, nice info.

Thanks
John

I'll resist quoting here as its getting lengthy. But yeah CDAT if and when I can make it down to OR hit me up and I can do a class. This is what I do for work too. I'm an Oceanographer that works with a lot of bathymetry and fishing. So I've had a ton of training. I use it all the time in fishing and will be glad to pass it along. Perhaps I can find time to do a video on PNW fishing with sonar. I don't see much of that when I search YouTube University.