The mangrove jack (Lutjanus argentimaculatus) is one of Australia’s favourite fish.
Though primarily of northern waters they have been caught south of NSW’s Sydney Harbour and are found in WA’s Shark Bay.
Jacks have been described as a resident of snags, and an aggressive lure taker, and it is true they are often found around submerged timber, mangrove roots and rockbars.
However, studies show they can be highly mobile even before they leave estuaries as adults, moving up and down the coast.
Jacks begin life on reefs some distance from shore, out beyond the 70m zone, where the adult fish spawn.
The young mangrove jacks swim to the coast, perhaps attracted to freshwater flow, where they make their way into rivers, tidal creeks and estuaries.
They can live in fresh and salt water, and adult fish have been stocked in some Queensland dams.
It is the juvenile mangrove jacks, before they reach 1kg or so, that are most often encountered by anglers.
Jacks leave the estuaries from around three years of age onward, and take up residence in deep water, to repeat the cycle.
Being tropical fish, mangrove jacks are best targeted in summer in the more southerly extent of their range.
Catching mangrove jacks can be as simple as lobbing a lure at fallen timber or a rockbar or rock wall, but these fish have good eyesight and will often just make a pass at a lure.
It is the author’s experience, having used two types of tropical herring as livebaits at the same time in a Cooktown creek, that the fish can be fickle.
They turned their nose up at live brown herring and only took the live blue ones. Lures and dead herrings at the time were ignored.
This fickleness was then repeated fishing a weir in Cairns, where only live mullet were taken, with dead mullet and lures ignored.
Fishing around Darwin, mangrove jacks would sometimes our take deadbaits in turbid creeks, but the bigger numbers of fish were found in clear sandy creeks away from the turbid areas where they would only take lures if in the mood.
That said, lures will at times catch mangrove jacks one after the other, and the author has caught many like this in creeks and along rocky foreshores within bays, on the rising tide, and also along mangrove root edges.
To improve your chances, find a remote creek or an arm of a creek that is not much fished, gather livebait, and set your bait near structure.
Rocky foreshores and rock walls often hold fish. On a rising tide they will hunt in just a few inches of water, perhaps looking for crabs.
While remote creeks invariably fish best, mangrove jacks show up in hard-fished metro creeks as they are mobile fish, but large congregations of fish will be more easily found in remote creeks, especially in the far north.
Small tidal creeks on remote islands are often productive.
Jacks have sharp teeth. Use hard nylon line leader rather than wire, and use a fine long-shanked hook around size 3/0 for livebaiting.
Use very small minnows or soft plastics, and a touch of bronze and red seems to work well for lure colour.
Jacks invariably head for snags when hooked, so try not to give them line.
Jacks are long-lived, growing to an impressive 120cm or so.
They reach almost 40 years of age.
On the wide grounds, which may be over reef or rubble, the big fish are usually caught at night using standard reef fishing methods.
Jacks are good to eat and make an impressive whole-fish dish, especially when served with mud crab pieces on the side.
Read more about mangrove jacks.
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