Surprise surprise

[Douglas]

Couldn't get the attachment to stick

[Didley]

Interesting graph that one Doug, Thanks for that. I do wounder how anyone can put a figure on how many fish have gone over the wall. They have no idea.

[gunna]

I stood at Awoonga back then and watched them go over. You could clearly see the big girls but that was all. No chance of seeing anything smaller. I was also lucky to fish the bottom of the dam wall after the event. Looking down from the top of the dam into the area we fished, it looked like many thousands were trapped there. And that was well after the overflow. So while I won't dispute the figures, I do wonder how they counted ? Or what they used as their approximation.

[Douglas]

Both fair questions and comment.

I think that attempting to count (sampling or otherwise) is fundamentally flawed.

There is another way which relies on actual data.

A couple of the comments over the last couple of days (not the extreme claims, opinions or straight forward guesses) got me thinking so I had a further look and found something that I think is a lot closer.

I've got to convert it into graphical form so it'll take a couple of hours. It'll also put some perspective on a couple of things.

[Douglas]

Here's the first info on determining how many escaped from Awoonga in 2011.

3 graphs.

The first is the annual commercial take of barramundi from 2006 to 2015.

The 5 years 2006 to 2010 returned annual averages (lead-up to the 2011 overflow) :

. barramundi............. 9.6 tonnes

. fishing effort........... 165 days

. No of licences in use..14.


There were 3 overflow events.....2011, 2013 and 2015.

The first of the overflows had a dramatic effect and that's what we're trying to throw some clarity on.

There were escapes in 2013 and 2015 of lesser numbers.

The commercial netters put in a big effort in 2011 with a lesser efforts in 2013 and 2015.

The catches dropped from a high in 2011 of 248 tonnes, to 45 tonnes in 2013 to 30 tonnes in 2015. The years without overflows after 2011 still showed elevated catch levels as lingering result of the main escape in 2011. Escapes still took place in 2013 and 2015.

Just take a minute to digest the attached info.

Attachment 34255

[Douglas]

The important figurehere is the commercial take.

Total 2011 catch…………………………..248.3 tonnes

Average of 5 yearleadup to 2011……..9.6 tonnes

Therefore extra catch(248.3 – 9.6) tonnes……..238.7 tonnes

Number of barramunditagged in upstream Boyne River………168.

Number tagged thatmade it out of Boyne to other places………..72.(43%).

Number tagged thatdidn’t make it out…………………………………….. 96 (57%).

With a sample size of168 we can extrapolate that to the barra that came over the wall, the weight netted(238.7 tonnes) constitutes 57% of those that came over.

Therefore, weight thatcame over ………….. 418.8 tonnes
Weight that gotout………………………………170.5 tonnes
Weight that headedsouth……………………….14 tonnes

Hervey Bay’s averagetake before 2011……5 tonnes
2011 take …………………………………………………10.1 tonnes
Extra catch in 2011 ……………………………………5 tonnes
Although an extra 5 tonnes were netted, the more "barra friendly" estuaries in Sandy Straits and the Mary river provided better sanctuary than the Burnett which was netted out quickly. Even in between 2011 and 2017, commercial barra take in Hervey Bay has increased each year. I believethat's because its being drip-fed by the original 2011 escapees that found perfect sanctuary. I reckon that Al49 came across one of them.


Bundaberg’s averagetake before 2011………5 tonnes
2011 take……………………………………………………21 tonnes
Extra take in 2011……………………………………….16 tonnes

The hard data ends atthis point.

To convert to actualnumbers of fish divide the total weight by what you estimate the weight of theaverage fish to be.

If the barra averaged5 kg each=83,600( 44,300 netted) went over the wall

If barra averaged7.5 kg each=55,840(32,000 netted) went over the wall

If the barra averaged10 kg each=41,880.(24,000 netted) went over the wall

What GAWB didn’t havewhen they made their early estimate was the data that related to the taggingthat went on and nor did they have any idea of the commercial take until 2012.

We’ve got that dataand all we need to do is settle on an average weight.

But by any measure,the number is considerably more than they told me and more than what they toldFishing Monthly.

[BR65]

Nice to see an interesting conversation on Barra. We don't all agree on everything, and this thread has diversified, which isn't a bad thing I believe, they certainly stir people's passions. The cynic in me can't help but wonder if the number of fish that were lost was under reported in order to protect local stake holders interests.

[Douglas]

A couple of the comments certainly triggered me into having a closer look at something I thought had been done and dusted.

Sometimes, to get to a logical result, we have to go through a "dry" process which isn't everybody's cup of tea. People remember the outcome long after the process has been forgotten.

I also believe that stakeholder interests have been served but believe that it was an outcome rather than an intention.

I have a little more info to put up but its not about Awoonga itself. It's simply to give a bit of perspective on the subject of Qld barramundi.

[Douglas]

Here's the extra bit.

You'll see the spike caused by the Awoonga escapees and you'll see that it was Attachment 34264quite a significant event in terms of barramundi movement and commercial catches in Qld.

You'll also see a trend Qld wide but more significantly in the Gulf and NQ regions. Those regions were obviously not affected at all by Awoonga but coincided with good times in the Gulf.

But what's been happening since?

Shades of the current scallop emergency and closure of their replenishment areas.

Fisheries asleep at the wheel again?

Attachment 34264

[ActiveAngler]

Well no metre Barra from Lenthalls. Though the water level is dropping dramatically.