duncan Posted March 24, 2006 Report Share Posted March 24, 2006 not met much weed or many rocks with swim bladders but they show up fine................ Quote Link to comment Share on other sites More sharing options...
markee_b Posted March 24, 2006 Report Share Posted March 24, 2006 Think he was implying the signal passes through the fish (except the swim bladder that it bounces off)...clearly this ain't gonna happen with a rock...with weed it's difficult to see his logic Quote Link to comment Share on other sites More sharing options...
toerag Posted March 24, 2006 Report Share Posted March 24, 2006 If my experience is anything to go by, sharks don't show up on fishfinders. Well, the one that did this didn't! :- This was also on a wreck in the deep, it ate half a cod as well. I also believe that FF are best used to showstructure, I can catch fish off a wreck all day long and not see anything on the sounder. Having said that, both my sounder transducers are mounted inside my hull, so I don't get the best out of them. Quote Link to comment Share on other sites More sharing options...
Fugazi Posted March 24, 2006 Report Share Posted March 24, 2006 It Quote Link to comment Share on other sites More sharing options...
crazy fred Posted March 24, 2006 Report Share Posted March 24, 2006 i must admit my sounder is selfish it tells me sod all or did you say shellfish!! Quote Link to comment Share on other sites More sharing options...
Adam F Posted March 24, 2006 Report Share Posted March 24, 2006 This guy is American, right? So they are led by a bunch of guys that can see weapons of mass destruction that aren't there, so why be-grudge the poor sap for seeing a sturgeon that probably wasn't there either? One only has to watch any American sports commentary or Sports program to see that they can not communicate without ridiculous hyperbole, the poor dears do get overexcited like 10 year olds at a fun fair Mad Mike - our very own stand-up!! Absolute quality.! Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 24, 2006 Report Share Posted March 24, 2006 I'm amazed by the suggestion that sharks do not show up on fish finders because of the lack of a swim bladder. Granted, the swim bladder in a fish does give a stronger return because of the air pocket, but the main body of a fish should also show up but as a weaker return. A shark's body would still give a return but without the stronger return in the middle caused by the swim bladder. If you do see a shark on your FF with a stronger return in the middle it will probably be a number plate or a diver's air bottle, in which case it's probably time to get a bigger boat. BF ps - this has intrigued me, so I might try to research it more. Quote Link to comment Share on other sites More sharing options...
Newboy Posted March 25, 2006 Report Share Posted March 25, 2006 The still remember the scene in Jaw which the shark started to gobble up the boat.... Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 25, 2006 Report Share Posted March 25, 2006 Done a bit more digging into this... The theory is that fish flesh is made up mostly of water, therefore there is insufficient difference in the substance that the sound pulse is passing through (from sea water to fish flesh) to cause a reflection. The swim bladder is filled with air and therefore presents a big change in the type of medium that the sound pulse passes through (sea water to air) and so creates a strong reflection. So, it is indeed the swim bladders that we are seeing when we detect a fish on the FF. The swim bladder of an individual bait fish is too small to be detected on its own, but a shoal of bait fish will be detectable. But I'm still not sure if a large shark will show on the FF. I guess the main body consists of mostly water, but what about the cartilage and jaw bone. Isn't cartilage and bone a honeycomb structure and therefore contains air?? BF Quote Link to comment Share on other sites More sharing options...
Fugazi Posted March 25, 2006 Report Share Posted March 25, 2006 Bob, When it comes to big sharks, the answer is you "NEVER" see the one that gets you. Quote Link to comment Share on other sites More sharing options...
duncan Posted March 25, 2006 Report Share Posted March 25, 2006 I think you will find the sensitivity of modern units has moved us on from these issues............. Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 26, 2006 Report Share Posted March 26, 2006 I tend to agree, Duncan. I have a recording of a shoal of bait fish under which are 3 or 4 larger individuals. In those larger fish you can clearly see the swim bladders high lighted in red and surrounded by the main body of the fish, which suggests the FF was detecting the flesh of the fish even if the return was weaker. My old plotter never showed this sort of detail. BF Quote Link to comment Share on other sites More sharing options...
Afishionado Posted March 26, 2006 Report Share Posted March 26, 2006 I think you will find the sensitivity of modern units has moved us on from these issues............. It is amazing the world we live in. How long ago would the stuff we have on our fishing boats been on the secret list and installed in naval craft? I remember the first Seafarer rotating LED ones which we thought were the last word in technological advancement. I understand that these days there are sets that can scan forward of the boat and show a three dimentional view of what the boat will (not has) cross over. Incredible! Mad Mike Quote Link to comment Share on other sites More sharing options...
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