Figuring Out Catchments – Dan Kaggelis 2017

North Queensland is blessed with some amazing waterways filled with equally amazing fish species. The reason for this piscatorial richness can be attributed to our diverse and mostly unspoilt catchments. Catchments can best be described as natural landscapes which collect and channel rainwater.

They are characterized by an upper, middle and lower tract. Unbeknownst to most anglers, the health of catchments is probably the single most crucial factor in the determination of a sustainable inshore fishery. Some of the more predominant NQ catchments across our state include the Burdekin, Herbert, Walsh, Mitchell and Wenlock.

However, the further north you travel and the closer the ranges get to the coast you can find some catchments which are less than 20 kilometers long and can be fished from its upper reaches to its coastal mouth in a day.

From an angling point of view, catchments provide the highways for our most prized fish to recruit, grow and breed. Understanding the different tracts of a NQ catchment is an important skill for those wishing to tap into some of the awesome fishing options they offer.

Whilst upper, middle and lower tracts can hold the same species of fish they can be very diverse and therefore require different approaches and techniques. Let’s start with the upper tract.

Upper tracts of catchments are where many systems begin and are commonly found inland in gorge country where they begin as freshwater streams fed by constant mountain rainfall.

Upper tracts are recognizable by steep vertical like cross sections of river due to erosion caused by their fast flow during high rainfall. They are mostly recognizable by features such as water falls, massive boulders and gorges.  These areas are the least fished parts of a catchment as they can be hard to access due to their remoteness and in some instances, can take days of walking to reach.

In the very upper reaches of catchments the water temperature is bitterly cold even in tropical climates as it is pure fresh rainwater which has had little time to settle and warm. Due to the extremities of upper catchments only certain fish can survive its ruggedness especially during high flows where fish run the risk of being battered against rocks.

Looking at the characteristics of several of our native species you can easily see how many have adapted to meet these extremes- none more so  than the Jungle perch.

The upper catchments are where Jungle perch thrive as there are few large predatory fish that can survive in this area. Their hard armor like scales allows them to survive being smashed again rocks and to traverse fast flowing rapids.

In these areas JP love to sit at the heads of pools in the white water waiting for small shrimp and fish to tumble down. Their large eyes make for amazing eye sight which can pick out the smallest morsel in this bubble filled environment.

When chasing JPs in this country it is best to use this approach, letting the flow of the water take your lure into the strike zone by casting above the rapids and letting it float down.  The key is to keep your line tight enough for when they smash it off the surface.

Sooty grunter are also found in the upper tracts of most catchments and whilst their scales are not as tough as the JP their stocky build and muscle provides plenty of cushion.

Many sooty’s found in the very upper tracts of catchments are amazingly strong and great fighters. In these areas, they tend to seek out the deeper pools or holes away from the white water, seeking refuge under rock ledges.

In this scenario, a sinking or suspending deep diver or plastic is an ideal presentation.

Moving between the upper and middle tract is obvious as the steepness and gradient begins to lessen. What you will also notice is that the size of boulders will begin to reduce dramatically as you move away from gorge country into smaller riverine style areas.

As the gradient begins to lessen streams tend to become wider and slower flowing with less rapids. The middle tract of a catchment is where many species interact and can provide some huge diversity.

The apex predator of the middle tract is certainly the barramundi as they use these middle tracts during their adolescent years to grow and mature before moving back down into the lower catchment to spawn. Jacks are also found in middle catchments as well for the same reasons.

As in the lower catchment, barra and jacks love to hang in structure although due to the shallow nature of middle tracts this does not just mean timber snags.

In middle tracts weed beds are prolific and these fish love to sit amongst the weed or behind small clumps waiting to ambush prey.

Almost impoundment like behavior is exhibited by middle tract fish and similar approaches should be used here.

Sooty’s are also middle tract species however tend to be more of the upper middle not lower middle as they are not salt tolerant.

In the middle tracts, sooty’s tend to utilize their dark colours as camouflage and prefer to sit in structure in the shade.

Khaki grunter a variety of sooty go as far as to change their scale pigmentation to match the leafy bottom structure in slower running sections of middle tracts.

Therefore, anywhere you can see shade or dark bottom is a good spot to work a lure when chasing these fish. JP are also found in the middle tract of NQ Catchments but behave a little differently.

Whilst they still love to hang in the whitewater, when these areas become less frequent they begin like the Sooty to rely on their scale patterns for camouflage and hunting. Middle tracts of NQ systems tend to have a course grainy sand bottom mixed with pebbles and this matches perfectly with the colours and scale patterns of the JP.

They can literally sit out in the open and be almost invisible. Therefore, big long casts across open slower running sections of water is just a promising idea when chasing JP in these sections.

The one consistent rule for fishing middle tracts is always target bottleneck areas.

These include bends choke points and rapids as this is where all species love to hunt.

The final tract of catchments is the lower tract and this begins when fresh begins to move into salt, also known as brackish water.

These are amazing places to fish as you can be up a creek banging snags amidst some amazing freshwater rainforest and crystal-clear waters. Systems like the Daintree, Johnston and Russell Mulgrave are renowned for this special environment and should be a bucket list location for every angler.

Here in these areas the fishing can be a little tricky as they are not your usual estuarine environment. For one thing, the gin clear water makes it very challenging so light lines and leaders are a must.

High quality fluorocarbon like Sunline FC Rock and Sniper are a must if you are going to fool fish here.

Next the structure you are fishing is very different. Don’t bother looking for mangroves here as you will be fishing mostly under hangs or sides of creeks dense with rainforest foliage.

During the times of the monsoon it is not uncommon for these areas to include fish like JPs who move to the salt to breed.

This is where the lower tract tends to be at its best when the rain triggers the movement of larger adolescent fish like barra, jacks and JP from the upper and middle tracts to flush down to the lower salt reaches of the catchment ready to spawn.

Therefore, the lack of a wet season or a late wet can see a serious reduction in fish populations as the cycle is disturbed.

More importantly if middle tracts are targeted by commercial harvest this can see disastrous results as whole recruitment fish can be lost for years to come.

The many faces of NQ catchments are truly amazing fisheries and if you haven’t had the chance to traverse and fish the upper, middle and lower tract of a catchment you are truly missing out on an amazing angling experience.

Dan Kaggelis