Fish Finders and Thermoclines

[flyfish]

Right now, I'm trying to choose a FF. I'm down to either the Garmin 260 blue or Lowrance X88DF. I fish in a few areas where thermoclines are very important. In looking at these models, I've noticed that the Lowrance (or at least its simulator) will pick up thermoclines. Garmin says (on its website) that their FF's will pick them up.<br /><br />My questions are (1) what has been your experience in picking up thermoclines with a FF?<br /><br />and (2) any recommendations between those two FF's?

 

[ThomWV]

Re: Fish Finders and Thermoclines

Between those two I'd take the Garmin over the Lowrance, but then I'd take about anything over a Lowrance.<br /><br />I've had CRT fish finders that were great for thermoclines but that could not be seen in direct sun light. Right now I've got what is probably the best fish finder/transducer combination made for small boats, bar none, and I've never seen a thermocline with it. Go figgure.<br /><br />Thom

 

[Ralph 123]

Re: Fish Finders and Thermoclines

This may help <br /> Depthfinder report

 

[flyfish]

Re: Fish Finders and Thermoclines

Thom,<br /><br />If you don't mind me asking, what is that combo?<br /><br />Ralph,<br /><br />Thanks for your help. Very informative.

 

[Boatist]

Re: Fish Finders and Thermoclines

FlyFish<br />I have never seen a thermocline on my unit but then I never tried to see one either. I sure you would have to turn the sensitivity way up.<br /><br />Those simulator are nice but very misleading. Have you ever seen a place where there are big fish every place you look and all make perfect arches. Only place I have see that is on the simulators. Even if there were that many fish at a place fish move and that messes up the arch. Also not every fish is going to be right under the center of the transducer, some will be off to the side and they will not make perfect arches like shown on the simulators. If there really that many fish some where who would need a fish finder.<br /><br />My point is they are not real but more like a dream or maybe a sales pitch or paid programing.

 

[SATCHER]

Re: Fish Finders and Thermoclines

Flyfish<br /> I have a Garmin GPSmap 185 that shows thermoclines. I stumbled on it accidentally. Last summer we had some cold water settle on the reefs off of WPB FL. and it showed on my screen up 10 feet off the bottom. I spoke to some divers and thay verified exactly that. Since this discovery I have noticed more of these thermos at differant depths from time to time. <br /> JD

 

[flyfish]

Re: Fish Finders and Thermoclines

Thanks for all the help. Got the Garmin 240 Blue based on recommendations here and elsewhere. Also, it was a darn good price, which didn't hurt. It'll be ready for action next weekend.<br /><br />This is a great site.

 

[ThomWV]

Re: Fish Finders and Thermoclines

I'm sorry, I hadn't looked back at this thread in a while.<br /><br />I am using a Furuno FCV-582L matched up with a 1-kW Airmar model M260 transducer. The real key to this setup is the transducer. As I'm sure most of you all are aware a company called Airmar makes the transducers for the vast majority of fish finder's made and sold around the world What a lot of folks don't realized is that although many of those transducers look a bit different from one another and although there are the three mounting methods (Transom, Thru-hull, and In-hull) the truth of the matter is that they all share the same single 1.7" transducer element. The result is that their performance is really all about the same.<br /><br />The transducer I use has a single 2" element for its 200 kHz side. For the 50 kHz side it has seven seperate, but considerably smaller, transducer elements. It also has an internal diplexer so only a single cable is used. Its large, and so on a small boat like mine the Thru-hull mounting probably wasn't a good idea. I chose to use the In-hull mount version (which is really what it is optimized for). To give you an idea how large this beast is here's a picture of it, its mounting tank (the yellow thing), and its top cover plate right next to a standard Thru-hull.<br />

<br /><br />This is a transducer with a very narrow set of cone angles but that gives it much better discrimination and of course increased maximum depth. It wouldn't be much good in most fresh water though, because those cone angles are 6 degrees at 200 kHz and 18 degrees at 50 kHz. Where it really shines is in the Q factor, which is just 8 and 10 for 50 and 200 kHz respectively. The Q refers to the continued ringing of the transducer element both after emitting sound and when receiving an incomming sound wave. The ringing blocks out a very small bit of time and is what makes it impossible for most finder/transducer setups to really have good discrimination between closley spaced targets on the bottom. It is also what causes that red band right at the surface (first few inches to the first foot or so) that you can't see into. In a practicle sense what it allows you to do is much more accurately see bait and for us to spot Tuna, which have next to no sonar reflection at all.<br /><br />Thom

 

[flyfish]

Re: Fish Finders and Thermoclines

Nice picture! And excellent information. Thank you.

 

[18rabbit]

Re: Fish Finders and Thermoclines

ThomWV – it is my understanding (and please correct me if I am wrong with any of this here) the ring/short-ring or Q is a function of the power sent to the elements, like hitting a tuning fork. The more power (the harder the hit) the longer the residual resonance. With the 600w output of your Furuno, you should have an even better Q value for the 260 since that transducer’s spec is based on 1000w performance.<br /><br />How does the Q have any effect on your search for tuna? I thought it was only an issue in less than 3-ft of water. (Part of why lower pwr ff's are better in shallow water.) How does the Q have any effect on the discrimination of closely spaced targets at depth?<br /><br />I have never looked for tuna. What does a tuna look like on your finder?...and how do you do it? I was told (by a hardcore, seasoned transducer person) that they are more than hard to nail with sonar unless moving slow. Tuna do not have an internal air bladder like most fish so no air space for a return echo. They spend their whole life in a state of ‘sink or swim.’ When moving at 20+ mph, they whip right thru the sonar cone and show up as a spec that can be confused with other ‘stuff’ in the water. It was suggested a thermal difference (1/2 deg. ?) was an easier way to spot them.<br /><br />Thanks for info.

 

[Ralph 123]

Re: Fish Finders and Thermoclines

Every time I have ever found tuna it was by crapping my pants watching them jump 3ft out the water from seemigly all directions at once... what a sight

 

[ThomWV]

Re: Fish Finders and Thermoclines

As I understand the effect of ringing that for fish finding capability its the ring on the return echo that hurts you. It blurrs, if that word works, the ability to distinguish nearby targets, particularly those that are stacked up on top of each other. At least that's my understanding but I could be corrected in a heartbeat because I'm certainly no expert here. But that's on the technical side. On the experience side I'm probably pretty good. I've been doing this for a good while now.<br /><br />Anyway I was trying to figure out how to explain what to look for. I knew I didn't have any photographs of the bottom machine screen with good marks because when they are present we tend to be very busy.<br /><br />So, I got out the fish finder (its up to 20 here today so far and a half a foot of new snow) and I broke out some wire and got it running. I found something in the demo that comes close to what you look for. So let me try to explain it.<br /><br />Here's the picture:<br /><br />

<br /><br />Now, look at the mark just to the right of the center of the screen, a little below center too. Notice that its more of a blob than it is an arch and that its a good strong return. First off I'd look for that but maybe a little thicker and one level down in the red color shade. Now, much more importantly, do you see that green cloud below the mark? Well, that is what I'm really looking for, but more often it would be in a very light blue that shows an even fainter return. If there is any chance at all of seeing tuna that very faint return is about all you're ever going to get. Sometimes we'll see little puffs like that, but usually in the lighter blue return, just free hanging and I've always assumed it was several fish (tuna) in close proximity to one another. But when we can find a ball of bait and that green under it we will always mark the spot (for years that meant toss an orange bleach bottle with a weight into the water, now I just smack a button on the Radar) swing around in a great circle and troll around the spot. That is how one would look that I would expect will raise fish if they'll come up.<br /><br />I hope I'm describing this reasonably well.