Red blobs

[Turner9087]

I am new to electronics on a boat and I was wondering if you could tell me what these are

[CenCal fisher]

I would put my money on a fish. When I see something that isn't connected to the bottom that doesn't look like interference, I call it a fish. I'll make a cast depending on the depth and surrounding structure. Fish only look like arches if you are moving and they aren't or you are still and they move through your sonar cone. Sometimes they are streaks on the sonar, solid lines if you are stirring still and so are the fish or blobs like you have.

 

i think fish might show up as blobs if you catch them on the outer edges of your sonar cone. My understanding of how sonar works is that the sonar is emitted as a cone from the transducer. A fish forms an arch when it passes through the entire cone because as it enters it is picked up at the edge of this cone. If you measure from the transducer to the edge of the cone it will be a further distance than from the transducer straight down. This is the first downward side of the fish arch. As the fish nears directly below the transducer the arch rises because the distance to the transducer is decreasing. As the fish moves away from below the transducer the distance increases and the arch slopes down until the fish is out of the cone. The fish is always at the same distance from the surface but your graph shows the distance from the transducer. If a fish just clips the outer edge of the cone it would appear at one depth and make a blob. This could be a single fish at the fringe of your transducer cone that just clips the cone twice to make two blobs

 

I'm probably not 100% accurate with how fish images relate to sonar and I'm sure a more educated and experienced forum member could correct me. Some of what I wrote might confuse you because I wrote it from my phone and didn't want to spend half an hour typing everything up in detail. I can try to clear up and questions you might have

[Turner9087]

I figured that's what it was but like you said I'm used to arches

[FreddoB]

The arches occur when you are moving over the fish as the return gets stronger and then weaker (from what I've heard and read). All the same, I too say "fish".

 

Did you catch it?

 

Best - FreddoB