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fish finders...

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Well-Known Member
Sep 1, 2003
Hi guys,
We recently bought a new boat and it came with a Humminbird 400TX fishfinder :) Today, on the way home I opened it and saw some "big scaled" fish in the depths of blue. Well my question is to any of you with an experience in using these gadgets.
- How does it makes its scan? I mean does its send its beams longitudinally or horizantally? In other words the underwater topography that we are watching from the monitor is in which direction?

Thank you very much for your helps.

Here is the machine and the map pictures.

Hi Memo,

I use a fish-finder almost identicle to that Hummingbird in the picture on my kayak.
As I understand it , ultrasound waves are transmitted from the transducer downward from the surface and are reflected from the bottom (+/- fish) back up to the receiver. What you get on the screen is a real-time image that is dependent on the acoustic properties of the sea-floor (+fish that happen to be there). The actual size and rate of the field that is transduced at one time will probably depend on the sophistication of the transducer/receiver and the fish-finder itself.

The fish-finder in your link is quite basic but is more than adequate for spearing. Hope you get my drift!!!

Hi Mlungu,
How and where do you place your fish finder onto your kyak???
I thought most of the fish finders were just water resistant and not exactly waterproof if you happen to accidently flip your kyak.
it depends on the fishfinder. the basic principle is that it projects ultrasound waves from your transducer, and the waves bounce on the seabed and/or fish back into your reciever. fishfinders use the same basic priciple as does radar. depending on your fishfinder, you can also have it setup so that you get a split screen showing you what is directly below you and also at a certain distance in-front of you. also, consider that when going above a certain speed, your fishfinder will not display accurate readings.

good luck
Originally posted by LongFin
Hi Mlungu,
How and where do you place your fish finder onto your kyak???
I thought most of the fish finders were just water resistant and not exactly waterproof if you happen to accidently flip your kyak.

Here's a picture of my Kayak, Longfin.......

The console just sits on top held in place by an elastic cord. The unit is fairly waterproof and I have flipped my kayak with the finder on board with no ill-effects.Iam not sure about other brands.As you can see the transducer is stuck to the bottom from inside. The battery also stays inside. The only problem I have had is that the connectors have corroded slightly and need to scraped every now and then to get a good contact. This set-up seems fairly bomb-proof and I have had no problems.:)


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Mlungu thanx mate, I love using the fishfinder it resembled me an arcade pc game :D I also found the online catalog of 400tx from hummiinbird.com but there is still one unclear thing in my mind. I saw some small fish and also some big fish in the monitor, how big is the big fish symbols? do you have an idea?

Hey memo, post some pictures of the new boat!!!

Hiya Mlungu, now i'm confused :confused: Are you Mlungu or Induna ????? :D :D I reckon i'll stick to boss-man!!! :D :D
Greetings from a sunny but windy Cape Town :D :D

Hi Miles,

Yep, Mlungu and Induna.......a wit Nkosi would be over the top!:D We' ll have everyone talking Zulu on this forum soon!

I'm coming to SA in a couple of weeks for hols... staying with family on the Natal north coast so hoping to get a bit of spearfishing done. Really looking forward to it.Just hope the conditions are good. Every time I go the wind starts pumping and the fish are scarce :head Won't have my kayak though

Seems you guys in the Cape are hitting the yellowtail and the rest!



Nice!!! Should still be decent weather. Will be nice to shoot some decent fish again.......especially after all that cold weather you've been getting used to!!!!

Just PM'd you.


I can't really tell you exactly how the sizes on the screen correlate with actual fish size. Once you go over a reef with plenty of fish the thing starts bleeping like crazy with small and large fish on the screen and that's when you dive in!!!
O'right I'll be diving in that place tomorrow morning to see how big is that "big ones " ;)
first of all let me assure you there is no such thing as a "fish finder"...they are bottom sounders despite what the manufacture claims! We even have other charter boats claim they have "fish finding electronics" onboard.

The basic principle is a cone shaped beam(pointy end at the transducer) is bounced off the bottom of the sea and return information is shown on your screen. Anything midwater preventing the beam from reaching the bottom is shown midscreen, could be fish, debris, little space men is submersible suits, whatever. The accuracy of the unit depends more upon the tranducer strength and mounting style(through hull, rear, or in hull) With the unit on our boat(color) I can tell the difference between hard bottom and sand or mud, ect by the strength of the return. This takes a little time and fine tuning. Learn to use the zoom function and get the best transducer you can(dual frequency transducers are a god send!) Using the zoom on a good sounder will help you differentiate between a tightly packed bait ball and a larger predatory fish.

Good luck
Hiya Rigdvr

I wish to disagree with you :D :D (if thats ok with you :D )

Firstly, that little fish symbols you see on the screen is more a gimmick than anything else. Put your FISH ID. off on your echo. Fish will now be shown as either arches or little scratches on your echo. The entry level echo's are really only good for reading water depth and the bottom structure. Reefs and pinnacles will generally show up quite easily on most echo's. The entry level echo's are great because they come with no frills and are generally very user friendly. Play around with your settings to get the best out of your echo. In all honesty, for spearing all you want is water depth and bottom structure.

A bit of background. I spent 8 months owning my own commercial fishing boat. We fish with handlines and went to sea virtually everyday (weather permiting of course) Our target species were yellowtail, cob (mulloway/jewfish) and cape salmon. All these are fish that swim in schools. I started out with a monochrome furuno4000. Was a good echo but we battled to differenciate between baitfish and predatory fish. I eventually bought a Koden colour echo, at 3 times the price of the furuno. The difference was amazing!!! We could tell from the size and type of writing on the echo, what type of fish was below us. We really did well with that colour echo. On my tuna boat, i had a colour furuno echo. whilst trolling for YF tuna, you would ride over a school at say 10 fathoms deep, and then you'd see the red mark on the echo as the fish rise, seconds later the reel/reels would be screaming.

So to sum it up, as a spearo, an entry level echo is brilliant, but if you're really hardcore and really into shooting schooling fish, i'd suggest a top of the range colour echo from any reputable brand.

Just my .02c

miles:D :D :D
what did you disagree with me about??? You just said the same things I did...

I use the sounder for the same purposes as you both on the reef and offshore but I still wouldnt call it a fish"finder"...a fish finder should tell me where to go a I leave the dock, by the time the sounder spots fish, hell, Im already there:D

humblest apologies :D :D

Now i get it !!!!! FISH FINDER.....:D :D
I normally use my local tackle shop to find the fish for me !!!! We have a very funny tradition here in Cape Town. Out Tuna fisherman are very few because of it being such an expensive sport. A shimano tiagra 30lrs and matching rod would cost about R7500.00 (about US$1100.00). Now consider the fact that you need at least 4 trolling rods and four bait rods. Thats about US$9000.00 worth of tackle as your bare minimum. Our boats also have to go 30-40nm out to sea to catch those yf tuna. Our waters is called Cape of Storms..... Anyway, because of the huge sums of money laid out in tackle and fuel costs, there is a gentlemans agreement between tuna anglers to notify others when they're catching fish. So all you do is run out the morning and listen to your vhf radio. As soon as the guys start getting fish, they'll broadcast it on the radio, giving type of fish, size as well as latitiude and logitude positions (gps co-ordinates) Then you simply run to them and join in the fun!!! :D This is evenm done in competitions!!:D Hows that for a fish finder:D

wow! thats sweet!

does any biquering start over who cought the biggest fish and the usual sore losers??
thats how most of our charter fleet operates. Most of us participate b/c we know what its like to be on the outside of a good bite! I share info with the other guys so they will share with me kinda deal...not like it is in S. Florida.
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