Fish Finder Tips & Information

Question: My Lowrance depthfinder never picks up any signs of a bass. I go to Lake Castaic in Southern california and bring the depthfinder every trip. I connstantly look a it and never see a single fish. Anyone know why it is not working properly?

Answer: It depends a lot on the quality of machine you have, the speed at which you're running and the sensitivity settings ... if you get a low cost unit like a $100 unit then it's not gonna work very good ... the more expensive units work a lot better and I depend on mine a lot ... I have a 334c igps lowrance and it's great for finding fish and baitfish ... if you have a cheap unit there's not gonna be much you can do with it other than telling what depth you are at and seeing little fish symbols which don't tell you anything ... if you can ... turn off the fish symbols and resetting it to factory default settings might help. the sensitivity works best for me set on automatic so that it automatically adjusts to your speed and all that ... usually around 75% to 80% is about where it auto adjusts to when I'm moving at about 4mph ... when it's running on plane it'll auto adjust to 100% so that it can maintain contact with the bottom while you're running so that you can see the depth and it'll show fish when you're running wide open as well but you can't tell anything about the fish you're seeing when you're running wide open or on plane because the boat is moving too fast to show arches and it usually just shows up as jumbled up looking mess on the screen when there's a lot of baitfish in the area but if I slow to 4 mph or slower then I can tell pretty much what's under the boat ... whether it's scaley fish or if it's catfish or baitfish.... catfish will show up as more yellow looking ... scaley fish are red and blue as they send back a stronger signal or harder signal than catfish do ... when you're going over soft mud you also see the bottom as yellow and then deeper into the mud is red and even deeper into is like 7 or 8 ft comes back as blue or black ... since catfish don't have scales they look like the soft mud and return a yellow arch but mine is a color unit ... you can't tell much about what species of fish they are when using the regular black and white led kind.

When you're moving the speed of the boat predicts how big the arches are ... like if you're going 1 mph a little sandbass might look pretty big but you can pretty much tell how big the fish is by the thickness of the arch too ... if it's a thin arch then it's a smaller fish ... if it's a foot thick or so then it's a big fish. when using fish symbols you don't get to see the raw data that's being returned so you can't tell too much about what's down there by using the fish symbols. but here's how I tell how big the fish are ... if not going by the thickness ... I watch the fish finder and when the arch starts showing up I try to see how much the boat has moved in conjunction with how long it takes to go over the fish ... like if the arch starts showing up and you've moved 2 ft across the water and that's the end of the arch then the fish is around 24" long ... if you've moved 4 ft and the fish arch takes that long to complete when you've moved 4 ft then the fish is a lot bigger and going by the thickness also gives you a little bit of an idea how thick the fish is and how long they are ... so if I move over a fish and it's about 4 ft long and returning a red/blue arch and it's only about 6" thick then chances are that's a gar .... gar are really hard and have thick scales and dense skin so they return a red and blue arch and if they're about 4 ft long and just 6" thick then I know it's a long skinny fish with hard scales .... now if I move over a fish that's 3 or 4 ft long and returns a yellow arch and is about a foot thick then I know that's a catfish that's somewhere around 20 to 30 lbs possibly but what I'm actually looking for when I choose a place to fish is the shad or baitfish and I look for busted up shad ... if there's just a lot of shad in tight formation then I know there's not anything messing with them and there's no fish in the area ... but if I find busted up shad and really ragged looking then I know there's been something messing with them in the last few minutes ... most of the time it's bluecat or striper or something like that that's storming through the shad keeping them from schooling up like they'd normally be if something wasn't messing with them ... now I know this wouldn't help you much if you were bass fishing but this is to just give you an idea of how to use your fish finder ... most of the time bass aren't going to be located right under your boat as they'll be hanging out around brush and stuff and towards the shore so a fish finder doesnt' help too much with that unless you get right up close to shore and figure out where there's good structure prior to fishing that spot ... for instance if the shoreline drops off kind of fast into deeper water ... like 10 ft or so or less and you go over that area with your boat to locate the good structure with your fish finder the fish will spook if you're that close to them so using the fish finder to locate the structure days before you're going to fish is a handy bit of knowledge to have the next time you go out because that structure like limbs and stuff that's fallen into the water around the shore isn't going to move and you can just get a lay of the land so to speak of where the good structure is and the next time you go out you know where everything is and you can fish that structure without having to get too close to it.

now using the fish finder for locating schooling fish and fish on sunken structure like crappie is a good use of a fish finder ... schooling fish like white bass, hybrids or striper you can use your fish finder along with the trolling motor to move around out on the lake's humps and what not to see where the fish are holding and drop down live shad to the fish on a downline and that's where a fish finder really shines and is the most help .... using your main motor to locate fish like that don't work too well because the noise will push the fish out from under the boat before your transducer ever goes over them too ... especially in more shallow waters ... the motor noise under water is very loud so the fish are going to move out of the way of the boat long before you go over them in say 10 ft or less water ... they don't move out of the way so much if it's really deep water though so that could be your problem if you're using your big motor and trying to locate fish cause they'll move out of the way. the only way to get a truer reading of what's down there is to be in stealth mode and using the trolling motor or drifting over an area where the exhaust of the big motor isn't a factor.



This page will take you through some stuff that is not really out there to help folks with GPS information. Information that's not readily available without hands-on experience. I'm just going to cover information about the Lowrance I-Finder Hand Held units and Lowrance fish finders with GPS capability. This really won't take that long to show you a lot of stuff that you just can't read on the Lowrance site and understand. It's probably there but it's confusing, so let's take away some of the confusion now.

First off, when you order your new I-Finder the H20 is probably the best one to get. It's water proof and a good all around unit. Things that don't come with it is the ability to load the downloadable maps off the Lowrance web site. In order to do that you have to have a SD/MMC reader/writer. You can get these with MapCreate package but you can also just buy the reader/writer from RadioShack for $9.00 or so if you don't want to spend a lot of money on map software that you may never use. MapCreate maps are handy though as I've got some for my area loaded on my SD chip and they show ponds and old lease roads that don't come with the Unit. All the old back-roads are on MapCreate and a lot of other things as well. So it's a good thing to have if you have the money to purchase MapCreate.

The maps that are in the unit when it comes from the factory are pretty plain but they show major highways and what not and the lake maps aren't very detailed but if all you want is a unit to show WayPoints that you mark on it so you can return to them at another time. Like if you find some structure out in the middle of the lake you can mark the Waypoint on your GPS and return to that exact spot. This is also handy for trotliners. If you set a trotline you can mark the spot where it is on your GPS and return to that spot with pinpoint accuracy and you don't have to have a marker jug tied to the line. You can use a drag made of lead to drag for your line instead of having a jug tied to it that anyone can see and check your lines for you. But, back to the GPS information. If you just want to mark WayPoints and save them on your GPS and you don't care too much about detailed lake maps like the Enhanced maps you can download at then all you need is an SD chip which doesn't come with the unit. You can purchase a 512 meg SD chip from Wal-Mart for about $14. They're located in the Phone/Camera section in the Electronics Department. That's all you need extra for just marking WayPoints. Now this information may be a little off as you may not need the SD chip but I think you do in order to save WayPoints and other input information.

When you get your Unit they'll probably already have upgrades for it when you get it. I purchased a new Lowrance 334c iGPS and there was a software update for it on their site before I even purchased the unit. I went to RadioShack and purchased the SD/MMC card reader/writer and a new $14 chip from walmart and loaded the software update on it and put the card in my 334 iGPS and it automatically upgrades all by itself when you put the chip in the unit and turn it on. Lowrance product updates are at so in order to use these updates you need the $8 reader/writer from RadioShack. The kind I got was the SD/MMC card reader/writer. They're $29, I paid $20 for mine but it was a different kind that they don't have in stock any longer. It plugs into your USB port on your computer and if you're running WindowsXP you don't need any drivers or anything because XP will automatically see it when you plug it into your USB port and map it as a Drive Letter on your computer, like it's another hard drive or CDRom and all you do is copy the files onto that drive letter when you download them from Lowrance. Simple HuH?! Well it is when someone explains it to ya like I'm doing here.

You can actually get 1 and 2 gig SD chips but they're not necessary ... the 8 or 16 meg chips that Lowrance sells for $50 or however much they are will hold a lot of maps so a 512 meg chip will hold as many maps as you could ever use on your GPS. Now where the big 1 and 2 gig chips may come in handy is where you're going to log your fishfinder output and then read them with Lowrance's Sonar Log Viewer . The handy thing about having the 1 or 2 gig SD cards is you'll be able to log a lot longer than you can on the smaller chips ... I think I can log 5 to 8 hours on my 512 meg chip so if you want to log more hours than that you'll need to spend about $40 on one of the 2 gig chips.

I was at Wal-Mart the other day and the 512 meg chips were $14.97. Lowrance units can't read a chip that's bigger than 540 meg so the 512 meg chip is as big as you can use.

Here's a little info on how to read a color lowrance fish finder and what stuff means ... in the top photo you'll see I've got arrows marked as A, B, & C. and I'll explain what each of those represent and try to translate what you're seeing when you see that stuff on your fish finder.

in the top photo the arrow marked A that's just under the depth reading of 25.0 is sending back mostly yellow and it's about 6 to 8 ft thick ... this is similar to what a catfish will look like but this is a ball of baitfish ... I'd guess the boat is moving about 2 to 3 miles per hour as it's showing good arches of the fish below on the arrows that are marked C ... those red arches are scaley fish and if I were going to guess I'd say they were striped bass/white bass hybrids or they could be white bass or striper too but if they were striper I'd guess the boat would have to have been moving about 4 to 5 mph cause those are pretty big arches ... if this boat were moving at 6 to 7 mph the arches would be quite a bit smaller but my guess is the boat is at 2mph or slower and these are hybrids ... the arrow marked B is a tree or some kind of standing structure of some sort. the arrows marked C at bottom are pointing to red with a little blue in them arches and this is returning the red because it's harder than the soft mud bottom as you can see the bottom is returning mostly yellow for a few feet then it starts to turn red down a few feet because of the denser signal being sent back and if it showed even further down past the red it'd be blue in the really hard packed bottom or rock ... rock bottom will return blue and red mostly and this soft mud is also why catfish send back a more yellow signature ... like that ball of baitfish ... the reason I say that's baitfish is because it's so thick and sending back a more soft signature but the blue around the edge kinda makes me think it's not baitfish as the baitfish should show little bitty arches in there ... it may in fact be showing that but it's hard to tell on this blown up picture.
The way I'd find out for sure what kind of fish these were is I'd drop about 4 downlines, carolina rigged or with a splitshot near bottom and see what happened ... most likely if you did that they'd probably not even get set in the rod holder before something took off with it with this many scaley's in the area. when hybrid fishing this is exactly what you want to see and then if they're feeding, it's hammer time.

on this second photo it's showing a ball of fish on the arrow marked A but again depeding on the boat speed it's hard to tell if that isn't just a bunch of sandbass ... if the boat was moving at 6 mph I'd say it was whitebass ... if it's moving slowly ... like 1 or 2 mph then I'd say all the fish on this screen was baitfish ... even the little arches ... those would be large shad if the boat was moving at a super slow speed ... 5 and 6inch shad will show up like the arches that b is pointing to and the big ball where A is pointing would also be shad or some kind of schooling baitfish at 1 to 2 mph ... now if the boat were moving pretty fast then I'd say these were white bass and possibly the ball was shad but most likely white bass also ... it's hard to tell without the information on how fast the boat is moving. the depth is also important when reading this because if it were 8 to 10 ft deep then you'd know these were shad for sure because in shallower depths the fish arches will be quite a bit bigger than if they were down deep at 25 ft. Also if these are shad then this isn't all that great of a spot to stop and fish because nothing is harassing them ... they're swimming in tight formation for the most part and if there were fish after them they'd be all busted up and scattered and that's what you want to look for ... busted up shad.



That's about all there is to it. If you have any questions be sure to ask them on the forum or you can email me at