Tags Fish Guide

Mangrove Jack

Tags Fish Guide
Category: High Risk

LUTJANIDS are renowned fighting fish. The genus is a big one and, besides jacks, includes red and spangled emperor and crimson and saddle tailed sea perch. Two things they all have in common is that they fight like a drover's dog and taste terrific.
Jacks, as they tend to be affectionately known, are one of the strongest fish encountered in our northern rivers, creeks and estuaries. They have a strong liking for oyster encrusted snags and rock bars and a capacity to get back from whence they came in the blink of an eye. It is probably fair to say that jacks have been the big losers with the advent of braid lines - lock up with your thumb and hang on! Not refined, but very effective if you want to get them out of their rugged habitat.
I list jacks among my favourite table fish and 1 recall fondly a feed of jack fillets I had at Walcott Inlet a few years back. Fresh and lightly dusted with self-raising flower, and pan-fried in a really hot cast iron camp pot with just a smear of cooking oil in it. Crispy on the outside, pure white on the inside with a wonderful sweet flavour and a fine texture. Served with boiled rice and a chilli sauce our guide had made up I recall it as clearly as yesterday. What a treat!

The rich deep bronze colouration has almost a metallic paint appearance to it. The only two species you could confuse a jack with are a red sea bass and a fingermark bream. But the bass has black fins and the fingermark, as its name suggests, has a black mark on its back. Juvenile jacks have quite noticeable bars on their sides.

Mangrove jacks grow to a size that will surprise some anglers. Mostly we encounter smallish fish up to 1.5 kilos in northern creeks, but jacks spend the latter part of their lives around offshore reefs and it's there that they reach huge proportions. Marine Fishes of Northern Australia lists weights up to 11.2 kilos - and that's one big mean jack.


The common range is from the Ningaloo Reef northwards. And as with so many tropical species it seems that the extremity of their southern distribution is where the biggest specimens are found. The Monte Bellos are noted for some huge lure-crunching jacks of eight kilos or more! However, there are small numbers of jacks down as far as the mangrove creeks at the eastern side of Exmouth Gulf, where sand flies and mossies do a great job of protecting them. Though anglers generally encounter jacks in creeks and around shallow rock formations, they have been found in depths to 120 metres when they move offshore. When seeking jacks start by looking for structure -they are rarely far from it, and the harder it is to fish the more jacks like it.

Breeding and migration

There has been little research on this species and all we know about jacks' breeding is that they lay their eggs in open water during summer and given that the mature fish live on the offshore reefs it is assumed that breeding takes place there. Jacks reach sexual maturity at four to eight years and at about 55cm in length. Their lifespan is an amazingly long 32 years and more recent indications from research is that they may live as long as 45 to 50 years. This generally means that the jacks encountered by recreational anglers in northern creeks and around mangroves are immature specimens. They feed on prawns and crabs and just about any fish they can fit in their cavernous mouths. However, they are reluctant to leave their lair, preferring to lie in wait and ambush prey that passes with the changing tides.

Other than some potential for recreational overfishing close to populated areas there are no known threats to mangrove jack, although intense trap and trawl fishing around offshore reefs could well pose a threat. Potentially one of the most threatening challenges for mangrove jacks would be loss of habitat through the destruction of mangroves, which happily is not a big issue currently in Western Australia.

Tackle and bait
My biggest jack was caught on a 15-kilo short stroker outfit when bottom fishing for bigger fare, but the two most popular methods are casting lures and baits. I prefer to cast lures on a small baitcaster loaded with 10kg Platypus Super Braid. In fact I use the same outfit for bait fishing too. Bait rigs should be simple because hook losses among the snags in jack territory can be quite high. A sturdy Mustad Tarpon or similar tied to a mono leader with a ball sinker running down to the hook is the way to go. Whatever bait is prominent locally will be fine, but at times jacks will hit just about anything. Lures are generally smallish - around 12cm maximum. I use very sharp hooks but I crush the barbs on trebles. I don't believe it affects my hookup rate and it's easy to release a feisty jack at boatside. My favourite jack lures include Tilsan Barras, Spearheads and Flatz Rats.

Fishing methods
Find structure when fishing tidal creeks and if you're in luck the jacks will be there. Having said that, there are occasionally snags which have jacks written all over them but in fact are home to just small GTs or queenies. When casting lures you frequently have to live dangerously and get in tight to a snag or rock face. You have to accept that jacks will simply refuse to leave their ambush spot to whack even a well-presented lure. I favour twitching the rod tip and winding only half a turn at a time to keep the lure in the strike zone for as long as possible. Occasionally a jack will hit a sitting lure cast in tight to a snag. It's the same with baits - get them right in there and hang on!

Allan & Swainston, The Marine Fishes of North Western Australia. Compiled with the assistance of Fisheries WA, Research Division.
Older Post
Newer Post
Mahi Mahi