Notices
Like Tree3Likes
  • 1 Post By Seacraft25
  • 1 Post By NRGarrott
  • 1 Post By abbor

Shallow Water Fish in Bait Balls

Old 12-06-2017, 10:06 AM
  #1  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Jun 2013
Posts: 640
Default Shallow Water Fish in Bait Balls

When a fish is inside a bait ball most fishfinders seem to miss the fish. Why is that?

The top picture is what I want to see all the time, but this is the only clear example I can find. The rest are what I am talking about, where you lose track of the fish. These are all striped bass in the Chesapeake bay.
Name:  baitballhit.jpg
Views: 1027
Size:  72.1 KB

Name:  baitball close.jpg
Views: 1023
Size:  90.3 KB
This one is my shot, I think those are stripers inside the baitball, but you lose all definition.

Name:  Baitballmiss2.jpg
Views: 1013
Size:  63.1 KB

Name:  Baitball touch.jpg
Views: 1002
Size:  75.7 KB

Name:  Baitballmiss.jpg
Views: 1018
Size:  207.8 KB
NRGarrott is offline  
Old 12-06-2017, 12:32 PM
  #2  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 21,750
Default

Some aspects to consider.

Transducer selection is important...frequency and sensitivity of the ducer is a big factor.

Also..CHIRP or non CHIRP..

Some true CHIRP units do have a bit better target separation in some cases.

And there are also units like the Furuno that do very well with non CHIRP.

Many variables...

And considering the fact the best sonar return is from the swim bladder.....a fast moving fish chasing bait will normally reduce the bladder ...thus somewhat of a limited return that may not show up well in a bait ball of other massed targets...etc.
semperfifishing is offline  
Old 12-06-2017, 02:10 PM
  #3  
Admirals Club Admiral's Club Member
 
Join Date: Apr 2014
Posts: 611
Default

B175hw with evo3 I can see the striped bass on bunker schools no problem
Attached Images   
Seacraft25 is offline  
Old 12-06-2017, 04:36 PM
  #4  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Jun 2013
Posts: 640
Default

In the second picture you can. In the first....
NRGarrott is offline  
Old 12-06-2017, 04:45 PM
  #5  
Admirals Club Admiral's Club Member
 
Join Date: Apr 2014
Posts: 611
Default

Originally Posted by NRGarrott View Post
In the second picture you can. In the first....
I count 4, 2 right in the school 2 off to the side bottom left hand side, maybe you aren't actually marking fish it's just bait. With those images I posted there is no doubt in my mind that ball of bait had bass on it
Seacraft25 is offline  
Old 12-08-2017, 12:47 PM
  #6  
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 14,046
Default

SonarHub with B175H-W
Attached Images  
abbor is online now  
Old 12-09-2017, 12:00 PM
  #7  
Admirals Club Admiral's Club Member
 
Join Date: Oct 2010
Location: RI
Posts: 1,143
Default

Wow. That is F-ing fantastic. Great clear shot. Abbor, what unit are you running of Simrad? Evo 3? I have original NSS8 but will most likely upgrade down the road. That looks awesome!!


QUOTE=abbor;10909300]SonarHub with B175H-W[/QUOTE]
vman24 is offline  
Old 12-10-2017, 03:13 PM
  #8  
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 14,046
Default

I'm currently running two 12" units, one Evo2 and one Evo3. The screen shot is from last year before I upgraded to Evo3, so it's a SonarHub displayed on the original NSS12.
abbor is online now  
Old 12-12-2017, 03:42 AM
  #9  
Admirals Club Admiral's Club Member
 
Join Date: Sep 2015
Location: Mid Coast Maine
Posts: 223
Default

Assuming most people are using CHIRP, I agree with the above about transducer selection & settings being a large factor to see separation.

Another point to mention is how the fishfinder interprets what the transducer is sending it. Remember that the transducer cone is more of a 3d signal. What you see on the screen is 2d, so some of that information can get layered on itself showing a big blob. Just something to think about.
Bass Monkey2015 is offline  
Old 12-12-2017, 06:13 PM
  #10  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Jun 2013
Posts: 640
Default

Originally Posted by Seacraft25 View Post
I count 4, 2 right in the school 2 off to the side bottom left hand side, maybe you aren't actually marking fish it's just bait. With those images I posted there is no doubt in my mind that ball of bait had bass on it
Oh I agree, there is bass in that ball. It's the lack of seeing them I'm talking about.

Abbor why do you run the gain so high? Small fish?
iFishMD likes this.
NRGarrott is offline  
Old 12-22-2017, 07:33 PM
  #11  
Senior Member
 
Join Date: Apr 2015
Location: Southern Colorado
Posts: 350
Default

Semperfifishing,

Can you explain why or how the swim bladder gets the best return? I thought the hardest or most dense objects get the strongest return.?. The swim bladder is a thin air-filled sack, so what makes it give the best return? I will have to rethink how I interpret the images on my sonar, now.
malty falcon is offline  
Old 12-23-2017, 04:11 AM
  #12  
Senior Member
 
Join Date: Aug 2016
Location: Kalbarri, WA
Posts: 484
Default

And why do sharks show up so well? Sharks don't have swim bladders--I've always been sceptical of this swim bladder business.
ranmar850 is offline  
Old 12-23-2017, 05:09 PM
  #13  
Senior Member
 
Join Date: Feb 2005
Location: Norway
Posts: 14,046
Default

Originally Posted by ranmar850 View Post
And why do sharks show up so well? Sharks don't have swim bladders--I've always been sceptical of this swim bladder business.
It's a great idea to be sceptical towards physics theory, even if Newton told us why apples are falling down, how can we be sure they are always falling and not flying away

It's all about acoustic impedances for the different materials and reflections when the sound waves go from one material to another.

The flesh of the fish has a density and also an acoustic impedance very close to water and very little of sonar signal is reflected. The air bladder has a very different density and acoustic impedance and almost all sound waves hitting it will be reflected so a strong signal is shown even if the air bladder is small.

A shark has a lot of bones with higher density and acoustic impedance than water, even if the difference in acoustic impedance is much smaller than between water and air the huge amounts of bones in a shark will make a lot of sound waves reflecting back to the transducer.
abbor is online now  
Old 12-24-2017, 07:10 AM
  #14  
MemberCaptains Club Member
 
Join Date: Jan 2002
Location: Sandy Hook. NJ USA
Posts: 65
Default

If you're gonna get all scientific about it, sharks have cartilage, but good explanation.
Ltack18 is offline  
Old 12-24-2017, 08:18 PM
  #15  
Senior Member
 
Join Date: Apr 2014
Posts: 849
Default

Originally Posted by Bass Monkey2015 View Post
Assuming most people are using CHIRP, I agree with the above about transducer selection & settings being a large factor to see separation.

Another point to mention is how the fishfinder interprets what the transducer is sending it. Remember that the transducer cone is more of a 3d signal. What you see on the screen is 2d, so some of that information can get layered on itself showing a big blob. Just something to think about.
Actually the data from the transducer is a 1D stream of data, that the screen plots over time to appear as a 2D image to us.

It’s the same data (albeit a bit more resolution) as the old fashioned rotary flasher. Just presented a bit better.
Hossharris is offline  
Old 12-26-2017, 04:42 PM
  #16  
Senior Member
 
Join Date: Aug 2016
Location: Kalbarri, WA
Posts: 484
Default

Originally Posted by abbor View Post
It's a great idea to be sceptical towards physics theory, even if Newton told us why apples are falling down, how can we be sure they are always falling and not flying away

It's all about acoustic impedances for the different materials and reflections when the sound waves go from one material to another.

The flesh of the fish has a density and also an acoustic impedance very close to water and very little of sonar signal is reflected. The air bladder has a very different density and acoustic impedance and almost all sound waves hitting it will be reflected so a strong signal is shown even if the air bladder is small.

A shark has a lot of bones with higher density and acoustic impedance than water, even if the difference in acoustic impedance is much smaller than between water and air the huge amounts of bones in a shark will make a lot of sound waves reflecting back to the transducer.
I am not a "physics" sceptic. Apart from the fact that sharks have a cartilaginous skeleton, rather than bony, from my experience, it comes down to the sheer mass of the creature. Even the bony fish with swim bladders have a large variation in the size of the bladder vs body--the bottom dwellers have a much larger bladder than the fast-moving pelagics such as wahoo, probably due to the pelagics' need to rapidly change depth when hunting. Yet the wahoo, etc, still show up strongly, IMO.

I probably should give you some background, so you might appreciate where I am coming from. I was, for 26 years, a bluewater commercial skipper ( Americans would call me captain,we reserve that term for true ships masters) working the Western Rock Lobster industry , on the upper mid-west coast of Western Australia. We lived or died by our interpretation of sounder returns, and this was no bay or Florida lobster type fishery--it was open ocean, swell, and wind. A very windy coast indeed. When I started in 1979, we were still on thermal paper sounders--remember them? Furuno 850's were the best, then larger Furunos came along. The way we operated, out of our port, would probably intrigue you. Catching crays ( we referred to them as crayfish, not lobster) relied totally on getting on the right ground. Particularly important as you went further offshore--only a tiny fraction of the ground would produce. We largely operated with no first echo in sight--we would shift the range and zero to get the third echo in the middle of the page, and use that to see consistency of the bottom, but there was something else. We called them "dots"--it was obviously a 50khz interference that was present when crays were present. Whether it was the crays themselves responding the the blast from the 1kw transducer, or something else, we never knew , just that if you didn't get the dots, you got no crays. Transducers were fairing block mounted in hulls, and gave a lot of interference when it was rough, made it hard to sort dot from noise. This was pre-GPS days, so you couldn't just mark a spot and drive straight back to it. So you had the front door of the big Furuno open, breathing the smoke from the stylus on paper, watching, watching, for hours on end.
Then colour sounders came along, CRT jobs like the JMC V-11. Dots in colour were great. Others followed.And GPS came along. We were always early adopters, always looking for that edge in a highly competitive industry. We used to chase scale fish, too, sometimes during the season, sometimes in the off season. Back to a conventional picture on the sounder for that, still largely 50khz used. I can never recall seeing those fish as arches, although we were always looking for large schools of big fish, not individual returns. Interpretation of a sounder picture was an art that determined whether you succeeded or went broke, period.
Later on we went to keel-mounted transducers, after experimenting with drop down legs, much improved picture at speed and in rough weather. 200khz and bottom lock started to be useful--we found that growth showing on bottom lock, 200khz, always coincided with the "dots" in deep water, we were running two separate sounders to have one on 50 and one on 200. That, and GPS, made life a lot easier in the deep water well offshore, but the wind never stopped blowing.
I left the industry in 2005, I'd had enough. My echo sounder for the last four years or so was a Simrad EQ42, what a revelation. Split screen with totally independent controls for each side, brilliant picture. If you can find a picture of one now, they look archaic.

So the arches will only show on CHIRP sounders? I've been running a Lowrance elite-7 CHIRP on my little 18'6" trailerboat for a few years--I found the 83/200/455/800 transducer supplied very weak--I replaced it with a HST-DFSBL, which made a great improvement. But this is a non-chirp transducer, no arches. But I don't recall seeing them on the other CHIRP one either. I have a new, larger boat on order--I am still deciding on the electronics, and am leaning towards the Raymarine Axiom Pro for the primary display.

And to go back to the original question--I imagine it would be very dependant on the actual density of the bait ball involved--if it was a thin curtain of baitfish surrounding the larger fish, it would probably show separately. If it was right in the middle of a large dense, ball, I doubt if any sounder could discriminate it.
ranmar850 is offline  
Old 12-28-2017, 08:10 PM
  #17  
Junior Member
 
Join Date: Nov 2017
Posts: 1
Default

Amazing post ! Thanks Ranmar
Megalodon17 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread