From estuary to reef, this is a favourite target in the north of Australia, writes Colby Lesko
Mangrove jack are one of the angriest fish in the estuaries. I don’t think any other fish in the estuaries that rival their speed and hitting power. Jacks will smash your lure off the surface the second it lands and run for cover with exceptional power for their size. That’s why many anglers chase them, losing plenty of tackle in the process. Jacks have a huge distribution across the north of Australia, spreading from the north coast of NSW all the way to the northern half of WA, making them available targets for many anglers. The jack has an interesting life cycle, starting life in the estuary before moving offshore.
Mangrove jacks start their life in the estuaries of northern Australia, where they live their juvenile life until they outgrow the estuary then move offshore. But this isn’t always the case and many of the bigger estuaries are an ideal home for the large jacks, and bigger fish over the 60cm mark can still be caught in the estuaries. The southern estuaries of the mangrove jack’s distribution range seem to have a more seasonal summer fishery for jacks while the northern estuaries hold great numbers of jacks all year round.
However, most bigger mangrove Jacks (60cm-plus) move offshore onto coastal reefs or coral reefs in 20 to 100 metres of water. Mangrove jacks mature at around 50cm long and at this size often move offshore. Adult mangrove jacks spawn in offshore waters so it seems this is a driving factor to push the bigger fish out of the estuaries and into the ocean. Big offshore jacks are often referred to as reef jacks and still have the hard-hitting and great eating qualities. Mangrove jacks are a long-lived species with a few fish over 50 years old!
Targeting mangrove jacks in the estuaries is loads of fun on light gear. Mangrove jacks love structure, and by hiding under cover are able to explode onto unsuspecting prey that moves past. By fishing structure such as rock walls, sunken trees, bridges, wharfs and pontoons you can give yourself the best chance of running into feeding jacks. Jacks in the estuaries feed on prawns and smaller fish so a mixture of lures will work. Paddle-tail soft plastics and surface lures are my personal favourites, but vibes, prawns and jerkbaits are also great options. Try to match your lure to the size of the bait in the system – something between 3 and 5 inches is usually perfect.
Light gear such as your bream or bass combo (2 to 5kg rods, 2000-size spin reels spooled with 10lb braid) is perfect for accurately casting small lures into the jack snags; however, you may need to go heavier depending on the size of the jacks. If 10lb leader isn’t cutting it and you find the jacks are busting you off, you can up that to 15lb or 20lb to help you pull the bigger fish out. But sometimes the really good fish will need a heavier combo such as a 4 to 8kg rod matched with a 3000 spin reel spooled with 30lb braid such as a soft plastics for snapper combo.
Go as hard as you can once the jack hits your lure and try to prevent them from running back into the structure, where they can cut you off. They will use this structure that’s often covered in barnacles and oysters to shred your line and win their freedom. Jacks are often in small groups or schools so if you catch a fish from one spot, it’s worth fishing that area well. You can move through areas extremely quickly when fishing for jacks as it will often be the first cast on that particular area or snag that the jack will bite.
Bigger snags you can work over with a number of casts but small logs or branches in the water often require only one cast. By covering more water and snags, you run into more fish. You can catch jacks at any stage of the tide but my favourite time by far is the bottom half of the run-out tide when all the bait fish and prawns are pulled out of the mangroves or flats by the tide and past the snags where the jacks are waiting. Jacks will hide in snags in the shallows only one or two feet deep but they will also be out on the deeper snags, so all structure in the water is worth a cast.
The best snags are the ones where the jacks can wait in the cover and protection of the snag and have the tide or current bring the baitfish to them. Jacks in the estuaries can be caught day or night on lures and have no problem smashing a lure on the darkest of nights.
Targeting offshore jacks requires a different approach from fish in the estuary. Offshore jacks seem to lose their aggression towards artificial baits and are nowhere near as receptive to lures as fish in the estuaries. Sure, the odd reef jack does get caught on a jig every now and again, but relatively few given how many are out there. This may be because these older fish are simply smarter than the juveniles but who knows. Once the fish move offshore, they seem to stop taking lures anywhere near as much and are a much more viable target for bait fishing or spearfishing.
Reef jacks will take a variety of live and cut baits. They prefer to hang on big drop-offs and heavy structure such as large bommies with caves or reef edges. During the day reef jacks will hang close to and inside this structure and I often see schools of them hiding in the cracks of reef while I’m spearfishing. At night these fish move out of the structure and cruise around looking for a feed. The best way to catch big reef jacks is to bottom bash with fresh baits in 30m to 80m of water at night.
Target drop-offs and reef edges, or patches of rubble with reefs close by. Wrecks are another hot spot for offshore jacks. Reef jacks fight extremely hard so a PE 2 to 5 bottom fishing set-up with 60lb to 80lb leader is usually needed to get the fish up out of the structure and away from the sharks. Reef jacks are commonly caught in the 50cm to 80cm range but can grow over a metre long – serious fish! Reef jacks seem to be targeted a whole lot less than the fish in the estuaries and most jacks are caught as a bycatch when fishing for reef fish such as red emperor or nannygai.
The mangrove jack is an interesting species of fish and an Aussie favourite in the north. Understanding the fishes’ movements and habits will help you catch more. So, keep the jacks in mind next time you head out and you never know what you might find.