Barramundi trends

And jacks, salmon, jewfish - tell us how you went. NT, FNQ and Norwest.
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Matt Flynn
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Barramundi trends

Post by Matt Flynn » Sun Sep 02, 2018 5:00 pm

Further to discussion in the poll about the lack of 120cm+ barramundi out of Shady Camp (but there's quite a few 90cm and metre fish), here's a graphic showing barramundi catch trends in recent years, from the federal fish website and the 2014 NT Fisheries report. It is Australian and NT barra catch.

Keep in mind they go up to 2015 and recruitment is now trending up on the back of two recent Wets.

I've also put Darwin annual rainfall since 1980 as a rough rain guide.

Point Stuart rain is more applicable to Shady but less complete, here ... http://www.bom.gov.au/jsp/ncc/cdio/weat ... num=014263

Interesting that the 1980s don't look anything special re Wets, keeping in mind 120cm fish will be 10+ years old, and there were heaps of 120cm to 130cm fish out of Shady in the late 1990s.

Maybe the Wets were special locally?

Keen to hear thoughts.

Note the Gulf of Carpentaria catch trend, way down, has been same with mud crabs (not shown).
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Re: Barramundi trends

Post by ronje » Wed Sep 05, 2018 1:58 am

Matt

Look at 2011 year. The bright green segment (central east coast). That was the wet year that saw a huge escape by big barra from Awoonga Dam (Gladstone) when water went 4m over the spillway.

248 tonnes of barra were netted at the mouth of that river (Boyne R) nstead of the usual 8 - 10 tonnes.

Just that 1 single event skewed the national catch.

Lot more fishing effort these days than in the 80s during the spawning events at the mouths of those NT rivers?

Spawning events take place at low water at those river mouths when salinity/temperature and tides align. Then timing of the run-off determines the success (or otherwise) of subsequent recruitment up onto the flood plains.

Do you know where the figures for the rec sector came from and how reliable they might be? I can understand logbooks for commercial/ guided activity may give data but rec sector figures?
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Re: Barramundi trends

Post by Matt Flynn » Wed Sep 05, 2018 7:23 am

Interesting. Not sure Ron about where NT rec figures come from, they do have FTO log books. They have less commercial catch data since the NT net closures.

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Re: Barramundi trends

Post by stroma » Sun Sep 09, 2018 10:09 pm

Just a thought
An ecosystem has a limited carrying capacity irrespective of the species of fish or the size class. When the commercials netted the area they predominantly used 6 inch mesh to target smaller fish that the market prefers. In doing so they removed a large proportion of the smaller size classes of fish and generally avoided catching the big girls. In the absence of this netting activity has the population returned to a normal balance of lots of smaller fish and fewer numbers of large ones?

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Re: Barramundi trends

Post by fish4me123 » Mon Sep 10, 2018 8:49 am

gee so much unknown. Why would there be less big girls?
tight lines

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Re: Barramundi trends

Post by NinjaFish » Mon Sep 10, 2018 3:03 pm

Body image shaming from social media platforms? :rofl:

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Re: Barramundi trends

Post by ronje » Mon Sep 10, 2018 7:15 pm

they predominantly used 6 inch mesh to target smaller fish. In doing so they removed a large proportion of the smaller size classes of fish and generally avoided catching the big girls

Dont know about that Stroma.

A 6 inch gill net doesn't avoid catching big fish at all. It simply lets small ones slip through or force their way through.

A big barra will surge forward upon feeling resistance and force its head partly through with the mesh slipping over the gills and the fish is head caught. Cant pull its head back or go into reverse.

I dont think anybody really knows until some records start to be kept.

Saw some magic here in Rocky the other day that basically does away with the tagging system for data accumulation.

Local has bought a side-scan Biosonics sounder from the US and taught it to recognize fish shapes by modifying facial recognition technology used by security services and law enforcement agencies world-wide...

Biosonics scientific sounders start at about $100,000 US.

It can distinguish between barra and king for example and can also count them as well as give size.

So sounder can be told to reject data of barra and/or threadfin below a certain size or above a certain size.

I saw a section of river ( a couple of km long and both sides) that displayed on a map every fish that fell within the parameters set by the operator.

That section of river showed 11,000 barra and king (each with an i/d number) that the sounder saw along with the GPS point at which it was seen.

Translated onto GE map.

Was purchased for business purposes for measuring aquatic biomass and doing things like showing the actual numbers and types of fish in a system, dam or anywhere else.

Imagine this thing being run past the mouths of the Mary/Alligator systems at spawning. It'd give you a map of every barra, gps, size etc of all barra taking part in that process.

It'll also recognize, count and GPS mark crocs or anything else that you want to teach it to look for. Run it up the Adelaide and it'll count the number of crocs and show where they are by GPS if you want.

I've never seen anything like it.

Here it is

https://www.biosonicsinc.com/products/dt-x-extreme/

Can look sideways and has low frequencies therefore range sideways isn't a problem. Can do that down to 37 khz or up to 1000 khz. Just pick which transducer to suit.

It also has manual control of pulse duration so can produce range resolution figures better than any auto CHIRP found on any of the modern expensive models.
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Ronje

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Re: Barramundi trends

Post by NinjaFish » Fri Sep 14, 2018 10:13 am

That is impressive, almost like the first Mission Impossible movie where one could only shake their head at the technology. So now fish can't even hide from facial recognition! I would love to see it in real life action one day but in the mean time I'll keep learning to operate my now apparent outdated Lowrance units.


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Re: Barramundi trends

Post by mafoo25 » Fri Sep 14, 2018 4:58 pm

No more Netfilx!

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Re: Barramundi trends

Post by ronje » Sat Sep 15, 2018 5:38 am

Nearly at that stage now, Matt.

It gives all of the data at one point in time. Change of tide means that fish change.

Obviously use is for research purposes but it gives clues about what direction recreation sector sounders will proably head.

Basically put more scientific emphasis in rec fishing. Enhance the role of citizen science in the activity.

Most of the auto CHIRP sounders available these days are "throttled back" anyway to allow for user "churn" (market needs users to continually upgrade to more advanced models). Drip-feeding technological change ensures churn just like mob phone industry does. Exactly the same principle.

Will put up some examples of results when Bill releases them publicly.
Regards
Ronje

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