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Jedi Seadog
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Post Posted: Fri Feb 01, 2019 9:11 am    Post subject: NT project

Am looking a bit more specifically at water characteristics.

Need some remote assistance to do that from down here in Rocky.

I want to look at the real/actual effect underwater of visibility in varying degrees of "murkiness" (turbidity). I've done a lot on the research side of things already but want refine that practically.

To do that I'm looking for somebody who gets around in rivers/creeks of varying water quality that the average person fishes in. More than one if others interested. Can easily be done when on any fishing trip.

Need to have a Secchi Disc (I'm sure everybody has one :bs: in their boat) and a Go-Pro (or any underwater camera) on a stick.

Idea is to measure the turbidity with the Secchi Disc and then lower a Gro-Pro down into the water to see what the underwater view is at that depth. Much more practical and realistic.

Making a Secchi Disc is as easy as p..s. Show interested party how to do it. A metal disc about 150mm (6 inch) diam painted on upper side in black and white quadrants and lower horizontally into water by a string/thin rope with measuring marks on it. Note the string depth when the disc disappears. That's all there is to it.

Learn a bit more about barra fishing as we go. More than happy to share results and acknowledge assistance.

Volunteers on here or by PM if you want to take part, please.

Last time FFF did a project we ended up with the Darwin Ch21 VHF marine repeater with 2Rods doing an enormous amount of work at the Darwin end.

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Jedi Seadog
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Post Posted: Sat Feb 02, 2019 9:20 am    Post subject: Re: NT project

Thanks for taking time to look at the post.

In Matt's articles we've looked at all sorts of stuff that impacts on what goes on out of sight (underwater) when lure fishing.

The one thing we haven't done yet is look at CONTRAST meaning how well does the lure stand out against its water column background. Contrast also between colours on the lure itself AND those against the background.

To begin to shed some light on that (pun intended), this is what we want to do. Be able to copy what this guy is doing.

http://diamond-less.blogspot.com/2013/0 ... idity.html

What a Secchi disc looks like (6 inch - 150mm diam). Simple to make.

I use a turbidity tube (look it up).

I keep saying - " It ain't rocket science" and it really ain't.

This exercise is to look at the background colour against which your lure is going to be swimming. CONTRAST.

The bottom line is no contrast then no see lure.

The other limiting factor is visibility (how far down the light penetrates) and that depends on turbidity (murkiness).

No light then no see (again).

The Secchi disc gives us light penetration and the camera gives us background colour. What more assistance could we ask for?

Happy if a volunteer doesn't want to give location away, then that's fine. It wont be revealed.

Interestingly the guy in the video knows that the water beside that jetty is 7 ft ( nearly 2m deep). The Secchi disc string depth of 6 decimetres translates to a water clarity of 8 NTUs. A decimeter is just a fancy way of saying 10cm. 6 decimetres = 60 cm. Don't know why these guys want to make simple things seem complicated. He's swapping between scientific jargon of decimetres to feet so much that he gets himself confused by saying " a foot and a half". Its not. 6o centimetres (6 decimetres) is 2 feet.

He's in Chesapeake Bay (Maryland in US) and 60 cm ( 8 NTUs) is pretty clear water that we'd kill for here in the Fitzroy. In some NT rivers too.

Yet look at the camera image when on the bottom. Really murky although I'd say that camera hitting bottom stirred up some muck. But look at the image clarity when on the way down. Looks rats..t.

However the important thing to note is the background colour of the water column as the camera goes down. There's no distance marker out from the camera to visually give some sideways distance perspective but that's easy to show.

There is the project.


Taker/s?


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Jedi Seadog
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Post Posted: Sun Feb 10, 2019 9:46 pm    Post subject: Re: NT project

OK. Nobody wants to play with turbidity discs. Fair enough.

Are there any takers then for taking some underwater pix for differing colours of water that you guys can expect to fish in?

Just put the camera down about a metre or so and take a pix looking away from the boat (or bank) would be fine. No flash, eh!

Any takers for that little job?

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Post Posted: Mon Feb 11, 2019 9:08 am    Post subject: Re: NT project

Given that this activity might interrupt beer drinking you might not get too many volunteers. Can it be done while holding a stubby?

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Post Posted: Mon Feb 11, 2019 2:28 pm    Post subject: Re: NT project

Sounds good but I've got no camera


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Post Posted: Mon Feb 11, 2019 5:33 pm    Post subject: Re: NT project

I've been scratching my head with this for a while.

I've got a water proof >10m camera but I can't work out how I can push the capture button let alone point it the right way and no matter how much beer I feed the deckie, he's still not going to trust me if I hold him by the ankles over the side of the boat. :D

I'll keep thinking though.

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Post Posted: Mon Feb 11, 2019 6:30 pm    Post subject: Re: NT project

NinjaFish wrote:
I've been scratching my head with this for a while.

I've got a water proof >10m camera but I can't work out how I can push the capture button let alone point it the right way and no matter how much beer I feed the deckie, he's still not going to trust me if I hold him by the ankles over the side of the boat. :D

I'll keep thinking though.


1. Use the selftimer set on 10 sec. ..... or
2. record a video then screenshot off it is what I will be doing.

Any chance of sharing out the 250 bucks that this article will be worth though ronje ??? 3 pics should be getting you about $90 or more according to the rates Matt has for articles with $250 being the maximum payment no matter how many pics are included with the story....a bit of fuel and couple of drinks would be a decent incentive and get more research into this mystery done.


Pics of cleanish freshwater in the upper howard river ....<1m from disc

my sachi disc actually has a guns and roses 110mm squidgie below it too. I was really surprised at the lack of visibility in water on the cleaner end of the scale as to what we usually fish in this river.


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Jedi Seadog
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Post Posted: Mon Feb 11, 2019 8:39 pm    Post subject: Re: NT project

Thanks, Flick'n.

Where on earth did you get a Secchi disc? Full of surprises aren't you.

Do you know how far it had to be lowered until it disappeared from view looking from the surface down into the water? I can calculate the turbidity from that.

Anyway, the turbidity isn't high but enough to affect the G&R lure under the disc. Remember that the G&R lure is in the "shadow" of the disc and the amount of sunlight is being blocked significantly so it's not a good test for the G&R lure. If it was out of the shadow of the disc it'd probably be a lot better.

Anyway, which part of the G&R lure can you see? The green colour or the red colour? Does either of them stack up against the white of the Secchi disc? Remember what I said about white lures? Remember what the US Navy dive centre said about white colours? I'll ask that question again when we get some pix with different coloured water and rurbidity.

Anyway, we've got the background colour of the water to provide contrast.

To give the max chance of the a lure being seen by a fish against that background "wall" is what we're looking for. Obviously white (like part of the Secchi disc) contrasts with the background "wall" colour but black sure DOESN"T stand out on the mainly green background.

The light from the sun is travelling down through the water to the disc (60cm) where its reflected to the camera (80cm maybe?). 60cm + 80cm (to the camera) means that the light penetrates 1.4 m further than the camera at least and still hasn't faded out.

Remember the barra's party trick eyes which allows them to see further in dim or very low light? A barra can see the white of the Secchi disc for another 1.4 metres. The black colour a lot less so. So a barra could see light down to 2.8m in that water. If yr lure was a 3 m diver then all it needs is to contrast with the background to be more visible.

Based simply on colour alone, how do you reckon a green lure would work? Or a red one? Or a blue one? Some other colour variation?

Now are we starting to think about things a little differently?

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Post Posted: Mon Feb 11, 2019 10:23 pm    Post subject: Re: NT project

ronje wrote:
Thanks, Flick'n.

Where on earth did you get a Secchi disc?

Do you know how far it had to be lowered until it disappeared from view looking from the surface down into the water? I can calculate the turbidity from that.

Anyway, the turbidity isn't high but enough to affect the G&R lure under the disc. Remember that the G&R lure is in the "shadow" of the disc and the amount of sunlight is being blocked significantly so it's not a good test for the G&R lure. If it was out of the shadow of the disc it'd probably be a lot better.

Anyway, which part of the G&R lure can you see? The green colour or the red colour? Does either of them stack up against the white of the Secchi disc? Remember what I said about white lures?

Anyway, we've got the background colour of the water to provide contrast.


I actually made the disc myself this arvo with a yoghurt lid and a pair of scissors and a texta then installed a roofing screw to sink it I nearly lost it in a snag too mate.

It was hard to see from the suface in the evening sunlight even in only 60cm

The fluro red is a decent contrast to the background water colour and far more visible than the fluoro yellow or green with black stripes.

The guns n roses lure is 110mm so by my reckoning at least half of it is still in the sun which was already below the treeline as mentioned (with the disc having only a 50mm radius ) and if you take a closer look at the bottom pic it is actually sitting to the right out of its shadow near the disc on the bottom of the river behind it. Perhaps I might change it to a drop bear coloured one for the next test though to see how that goes.

Often we are casting into the shade of steep banks and inside the culverts themselves or underneath big snags ..... so i think the test is still a realistic one for that lure.


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Post Posted: Tue Feb 12, 2019 1:48 am    Post subject: Re: NT project

Nice work flicken..


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Jedi Seadog
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Post Posted: Tue Feb 12, 2019 7:01 am    Post subject: Re: NT project

Well how about that. A yoghurt lid. Innovation as its best. Good on ya. And a valid point about shade. More shade means less light. Less light simulates higher turbidity.

The setting sun in your pix means the light is coming in at an acute angle and a lot of it is being reflected away by the water surface and not penetrating. There's a lesson in that for later.

I could see the lure on the bottom and the red head stood out marginally better than the green body (realistically both were rats..t.)

But neither compared well with the white.

You see, a really good test for contrast is to run a couple of similar sized lures (and differing colours) past the recording camera against differing backgrounds. Then (as you said), pick off screenshot images as pix.

I've bought a little cheap u/w camera. I already have a turbidity tube device (bit like your Secchi disc) so can easily do the tests while monitoring the turbidity as well. But that's in local water in CQ of varying turbidity and colour.

I've already done the subject of light penetration in water.

What I wanted to do was include you guys in the article research so you'd understand a bit more about the importance of water colour and turbidity effects and how the two combine with contrast to produce an outcome.

At the end of the exercise, there's a bit of a surprise about how the two combine.

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Post Posted: Tue Feb 12, 2019 9:46 am    Post subject: Re: NT project

That's some interesting reading Flicken and ronje :mrgreen:

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