Project assistance

And jacks, salmon, jewfish - tell us how you went. NT, FNQ and Norwest.
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ronje
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Project assistance

Post by ronje » Wed Oct 16, 2019 6:18 am

Hello

Thinking technically outside of box again.

Looking for help with a little research project. Need assistance with barramundi measurements. Am looking at size of barramundi mouth compared to overall length.

Asking that anybody who decides to keep a barra, measures 2 dimensions and sends them to me, please.

. length; and

. diam of stretched open mouth.

See example attached. Its an jumping 80cm barra that I was lucky to photograph 1 handed a few years ago.

Look at mouth. Almost perfect circle.

Want to use those measurements as part of a project which I'm happy to share results of on FFF for all.
80cm jump Frogmore June 2002.jpg
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Ronje

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Re: Project assistance

Post by ronje » Thu Oct 24, 2019 7:23 pm

Must be a pretty lean time up there.

Measured a 70cm barra today @ 70mm dia mouth.

We've all heard the stories about bucket-mouth and implosions and enormous amount of water flying. All very dramatic descriptions.

Anybody want to hazard a guess about how much water is involved in a strike by a 70cm barra?

Also measured a 1 m king thready at 90mm. Guesses on amount of water for a 1m king threadie?
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Ronje

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Re: Project assistance

Post by Matt Flynn » Thu Oct 24, 2019 8:10 pm

It is quiet Ron, even on Facebook. And look at the MDF score so far ... https://www.milliondollarfish.com.au/

No tagged barra yet? Slowest year yet for MDF returns?

Seems to be more sailfish than barra reports.

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Re: Project assistance

Post by ronje » Fri Oct 25, 2019 5:03 am

Gathered that, Matt.

I can get by for measurements of frames in freezers from down here although bigger fish ( 1m+) tend to be released.

Wanted to give FFF'ers the opportunity to do something different, think about barramundi fishing in a more technical sense and dispel a couple of myths along the way.

A hard fishing environment tends to make one think a bit more.

U know, those MDF had to be caught and tagged a few weeks ago under the same conditions as are currently in place up there. 105 fish in 10 days or so (sorry...126 fish). It wasn't as easy as previous years but the guy did it.
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Ronje

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Re: Project assistance

Post by ronje » Sat Oct 26, 2019 6:07 am

Barramundi are what's called "suction feeders".

They manipulate the shape of their mouth cavity, shut their mouths tight, push water out via the gill covers which then close creating a sealed container (their mouth and throat)which has a lower pressure than that of the surrounding water.

They then open the other end of the cavity (the mouth) allowing the surrounding water to flow in to equalise the pressure.

They thrust their lower jaw forward, open their mouths wide thus allowing the water immediately in the front of their wide open mouths to flow towards (and into) the open cavity. Higher pressure volumes will try to fill the void of low pressure areas so the flow is into the mouth.

Naturally anything in the water immediately in front of the mouth flows into the mouth as well. eg a fish, prawn or a lure.

As the mouth cavity (there's a proper name of "buccal cavity") has a volume of 500ml then only 500ml can flow in. What the barra wanted to eat has to be contained in the 500ml immediately in front of the mouth and the "suction" is reducing rapidly the further out that we look. Not much is it.

So, what is the volume of a barra's mouth cavity in which all of this happens?

That 70cm barra I asked you about has a maximum volume of...…… 500mls (half a litre). The mouth cavity is basically a cylinder of 7cm base and a depth of 13cm.

The 1m king works out to almost 1 litre (.9). 9.5cm base x 13 cm depth. A big difference although 1m barra needs to be measured to compare apples with apples.

All the action in suction feeding takes place in 20 milliseconds ( 1/50 th of a second) so the barra had better get its suction mechanisms working with perfect timing to get a feed. Shut this, open that, force water out, seal that, open this, shut this, open that again(to filter water out via the gill openings).

Pretty simple? The theory is but not everything always goes according to plan, does it.

I'm looking at the next step in the process of understanding the tools that a barramundi has to survive and how knowledge of those tools can help us increase our chances of catching the bl..dy things.

We now understand (or should) how their lateral lines operate, their eyesight, how light and colour combine in a barramundi's world.

I'm now looking at how (now that we've attracted a barramundi's attention by using the understanding we're gained so far) we can use knowledge of their feeding mechanism to our advantage.

Knowing these things now, think about what we might be able to do with our lure to help the barra get it into its mouth. THAT'S where my thinking is headed.
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Ronje

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Re: Project assistance

Post by ronje » Sat Nov 09, 2019 7:18 am

From the Fitzroy, I have a measurement of 104mm at full gape for a 84cm barra measurement of 104mm.

So that's 2 sizes accounted for. Extra 14cm of length resulted in increase of gape of 34mm.

4 mates (more than I thought I had) gone to Peter Faust dam claiming to be on a research trip to get some more measurements. There is an up-side to boring old research sometimes.
Regards
Ronje

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