The mangrove jack is one of the most revered fish in Australia! This is for good reason as not only are they stunning, highly intelligent fish, but they are strong spirited dogged fighters, excellent eating, have an interesting behaviour, complicated life cycle and a lot of personality. A fish with predictable habits, the mangrove jack is often very high on many an anglers wish list. Below is some information on the Lutjanus argentimaculatus, written mainly from an estuary basis!

The mangrove jack

Above: Typical larger FNQ saltwater mangrove jack taken at night

Mangrove jack are a member of the Lutjanus family and are a Snapper. They live in freshwater, brackish and saltwater both estuary, inshore and offshore. They grow over 1 metre offshore and typically move out of the estuary system when they become 50-60cm. In areas such as South East Queensland they tend to stay in the estuary longer and grow to a larger size by around 10cm.

While it is unknown why they grow larger down south, it is believed that because they are the ‘top dog’ in the estuary they stay longer. Also with more ‘reef’ like structure their needs are met for longer in the estuary. Typically a common large estuary mangrove jack from South East Queensland & Northern New South Wales will be over 60cm, while in Central and Northern Queensland over 50cm is considered large. Exceptions to this rule do stand with larger fish being caught near river mouths during breeding season periods.

In freshwater environments they can also grow large if there is abundant food sources. Mangrove jack stocked into dams and lakes can grow very large sizes, even larger than your typical freshwater or saltwater estuary fish.

They have large eyes with excellent sight. When over sand their body colour is usually more pale bronze and when over rocky bottom or heavy timber they will be a deep red, they can be green bronze, deep red, pink and all colours in between. Juvenile mangrove jacks are very pretty and have a pretty blue line on their face and striped body.

Why are they so awesome to catch?

For that unmatched powerful initial run towards it’s lair. With line snapping power, when a large mangrove jack hits your lure or bait there is little doubt as to what species it is. Mangrove jack hit very hard. Almost always hitting the lure or bait head first, they smash grab and run hard for home. If the angler survives this initial drive the odds of landing the fish are greatly increased. A dirty fighter the mangrove jack will always find structure to bury lines in and anglers must always be on their toes to gain the upper hand and land the prized fish. Catching a big jack (or even being busted off) will often leave the angler shaking at the knees with pure adrenaline.

Above: A healthy medium sized jack taken in the mangroves

Mangrove jack are also excellent eating, especially when killed quickly, bled well and iced immediately. While the catch & release trend is very popular for these prized fish, especially in southern regions, in the tropical areas they are common table fare and in relative abundance. Personally I release a lot of them and unless they are over 40cm I don’t keep them.

Where are they found?

Located throughout the Asia Pacific region, mangrove jack are found throughout south-east Asia, Papua, Oceania and Northern to Central Australia.

The mangrove jack starts life in the saltwater as a hatchling, it then swims upstream in an estuary until it locates a suitable ‘snag’ to live in. This snag becomes it’s home until it becomes mature enough to go out to the headlands to breed, then eventually out to sea to become a large adult.

How to catch a mangrove jack?

Mangrove jack are opportunistic feeders and eat almost anything. Favourite items include prawns, crabs, oysters, yabbies, herring, mullet, basically anything that swims. They will attack most prey head first taking one large swoop engulfing the item whole. If the prey is too large they will immobilise it with solid blows to the head and body and slowly keep at it until it’s swallowed whole or in pieces. Sometimes they will pick at a bait, usually when suspicious of the offering and can be hard to catch during these times. Well prepared bait goes a long way here. Keep the hooks small but strong and use as little sinker as you can get away with.

Above: A saltwater jack taken in shallow water over a sand bank mid morning on a handmade timber MD lure

There are a few different ways they will attack a bait or lure. Sometimes they prefer a lure, other times a dead bait, others a live bait. When they are aggressively feeding all will work. If fishing more than one line, mixing up live bait and dead bait can reveal what they want on any given day.

Lures: When lure fishing it’s usually a hard smash and grab followed by a huge power run, or sometimes it’s a very soft take that might even go unnoticed. It pays to always keep an eye on your line and if any movement is detected (especially side to side) the fish might have your lure in its mouth and best you strike hard when you see it to avoid the fish dropping the lure. This happens more with soft plastics than hardbody lures, but it does happen with both, especially on the ‘pause’.


Above: Lure size isn’t as important as the action

Mangrove jack hit many different types of lure, in fact there isn’t many lures they won’t hit! In general the best lures run just a bit lower than you can see into the water and are bite sized, from 40mm to 90mm with a nice action that suspend on the pause. Casting must be pin point accurate, you want it within 1cm of where you think a fish might be holding in the structure. Or better still run it past the structure getting down to the perfect depth. Soft plastics work wonders for this rigged weedless as you can let them sink and then twitch them through the snag getting the lure right into the strike zone. To get a strike from a mangrove jack you need to take advantage of it’s highly territorial nature and get your lure right into it’s home. A jack will usually strike at anything that comes near it as long as it’s not suspicious. Although highly intelligent, this territorial aggressive nature is their weak point and this needs to be fully exploited when casting lures.

Using a lure that gets down just past where they can see you is important in high light conditions, during low light shallower lures can be used. Exceptions to this rule include shallow lures twitched hard to look injured across nasty fallen timber and snags might raise an angry red fish from the depths, but your best bet is usually to get the lure down to them. Generally mangrove jacks sit very tight to structure, but when actively feeding they can be found anywhere, especially at night. They will sit in very heavy current and often in shade to gain the advantage of prey not seeing them. Mangrove jack can also be found in extremely shallow water on sand flats, usually where there is a decent amount of bait and current, usually with good access to deeper water.

Bait: As with lures, the take varies. Sometimes they will play with live baits or even dead baits and be very cautious or just plain cruel. This often fools the angler into thinking it’s a small ‘picker’ fish, when in fact it might be a quality jack. When they are being tentative, it pays to be patient and ready, when they go, they GO! Striking too early and moving the bait can put the fish off the bite and it’s best to just be patient, even if that means re-baiting hooks. If ‘pickers’ are a concern, then use larger baits, hooks, or better still live baits. When they are comfortable, especially bigger fish late at night they will hit and run so fast it’s best to keep your rod in your hands and be very ready to stop it getting home and busting you off on the nearest piece of structure. They can hit fast and hard and sometimes on the drop of your first cast, so be aware and ready (a common theme hey!).

Typically you will feel a very light but definite ‘tap’ – ‘tap’ if you feel this get ready and be patient, this is the typical jack attack on dead bait but also sometimes live bait. Generally the bigger the ‘tap’ – ‘tap’ the bigger the fish, or more confident, however this rule is not always applicable when they are suspicious or ‘picky’ feeding. Unless you are in open country, always hold the rod, or if patient position your bait slightly away from structure to gain a better chance of stopping them. Staying very quiet always works wonders and will allow the larger smarter mangrove jack to be caught off guard! Stealth mode is key.

Dead baits: Fresh prawns, mullet, herring are all great dead baits. Also chicken, squid, nearly anything will work, however if they are picky, fresh is always best. Butterflied presentations always get attention and a slice of mullet can be the only answer when live bait and lures don’t work.

Live baiting: Prawns are usually the best bait, use as lighter leader as you can manage and a small strong live bait hook rigged sideways through the last section of the tail. Small mullet & mud herring also make good baits, rigged through the back near the lateral line not too far into the fish to ensure it lives. Be sure to change the water in the bucket at least once when using prawns and herring, and use a good aerator to keep them alive longer. The quick and gentle transition from cast net to bucket helps the herring live longer!

Above: Brackish mangrove jack caught on an IMA sasuke 75 slow sinking lure

Trolling: Trolling is an effective technique, using around walking pace, or just faster for best results. Lures that swim at sounder depth is best and sticking loosely to the structure on the river banks is a good idea. As with cast and retrieve, if you’re not snagging some lures, you’re not fishing close enough to the structure!

How to land a mangrove jack

The harder you pull, the harder they will – this becomes difficult when you are dealing with fish that are hard to catch and making powerful runs for home while amongst ‘tiger country’. If this is the case, the best plan of attack is not to try and rip their heads off in an attempt to turn them as the added force will put a lot of stress on your line, knots and the hooks in the fishes mouth. Likewise if you have your drag totally locked, the initial impact of a large hard hitting fish will bust your lure off at the knot, straighten hooks, or break your leader knot. You want to have a little bit of give in the system, so almost locked drags are better than 100% locked drags. The aim is to guide the fish turning it away from home rather than muscling it. You will still need a lot of stopping power but it’s more in how it’s done than the strength of your gear. Sometimes however, you just have no choice but to lock (the drag) and load, then you just have to take what you get, usually a bust off and shaking knees!

Above: A mangrove jack taken on a MD lure

Drag Settings

Getting the drag just right is crucial when fishing for jacks. Too tight and you’ll get busted off by big fish, too loose and you’ll get stitched up in a snag. You want the drag set quite heavy when lure fishing, yet light enough to soften the hard hits. Sometimes you have no choice but to almost lock the drag and always set it just a bit tighter than you think is enough, I can’t count the amount of times fish have surprised me by taking line on almost locked drags. It’s a fine balance. Generally tight enough to just pull line off the spool with some effort. Nearly locked would be tight enough that the braid isn’t far off cutting into your hand, a big jack will still take a good run even with the drag set this tight. Naturally if you are fishing light, you’ll need to set lighter drags.

When bait fishing in open area I run very little or no drag, usually on a bait runner. When the bait picks up speed, I strike the fish and run a fairly tight drag.

What sort of gear is needed to land a jack?

I know serious anglers that fish the Gold Coast using 50lb main braid, 80lb leader and huge barramundi lures to catch the biggest brute jacks in the estuary. There are also anglers that use bream gear with silly string that are happy to lose the bigger fish but get more hits and land more fish (sometimes). Spin gear, bait casting gear, doesn’t matter. Typically there are a few levels of gear, depending on where you are fishing, what style of fishing and what you want to actually land!

Large fish: Medium heavy rod with 20lb braid and up to 40lb leader, should land nearly all jacks with smart angling. Remember to go easy and guide rather than pull too hard. Lighter leader will get more bites. If fishing for southern mangrove jacks consider having heavy gear (suitable for barramundi) if you’re getting stitched up!

Medium Fish: Medium to light gear, 8-16lb main line with 8-20lb leader. With lighter gear it will be touch and go stopping that initial run close to structure as you will be under gunned to turn the fish away from home. Medium light (12lb braid, 2000 size reel, 12lb leader, 4-16lb rod) setups are the most fun as it still gives you the stopping power to catch bigger fish and really keeps you on your toes when hooked up to a beast of a jack! Knowing you have little reserve should a good fish hit helps the angler stay focused and can really increase the enjoyment.

Little Fish: Bream gear will stop most little jacks even some larger jacks. Smart angling really comes into play here, as well as good gear and drag settings. You can land jacks over 60cm on 3-4lb straight through fluorocarbon, however you need to be very lucky and find fish feeding well away from home and any snags. Using very soft hands goes a long way here and a bit of luck as well. You will get more bites with light gear and many, many bust offs!

When fishing with live bait, an overhead, baitcaster or bait runner is best.

I think it can be wise to try different set ups and see what works for you. I know anglers that fish heavy rods, lines and drags that frequently get busted off. I’ve also seen anglers fish way too light and constantly get busted off, hooking lots of fish but landing none. No point taking a knife to a sword fight, nor a bazooka.

Anyway that’s my take on mangrove jack fishing, feel free to suggest anything that’s missing, or ask some questions in the comments below.