Threadfin salmon, local populations

[nadders]

Hi Guys,

I was sent a copy of the finalised report on threadfin stocks in Australia, thought I would share for anyone interested.

The study was undertaken by JCU and can be found here:

/>http://www.ffc.org.au/FFC_files/Welch_et_al_2010_final_report_threadfin_stock_structure_Sept_2010-1.pdf

here is what i understand about the findings:

In terms of local populations, the research suggests that the fish are very sedentary and little mixing of populations occurs. mitochondrial DNA sampling also suggests that the Brisbane river population are in fact indigenous to the area and didn't come to be through migration from up north etc. i've held that opinion for a long time but it's good to finally have the report out with some more meaningful figures

one of the recommendations made was that fisheries management should be done on a population basis instead of state-wide, as the mDNA sampling suggests that not only is the Brisbane population different from the others up the east coast, but that each individual population is distinct so the abundance of fish in one system has little relevance to the abundance of fish in another in fisheries management terms

for the relevant info i suggest you start reading at page 109, but the whole thing is a great read if you can put up with the science

cheers

Dan

[eg_vtec]

thanks for sharing dan. good stuff to read

cheers

[rayke1938]

Thanks Dan now all that is needed an effective management program such as seasonal and bag limits such as one in posession say including and south of Noosa River.

They do the same with other species and seeing that they are not a significant commercial catch in our waters there really should not be much opposition from the commercial industry.

just have to give the minister a kick in the butt to get him motivated.

Cheers

Ray

[nadders]

i am told that fisheries are discussing things like a max size as are in place in other protandrous hermaphrodites (barra, flathead), which is what I've advocated for a while but who's to know if it will actually occur as I have read discussions from years ago about the same topic up north.

but hopefully the advice will be taken on board regarding the stock separation, the current paper tested a lot of different things including growth rates and the stage at which the fish were changing sex, and the findings were often wildly different between different regions, so it really makes no sense having state-wide management plans in place of a species whose populations can have a different life cycle as little as 50km or less apart.

i am glad theres something more concrete anyway to place the salmon in the river as indigenous instead of a magically invading symptom of global warming, i've been waiting for the evidence for a while!

cheers

Dan

[Thirstyman]

yeah its cool to know they are orignally from here...

[rayke1938]

Just finished a more in depth scan but skipped blue section.

Very interesting but a lot of it over my head.

Looks like there are dominant females everywhereB)

Dan do you know if Brad is still collecting samples?

Cheers

Ray

[nadders]

the p109--> section is the one that relates to the brisbane river, which wasn't included in some of the other measures (they used a variety of different methods to support the localised population hypothesis on top of mDNA sampling).

there is lots of interesting stuff in there for example the lengths at which the fish mature and how it changed between regions. eg the fitzroy river samples started changing at very large size of 120cm, whereas the samples from some of the regions in the gulf of carpentaria were changing at something comparatively rediculous like 40cm

some real monsters in the fitzroy samples biggest being 1612mm

another interesting snippet was distance travelled, there were some tag recapture details included and of 235 recaptured fish only 4 travelled more than 300km (longest distance of 600km) and of the remaining 231 the average distance travelled was 16km

I would be surprised if he was still collecting frames Ray as the report is now published but Brad will have to confirm or deny that for himself as I don't know if he is involved in further projects

cheers

Dan

[tugger]

thanks dan for that info and a big thanks to brad for the study

[mick fillet]

very good reading cheers dan.

its great to see the report thanks to brad and all those fishos who contributed to the findings

[wesfish]

interesting reading! great stuff dan, i all ways said they were all ways here and did not just magically appear lol

[elops]

The thing I found most interesting and somewhat dissapointing was that after repeated calls for samples in various media and forums only 25 were collected from the Brisbane River. Would have seen pics of probably twice that number on this forum alone.

[ellicat]

50%'s not a bad strike rate though.

[rayke1938]

The thing I found most interesting and somewhat dissapointing was that after repeated calls for samples in various media and forums only 25 were collected from the Brisbane River. Would have seen pics of probably twice that number on this forum alone.

Maybe most of them were released.

He got the frames of everyone that I kept and I did bump his post a few times.

Cheers

Ray

[elops]

All 25 did not come from here ellicat.

I know you did Ray, not the only reasearch you have helped with either always willing to help when ever possible.

cheers

Steve

[ellicat]

Good point, Steve....sorry - a bit distracted by the less than helpful members

[tugger]

it was all to easy to help as brad would come to your place and pick up the frames i tried to meet him half way but he would not have a bar of it so i donated a couple of frames as i don't fish the brissy much and have only caught a couple of threadies over the last couple of years.

i know they have been around a while though as i found my first down the river nearly 8 yrs ago now before the word really got out, it was a floater that had either been hit by our boat or it was suffering from barratrauma from being caught prior to us finding it.

they do suffer from this trauma easily and we now find them regularly at work dead or dying along the banks of the river from well meaning fishos trying to release them.

[nadders]

ive found a few floating too mark it's a huge shame to see. especially given that with a little care, thought and the right equipment (release weight) they release quite easily

imo everyone that plans on targetting these fish should invest in a $10 release weight, huge shame to see big females flapping on the surface after 6 hours of floating