Jacks changing their colours

[Pete62]

These 2 fish came out of the same estuary in the same season, I know they can look different but I am guessing the very dark fish had been in the creek for a long time and the lighter fish may have come in from sea more recently. Thoughts? Pete.

[Didley]

Hi Pete, I got nothin Mate, but I'll start the ball rolling 4 ya. I reckon U'll find the dark one has come out of a rock crevice or something, the silver has been roaming over sand perhaps. See I got nothin. MJ can change colour quickly. They'll change between getting them out of the water and release from silver to red. Talk to someone who's got them in a fish tank I believe they light up when a feed is on the way. I think u'll find they red up with the equivalent of an adrenalin rush, so they tend to be to at the redder end of the scale when U catch em.

[nitroburner]

Gday Pete, im no expert but maybe the darker one is getting ready to think about heading out to the reef . The jacks that i got up in NQ on the reef are a real coppery bronze colour and they are awesome to look at . Tasty too.

[tunaticer]

I think its partly to do with their territory they nest in and partly to do with thier attitude. Often times not just with jacks but many species you can notice changes in colour from before it is netted to once it is in the boat then a change again when you are swimming it for release. They might be just shades they change but it is noticeable if you look for it. I put that down to thier panic levels being in a deadly environment out of the water and starting to suffocate.

I would also suggest that the lighter one is more "pelagic" in that it probably does not have a favorite snag to nest in and roams the open water a lot more. I have caught several jacks up north that have been 500m or more away from any forms of snags out hunting the tidal flats, nearly all of those have been lighter shades.

[banshee]

How far was the green fella from fresh?In CQ I sometimes find them in sweet water and they are always green.The first pic shows one that came out of water that I drank,the second one came from decidedly brackish/salty a good distance down close to where the creek ran into a tidal creek.

[UNCLE NUGGY]

Pete62,
were they caught in the same month
was the lighter cloured one caught after heavy rain at the start of the year
all the silverey ones ive caught have been after big rain when the water is still pretty fresh.
cheers
UN

[snatch]

My guess is the lighter fish is from up in the fresh. They run up there to spawn and some hang around if the food is there.

[banshee]

My guess is the lighter fish is from up in the fresh. They run up there to spawn and some hang around if the food is there.

Tend to dissagree with your thoughts on spawning,my understanding is that they stay in the estuary 'till they mature then migrate to an inshore reef to spawn where they stay and generaly work their way around the reef systems sometimes finding their way to the offshore systems.The fry/fingerlings then make their way back into an estuary to start the cycle again.

[Didley]

I'm with banshee on that one.

[485hussar]

I agree, lighter from the freh, darker from esturies/ sea with darker/ deeper water maybe

[Cobia Kid]

I heard that Jack travell in schools of like 20 when going a long distance....say to the reef,
any truth behind this,
nice fish anyway man,
cheers

[UNCLE NUGGY]

Tend to dissagree with your thoughts on spawning,my understanding is that they stay in the estuary 'till they mature then migrate to an inshore reef to spawn where they stay and generaly work their way around the reef systems sometimes finding their way to the offshore systems.The fry/fingerlings then make their way back into an estuary to start the cycle again.

i read somewhere that they mature at 2yrs around 40 cm
just wondering if you had any info on this??
cheers
UN

[banshee]

i read somewhere that they mature at 2yrs around 40 cm
just wondering if you had any info on this??
cheers
UN

Sorry UN but that's all I got,I have caught them up to 57cm localy (Nth NSW) and I've also seen one that was presented at a tackle shop that went 24lbs back in the early '80's at Ballina, but I'm prety sure that the lagoon this one came out off was land locked by a training wall.

[Pete62]

Hi guys, it's a good debate, with plenty of opinions, all have some weight. banshee & UN both fish came off snags within a k of each other about a month apart ( mid Summer) quite a way upstream but water was still quite salty. I am sure that they do move out to the reef on maturity to spawn but strangely very few r caught at sea around here ?? They seem to be a common catch up north but around here 99% come out of the creeks. The red fella is my biggest 3.5kg but I have been totally humiliated by fish I had no chance of stopping, geez they can pull can't they. pete62.

[childers]

pete 3.5 kg thats just under 8 lb !, how many cm would that be ,passed through your way at chrissy ,local boys said giant jacks hanging out at the boat harbour ,and plenty unstopables even on the xxx heavy gear ,not sure about the color thing ive caught two five mins apart ,same spot different shades,cheers.