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Tradie’s guide to fishing isolated structure

Fishing structure

What do deep holes, wonkies, detached shoals, bommies, wrecks and tiny coastal creeks all have in common?

These places represent isolated structure. Let’s take a deep dive into what constitutes isolated structure and why fish congregate around it.

Swirling currents

Just as science tells us small habitat size and isolation can promote species richness, so is the effect of isolated structure on fish habitat. In essence, a smaller geographical space containing structure can hold a higher abundance of life. As fisherman we search for this constantly: a hot bite!

A supercharged bite or a crazy session on certain fish will often have structure as its cause. As fish transition around their habitat, they inevitably arrive at the same feeding or breeding stations to try their luck, in the same way we gather at drinking establishments! 

Image: Tim O’Reilly

In a river, creek or stream environment, water moving past structure acts as a concentrating force to gather fish in a smaller physical space. The criteria to qualify as an isolated structure is pretty weak. Basically, it’s any object in the substrate which stands out distinctly, not attached to a larger mass or concentration.

Examples might include a large logjam sitting at the end of a long river pool blocking the rapids below, or a single large tree which has slipped into the river. A rock bar sitting on the corner of an otherwise muddy river bend would qualify, as would a tiny drain where wetland pours tannin water back into an estuary.

The structure may even be a narrow stream mouth, funneling water in and out with the tide, a soup of life entering and leaving.

Image: Tim O’Reilly

Know where you stand

For me, fishing any isolated coastal creek and sight casting predators pouring in with the tide is fishing paradise. Fish meandering out with the tide are just as good. Watching an undulating barra tail slowly nose past in the shallows is captivating, and touching a lure down in front of its eyes just seconds before the implosion is a huge thrill.

Taking advantage of isolated choke-points in a river system will likely yield results. Similarly, where two river systems interact, either converging or diverging, fish will congregate nearby. Think of this as having a foot in each door. Especially at periods of high tidal and river flow, isolated intersections provide a change-up to the flow, pockets of calmer water and often a steady trail of prey items. All those experiencing run-off fishing in The Territory, Cape York and The Kimberley understand these dynamics well in the never-ending quest for barramundi.

Nooks and crannies

The salt-fresh interface can be a major factor in all rivers around Australia’s vast coastline.

Normally defined as the area where saltwater intrusion on the tide high finishes, the pools in this area can be particularly productive, especially following a little rain and the recommencement of flow. These places are, in essence, isolated structure, different from their surroundings. Often a rock bar or bend in the river denotes a salt-fresh interface, and, of course, everything changes during the north’s wet season.

Image: Tim O’Reilly

Deep holes in a river or creek can act as reservoirs for fish to recede into after feeding or moving. If a deep hole is the only deeper area in the immediate vicinity, even better. At some stage of the tide, fish will congregate there. Getting them to bite can be a different story.

Especially in a creek or estuarine environment, many of these systems are super shallow at low tide. Fish are naturally forced to pull back into deeper pools, especially as a large low tide runs out. Vibes, deep diving lures and live bait will all extract predators from such places, a change in tide often triggering a bite.

Fish in isolation also tend to get hungry, especially when isolation is joined with competition. Competitive fish tend to feed harder and become a touch less fussy, and this is why you hear fishos talk about a rock they found out in the middle of the paddock (flat ground) that was surrounded by fish. Most likely all the fish there were looking for something to eat. You might have a school of fingermark, nannygai, cobia and trevally all swimming around the same rock out in the middle of nowhere.    

Not-so isolated

This is why isolated structure for the most part should be thought of in a slightly unique manner. Put simply, it’s best for everyone if these places remain fish bastions. Care should be taken not to extract too many for the table from one location alone. Only keep the larger specimens if you really need them, because these are the fish likely to produce the most offspring in spawning. Spread your efforts around.

Image: Tim O’Reilly

Shark behavior has also modified to zero in on fishers and prey in distress, so try and leave if this process commences.

Finding and fishing wonky holes – those isolated pockets out on the sea floor where fresh water seeps down from the mountain ranges and bubbles up from an underwater substrate – has become a thing in recent years, although the practice has been going on for generations. This difference or isolation from other such features is a gatherer in itself. It’s a different type of isolated structure providing shelter and nutrient-rich benefits for the occupants, a little microcosm in the aquatic abyss.

Hook, line and sinker?

One of the rules of thumb when fishing these confined locations is to be careful about dropping fish at the beginning. For some reason releasing fish does not seem to turn them off quite so much as dropping a hooked fish during battle. Those warning stress signals can carry to a school of fish in a millisecond, so fish diligently when you first arrive at an isolated hotspot. Have a plan of attack and a spare rig at hand if anything goes askew.   

Image: Tim O’Reilly

Fishy future

Lumps, bumps and shoals are classic examples of isolated structure and these areas produce more than their fair share of fish. Marine charts used to make this process of location a little circumspect, but with bottom contours, relief shading and bathymetry these days, things are getting a little more precise. Modern-day gadgets really get to the nitty gritty of all this, making looking for isolated structure that much easier.

Sounders are now powerful machines, capable of high-speed, accurate, bottom read and complex-structure analysis. It has made fishing deeper structure far more manageable, especially in vast paddock areas where isolates structure concentrates fish. Wonky holes are only the beginning to what keen anglers are willing to search for with modern gadgetry. Electric motors make locking onto these isolated patches that much easier. Besides being far more effective at anchoring on structure than traditional anchors, an electric motor with spot lock saves nearly all the physical exertion involved.

Image: Tim O’Reilly

Quite rightly, it fuels a silent debate about how much tech is enough. Following on from structure scan, the new live scope technology has probably taken it a tiny step too far for my liking (cue the boos). But I’m not the only one. All the salty old sea dogs are out there asking themselves, “Are we just setting this up for robots to take overfishing?”

The question needs to be asked. It’s alarmist I know! My issue with this tech is not with individuals using it, rather the effect I think it will have in the charter game. My scary vision is of guides spending more time looking down than looking up, and sad anglers believing they only have a chance of catching something when the guide tells them to. I see fishing losing some of its essence and if that happens, making it easier for people to diminish the activity of fishing as pure sport, rather than the hunting aspect fishing started out with.

Maintaining that aspect is a key to longevity. Taking away the right to feed yourself through your own exploits is a step too restrictive for me.

Let loose

The opposite side to this story is the growing number of individuals who are guiding around Australia’s coastline in increasingly smaller boats, often American-style flats boats capable of cruising and fishing shallow water. Some just cruise around the flats and shallow estuaries in tiny aluminium punts. Sight fishing or sight casting gladly has a rightful place amid the elitist sport fishing is becoming, and isn’t Youtube pouring the sight casting moments on thick and fast! I love it!

Image: Tim O’Reilly

Keeping things a little pure and simple definitely lets anglers reconnect with their environment. Even without all the tech, you’ll find astute anglers still know how to find the isolated structure. Using one’s eyes and other senses to locate and catch fish from a complex environment is one of the many challenges drawing in fishos. Understanding structure, as almost every fisherman knows, is key to fishing success. Using a little modern technology to locate where these areas might be is an irresistible urge to most – including myself.

Endless horizon

So where does our isolated-structure journey end?

After rambling off on so many tangents it’s hard to bring it all back to a common theme. Fishing isolated structure can be the difference between a mediocre day and a fantastic one.

There’s nearly always risk involved when fishing these locations, especially where travel is involved. With the fuel and time it takes, if things don’t happen, you find you’ve wasted considerable time and cash. Especially when ‘isolated’ usually means there are no other options just around the corner.

Image: Tim O’Reilly

However, comparing an average day on the water to one where the fish go bananas is the reason to chase this dream. Those incredible days where everything falls into place, the fish are not only there, but chopping like crazy, and you’re the only angler privy to the spectacle. That’s what keeps us going back over the years or what sparks someone into loving fishing in the first place: the knowledge that you don’t know where and don’t know when, but if you keep trying, eventually that mother load of hungry fish will materialise.

Anglers will make any excuse to chase that dream around!

Image: Tim O’Reilly

So next time you make yourself a fishing plan, keep a few of these factors in mind. Fishing isolated structure can form part of almost any planned fishing day. Even a marlin boat out chasing billfish on the edge of a large canyon is using isolated structure to trap fish, even if that structure can’t be seen or fished and is merely changing the flow of nutrients or prey, upwelling currents or funnelling life.

All the same principles apply to whatever isolated structure you choose to fish.

Go get amongst it. 

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