FCV-1150 with 200B-8B - sounding interpretation

Hi everyone.

 

I was going through my phone this morning and came across these photos of a spot i found a few months back and would love to hear some thoughts on interpretation of the sounding.  Came from a Furuno FCV-1150 and 200B-8B transducer.

 

I remember barely getting any enquries, and on one drift we picked up a Cobia and a Spangled Emperor, but then went quiet again.

 

I don't see this as hard bottom, and thought it was some rocky / coral structure on some softish bottom, with some fish swimming above and on the edge.  Or am i wrong and this simply bait schooled up close to the bottom.

 

Photos 1 to 3 are from one drift, and photo 4 is from a another drift.

 

Look forward to hearing back.

 

 

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ranmar850's picture

Posts: 2607

Date Joined: 12/08/12

I haven't used that model Furuno

Sun, 2020-07-19 10:30

 But can offer some general observations. Using 200hz according to the display?There are a few patches of much longer tails on the main picture, but was the boat rolling much? The way that they are broken up makes it look like it may have just been boat roll. or a tight turn to go back and look?  Easy to tell at the time, you feel the roll, see the longer tails. If, however, the boat was not rolling, that would indicate harder bottom. So you are driving across broken bottom of hard patches and sand. You probably understand this already. Bottom lock is very good at separating growth on the bottom from the bottom itself, but it looks to extend too far off the bottom to be coral? Normally you would expect coral/sponge growth to reach up no more than about 1.5 m on bottom lock, usually under a metre. When we were using bottom lock to set pots in deep water, you'd have your bottom lock dialled right down to the smallest range , maybe only 2 fathoms on some machines, or 2 metres if metric units selected.Looking for growth less than a metre high, to indicate live bottom, and hence, crayfish.  Certainly a high, dense bottom lock reading. I'd be sort of excited to get that. Right in the middle of the first picture, it actually looks like very much like deeply ledged and broken bottom, but the tails under it are short, so probably not. 

so, overall, maybe just very dense aggregations of small fish, with a few larger ones in attendance.

chevaps's picture

Posts: 38

Date Joined: 04/01/13

Thanks for your feedback

Fri, 2020-08-07 21:42

Thanks for your feedback Ranmar.

The first 3 photos are consecutive from the one drift so that i could show how the ground transitioned.  There was definitely some rolling of the boat because the conditions were getting rougher at the time, thus i didn't spend too much time there.

Based on what you've said, i'll take it as some broken ground with dense aggregations of small fish, and some larger candidates about.  Where there's small fish, big fish will defintley be lurking around.

 

Interesting comment on the identification of coral.  I think the next time i'm out i'll reduce the bottom lock to 5m, but recently i installed a sat compass with heave compensation so could make bottom lock redundant.  Still learning my way around using the heave compensation to my advantage.

 

I'm itching to go back to this spot and give it another crack and tempt some of the larger red blobs to take a jig or bait.