Mangrove jack research in NSW

[Leaping bonito]

Hey Fishboy018,

Don't give up on the jack research mate, my project will really only scratch the surface, there's still plenty to be done on them. I've sent you a PM with one idea, see what you reckon and good luck with it all.

Cheers,

Toby

[Leaping bonito]

G'day Ausfishers

Well, I decided an update on the jack project is well overdue. The work is going well, with all of our tagged fish recovering very well from the tagging surgery.

Frames are also coming in nicely, so thank you very much to everyone who has donated. It would be really excellent to see them keep coming in, and every single frame will be put to good use.

We've also just had our first jack for tagging from the Clarence. The fish was caught by a rec fisho and kindly given to the project. For every live fish (up to the first twenty fish) from the Clarence and Deep Creek (south of Coffs), we are offering a $50.00 voucher for either tackle or fuel. All tagged fish are released back into their capture location.

Here are a few pics from a recent tagging session.

If you have any questions, please feel free to contact me.

IMGP0030.jpg
Here is a jack in the anaesthetic bath just prior to tagging surgery. The anaesthetic is administered to the fish in their water, rather than by injection.


IMGP0027.jpg
This is a completely anaesthetised jack awaiting surgery. During the surgery, the pipe in the picture is placed in the fishes' mouth. It runs water and anaesthetic over the gills. The whole surgery procedure only takes about 4 minutes.
IMGP0033.jpg
Getting ready to make the incision. The red/orange stuff on the fish is Betadine. Maintaining sterility is really difficult with fish, since they are covered with water and their own slime, both of which are obviously full of bacteria. Any attempts to scrub away at their skin with disinfectant also generally do more harm than good, by removing their protective slime and damaging their skin. However, a gentle swab with a cotton ball soaked in Betadine doesn't do any harm, and helps to reduce infections.
IMGP0032.jpg
A more distant shot of a jack in the surgery cradle. The fish is held between two pieces of wet foam, while a portable bilge pump circulates water and anaesthetic over the gills.

IMGP0038.jpg
Stitching the fish up once the tag is in.

[Leaping bonito]

Hi Ausfishers

With the jacks fairly quiet down this way (NSW mid-north coast) until next summer, I thought it was time to post a quick run-down of progress in my mangrove jack research project for the 2011/12 jack season.

My supervisors and I tagged 22 jacks with acoustic tags. The largest was 57.5 cm to the fork of the tail, and there were two others at 57 cm. The first receiver download is coming up in just over a month, so we should have some good movement data starting to come in.

Fishos (both spear and line) very kindly donated 70 jack frames. These are extremely valuable for my research, and I really appreciate every donated frame. These will be used to age the fish, to determine their size at maturity, and to study their stomach contents.

I'm definitely still after frames, so if anyone catches a jack anywhere in NSW and keeps it, I would love to get the frame. All you need to do it is fillet it, put the frame in a plastic bag, and either give me a call (0439796609) or send me an email (mangrovejackresearch@gmail.com). I will collect the frame at a time and place convenient to you.

Thanks for reading, and feel free to contact me if you have any questions about the research.

Cheers,

Toby

[Leaping bonito]

And here is a pic of a jack (from the Clarence River) fitted with an acoustic tag being released. Unfortunately, we know that at least some of these fish have been caught and killed. They are of course legal fish, and I can't really do anything about them bem being kept. However, in the long run, these fish can hopefully provide us with a lot of information on jack movements, so it would be excellent if they could be released.

Cheers,

Toby

[chris69]

Surgery on jacks now ive seen it all............... well done Toby........,its a pitty about the ones caught its a bit of a waste of time for you and delays your research and chews your funds,a tag saying DPI reaserch please release would be the go,cheers chris.

[tunaticer]

What data does your accoustic tags deliver to the sensors??
Is it just as it passes a sensor or does it include max and min temperatures, depth maximums, and blood pressure or whatever?
How many pickup beacons have you got installed and are they in fixed locations or moved about to cover an area?

Are there any gps tags that are insertable and reliably work that could be used?
That tracking would be huge data windfalls if they can track underwater.

[Leaping bonito]

G’day TunaTicer and Chris

The acoustic tags I’m using transmit a unique 4-digit codeto the receivers. You can get tags whichrecord other info, especially temperature and depth, but mine just tell youthat your tagged fish was within reception range of the receiver. I went with the straight presence / absencetags for a couple of reasons. First,they will give me a longer battery life (since the temp / depth loggingfeatures require extra power). Second,they are also considerably cheaper, and it makes my funding go further and letsme tag more fish! With the tags I’musing, I should get about two years of movement data from the tagged jacks.
The reception range can be up to about 300 metres radiusaround a receiver, although in practice I would expect to get less than this,since factors like suspended silt in the water tend to reduce signalstrength. Also, reception tends to bereduced in depths less than about 25 or 30 metres. The reception ranges for my receivers won’toverlap, but in practice this doesn’t really matter, since I’m not aiming forreally fine-scale movement data. Themain aims of my project are to detect movements between estuaries and offshorehabitats, and to get a broad picture of movements within the estuaries. There would, however, be another greatproject based on following tagged jacks around with a mobile hydrophone andgetting that really fine-scale movement info.

My receivers are all fixed in place on the riverbed. They look like a black plastic cylinder,about 40 cm long and 10 cm in diameter, with a cone-shape on one end (this isthe actual hydrophone, which detects the signals from the tags). In areas close to the estuary mouths, wherethe tide runs hard, they are attached to the bottom by car tyres full ofconcrete. Further upstream, they are on20 kg concrete blocks. The receivershave to be retrieved off the weights for downloading every six months, and Iwill mainly do this by diving for them.
Most of my receivers are placed about a kilometre apart,from the mouth heading upstream. Theexception to this is the two receivers closest to the estuary mouths, which aremuch closer together (200 – 300 metres, depending on the estuary). This set-up helps to determine whether taggedfish are entering or leaving the estuary. If a fish is detected on the receiver slightly upstream of the mouth,and then on the one right at the mouth, he is probably heading out to sea. Likewise, if you get him on the one right atthe mouth, and then on the one just inside the mouth, he’s probably coming intothe estuary from the ocean.

The set-up I’ve described is for my two smaller studycreeks, which each have 11 receivers in them. My other study estuary is the Clarence. In this river, I’m relying on NSW Fisheries receivers already in placefor monitoring other species (mainly bass and bull sharks).
There are small, implantable tags which records GPSdata. I must stress that I am no experton these, but as far as I understand, they rely on a vessel with asuitably-equipped Simrad sonar to be in the vicinity of the tagged fish. The vessel’s sonar transmits positioninformation from its GPS into the water, and this info is picked up by thetag. The system relies on the fish beingrecaptured and the tag returned to the researchers. In addition to this, there are the much large‘pop-up’ tags which are fitted to marlin and sharks. The fish carries the tag around for a certainlength of time, after which it comes off, floats to the surface, and transmitsits GPS data. You can see more about thesmall, implantable GPS tags here:

http://www.simrad.com/www/01/nokbg0240.nsf/AllWeb/41928D8F24E97689C125714C004A31F4?OpenDocument

Chris, my tagged fish all have a plastic tag in theirshoulder saying they have a transmitter fitted, but I reckon you’re right – it shouldalso include the words ‘Please release’. Unfortunately, it seems that the people who have kept the fish wereaware it had a transmitter, but chose to keep them anyway, so it may not domuch good. Worth a try though.
Thanks for the interest in the project. Feel free to give me a yell if you have anymore questions, always happy to talk fish!

Cheers,

Toby

[chris69]

hi Toby yer i find it interesting ive put in frame for research up here in Qld and found the the time of year we catch them is when the large ones are ready to breed,one i put in was ripe mature at 50cm at 5years,so it would be good to have a not take at a certain time of year like the barra closures,in my area there has been a big decline over the last 10years or more with population increase and the yak fad giveing easyer access to hard to get to spots,as you no you cant stop it,keep up the good work,cheers chris.

[cormorant]

another study using tags from tassie

play the video

http://www.abc.net.au/landline/conte...2/s3550676.htm

[Leaping bonito]

Thanks for the replies. Chris, that's interesting that your 50 cm jack was mature. That Qld jack study was a great project, very comprehensive. Do you mind if I ask whether your jack was an inshore or offshore fish?

[chris69]

Inshore [creek] Toby yes i found it interesting as i thought they went out side to spawn.

[Leaping bonito]

Thanks Chris, that's interesting. I was just reading the 'reproduction' section in the Queensland report. They found that spawning does take place offshore, and most inshore fish are immature, BUT, with fish being the unpredictable critters they are, they still got some mature fish inshore (just in smaller numbers than offshore).

[chris69]

Hi Toby yer there an interesting fish i had one in a lock that i just could not catch definatly hooked before and lived under a pontoon it could shake the bait off a hook and not hook up weither it was dead or alive bait and stingers in different positions i never thought id meet a jack i could not get but this one was the one lol, there very robust fish ive caught 2 with hook hanging out the anus, a little suicide with the eye of the hook worn away it had been in it for so long and 8/0 stainless covered in a crust from its digestive juices, nothing slows them down.

[Leaping bonito]

That's crazy about the ones with the hooks. We've found the same with the ones we've kept in tanks at works - quite a few of them have got rid of hooks in various shapes and sizes after being in the tank for a little while. My boss has kept a lot of different fish species in the tanks at work, and he reckons the jacks were the most hardy and curious. Often we'd catch one at night, bring him back to the tank for tagging, then when you checked on him the next morning, he'd swim up and have a look at you! Most other fish would be over on the other side of the tank and not come anywhere near you. They are definitely smart, curious and alert fish. That's really interesting about the one you encountered who seemed to learn to shake the baits off. Fish are amazing critters alright.

[chris69]

Hi Toby my mate had a fresh water tank and go a jack only small at first 50mm then when he got a bit bigger he started feeding him little guppies i use to love visiting and feed the little bugger ,id put 3 in the tank and it would chase them around the tank attack 1 and then another and go for the 3rd with its mouth full and it use to spit the last one out did not eat it just wanted to kill it,it was fascinating to see it light up when it got excited,after awhile it go bigger and was giveing his archer fish a hard time like a bully at school but i think it was board, so he gave it to his stepson well,in a mounth it had killed the bass and cod all bigger than it and died by chocking on a brissel nose catfish it was a terror from birth i think but thats the nature of the jack i think and yes it was allways curious if you tapped the tank it would come over and look at you.