Fishing after the Flood
  |  First Published: April 2010



There’s been a lot of rain around the catchment of many Queensland’s lakes in the past few months, which has caused dam levels to rise. These rises have a big influence on the fish, their movements and their willingness to bite.

Unlike a flooded river or creek, a dammed body of water will not quickly recede. Maintaining this new, higher level has a number of effects over the entire system, all of which change over time. Understanding the principles of what is taking place will help us to more successfully target our quarry when fishing after the flood.

The Big Rain

Drenching rain pounds the hills of the catchment area until the ground can take no more. The water starts to run, first through the grass and dirt, cutting little drains as it trickles downward. In the gullies the draining water meets and starts to flow from one channel to the next. As it travels, the pace increases until it reaches feeder creeks. These many smaller creeks finally join the raging rivers that feed the impoundment. As the floodwater enters the lake body, the stored water slows the flow and the level start to rise.

During the Event

These changes have an immediate impact on the fish. Our freshwater fish were comfortably swimming around at their chosen depth. To remain in that spot requires their bodies to quickly adapt to the increasing water level. It may not sound like a big deal for a fish to stay put – after all it’s wet already. However, like humans, fish suffer from depth changes. The more sudden the change the more effect it can have. In fish, air bladders play a big role in keeping them stable and upright in the water. This is why fish will often go off the bite when a weather change moves through. Atmospheric pressure conditions take a toll on fish even though they are underwater. An adverse change will quickly upset a fishes’ air or swim bladder. Until it has time to adjust, it’s going to be tough to catch.

Fish will only remain at their same location during a rise if their air bladder is comfortably able to adjust. In my experience, the deeper holding fish are the ones more likely to make a move when a dam rises. Fish that were holding close to the bottom will often rise as the dam fills. If they were schooling in 30m of water and the dam was to rise 10m, they are likely to be sitting 10m off the bottom in the same area.

Shallower holding fish seem to have the ability to adjust more quickly. These fish are able to quickly take advantage of rising water levels. They will move into the shallow water in search of food or even into the current of the floodwater.

After the Event

When the water has stopped flowing, consistent fish catching patterns will start to emerge. The fish are able to adjust and will usually continue to feed. Deep fish will relocate to nearby areas and shallow feeding fish will take advantage of the fresh food on offer in the shallows.

The floodwater will usually separate from the old existing dam water with a distinct colour change taking place within a relatively short distance. Even when filthy floodwater that is carrying lots of silt enters the lake, it tends to stay in the upper part of the dam. If the lake level is very low before a big influx arrives, the floodwater will make up the biggest percentage of water. In this situation, the entire dam can be filthy. If the fish are able to cope with many variables like sudden temperature change and gas and chemical imbalance, they should adjust quickly to the new water. It is best if low lakes rise in a number of stages rather than all at once. Unfortunately this isn’t always how it happens.

When dams are inundated with heavy rain, the increasing level can force low-oxygenated water to the surface. This is common in high-temperature conditions and can lead to fish being starved of oxygen. It is believed this phenomenon caused a fish kill in Moogerah Dam, near Boonah in December 2007.

Different fish species will react differently to increased water levels. Deeper fish will feed in a similar manner to the way they did before the rise. The shallower feeding fish are the ones that really take advantage of the new conditions. Over the shallow grassy banks a smorgasbord will be found. Insects, worms and frogs are flushed out with the rain and attract all manner of fish. Predatory fish will come into the freshly covered water and take their share. Small insects and eggs will bring in the smaller fish species like guppies, gudgeon, gar and bony bream. These fish will also attract the larger predators. Life over the freshly flooded banks will be plentiful for the coming weeks.

Using Science
Vegetation Breakdown

The water takes its toll on submerged terrestrial plant life and it starts to die off. As weeds and grasses die, they release gasses into the water. In an environment lacking oxygen, such as below a thermocline, these gasses can be quite nasty. Fish will avoid these low oxygen areas where gasses like hydrogen sulphide, methane and ammonia are produced. In closer to the edges, decaying plant life will reduce the water quality which explains why a month after a huge rise the fishing can be so poor. Finding areas higher in oxygen is the key to finding the best concentrations of active fish.

Go to O²

Fish use their gills to extract oxygen from their watery environment. While their respiratory system is extremely effective at removing available oxygen from water, higher O² levels equate to more active fish. In water carrying a low oxygen content, fish will be less active. It takes energy to move about, hunt and even break down food. To burn energy requires a higher oxygen intake.

In some situations it is almost impossible to find the right piece of water after a significant dam rise. When fish are tight lipped, presentation becomes critical. Placing the lure right in front of them can be the only way to get a response. Searching for the highest level of oxygen is often the key.

Even after plants start to decay, the best concentrations of oxygen rich water are right in the shallows. Here, oxygen content is highest due to the contact of the water with the atmosphere. Mix some wind into the equation and you start to see even more oxygen blended into the water.

Wind plays a major role in selecting a fishing location. Surface layers of water are pushed around by the wind concentrating that particular water in one area. On large open lakes, poor quality water can be quickly enriched with O² by the rolling action of the water. The windiest spot may not always be the most comfortable but in tough conditions, it is the most productive.

Biological Oxygen Demand

While plant life may be dying, the first thing to flourish after a rise is the algae. Such blooms can be unnoticeable and have consequences that anglers rarely consider. Like all plants, during the day algae produces plenty of oxygen as a result of photosynthesis. Without light, the algae go through cellular respiration, which uses up oxygen and produces carbon dioxide.

This process may help explain why the fishing is sometimes better in the afternoon than the morning. After a full day in the sun, algae can boost the O² content in the water, making conditions more desirable for fish to feed. This course of action may help explain why barramundi in Lake Monduran’s algae rich green waters often bite best in the afternoon.

The Food Chain

As water runs into a lake, it brings with it sediment and nutrients. It can also carry less desirable chemicals like pesticides, herbicides and fertilizers. The rich nutrients promote the growth of algae and plankton. These minute organisms are the building blocks for a healthy system. Smaller fish like bony bream and crustaceans like redclaw and shrimp thrive on the plankton and the extra food promotes their numbers. More baitfish in a lake presents the predators with extra food and the fish are healthier as a result. Fooling a fish with a lure may be tougher when a lake is swarming with bait.

This process all takes place in the months that follow a rise in water level. The fish benefit as a result but it may take some time to see the positive effects. Once everything stabilises, expect the action to be red hot.

Fishing

As anglers we have to cope with whatever is thrown at us. We don’t always have the luxury of going fishing when and where the action is red hot. After a lake rises in level, the action that follows can be hot and cold.

Lure Selection

Fish found in dirtier water after a flood might call for a special lure. Fish feed using all of their instincts. When sight is reduced senses like feel, hearing, smell and taste take over.

Changing lure colours to ones which stand out in discoloured water will help fish see your presentation. Fluorescent colours and white stand out well in dirty water. Chrome gold is also a great option as the flash it gives off in the sun reflects a long way, even in dirty water.

Fish are able to feel movement in the water around them through their lateral line. Lures that create more vibration are therefore more likely to get noticed in dirty water. The lateral line is visible as a line running lengthwise down the side of the fish.

Fish also have ears, which work closely together with the lateral line to sense noise, which is in essence a form of vibration. The ears are an internal organ and noise vibrations can easily transmit through the water and pass into the body of the fish to the ears. Noisy lures that rattle can therefore be a good option when visibility is poor.

A fish has nostrils that are capable of detecting chemicals. The ability to detect chemicals (chemoreception) is very developed in some species. Adding catch scents to lures can help to fool fish into eating your lure. Scents mask unnatural odours like fuel and sunscreen. Catch scents also add taste to an artificial presentation. Fish have taste sensors on their tongues, lips and all over their mouths. In a dirty water situation, adding scent to appeal to a fish’s smell and taste can only help put the odds in your favour. Adding scents makes sense.

There are several ways to make our lure stand out in dirty water. The trick is to select a presentation that stands out enough to appeal to the fish without scaring them away. If you go too big and noisy the fish will certainly know the lure is in their territory and they’ll be heading in the opposite direction.

Navigation

Flooding rivers bring with them plenty of hazards. Floating branches and debris can be found anywhere in the lake – usually where you least expect it. It pays to keep a close eye on the water ahead of you in case there is a big log in your path. Slowing down, especially on dark, might be necessary to avoid collisions.

Targeting Freshwater Species after Water Levels Rise

Despite many of our freshwater natives sharing the same waterways, they can react differently to a rise in water level. Flooded lakes inundate massive areas and quickly increase the surface area for exploration. One might think the fish would be tougher to catch with so much more water to explore however, when water flows into a lake it can actually help to relocate the fish into more specific areas.

Unfortunately I don’t get to fish as many rising or recently risen lakes as I’d like to. I live near Toowoomba where we have been on strict water restrictions due to low lake levels for what seems like a decade. Therefore I get excited every time I hear a lake has had water run into it. Fish will continue to do their own thing but there are some patterns that have taken place over the years. Golden perch, bass and barramundi are three of the most sought after freshwater species in Queensland. Let’s take a look at how these three different species can react at different stages when a lake rises.

Golden Perch
During the Rise

As water runs into the lake, many golden perch will move upstream into the running water. There are many influencing factors and if water conditions don’t suit, the goldens may stay away from the fresh water altogether. It is still certainly worth investigating the running water especially in smaller, narrow feeder creeks. This migration could be based on the breeding instincts of the golden perch. Clearer running water is certainly more fishable as lures will quickly disappear in dirty turbulent water.

Maroon Dam fished extremely well for golden perch several years ago while the lake was rising. The water running in was quite clear and the goldens were concentrated in a massive school in the running water.

Back eddies or sections where the current is broken are likely to hold the most fish. The fish will be facing into the current. When presenting the lure keep this in mind and try to run it in front of the fish.

Running water isn’t always the best option as it may be too unsafe or dirty to be bothered with. In this situation, try targeting the freshly flooded banks. These areas will continue to fish well over the coming weeks.

After the Rise

The flooded banks provide plenty of food for foraging and hunting fish. After the rain beetles, grasshoppers, worms and other terrestrial creatures are washed into the water. This creates an instant food source and golden perch will be quick to move in and take advantage of the easy meal. Years ago, I even witnessed golden perch taking surface lures. The fish obviously thought they were eating some kind of insect.

The smorgasbord of fresh tucker also attracts plenty of smaller fish. These fish are able to dine around all the freshly flooded vegetation. Predatory fish like golden perch won’t pass up an opportunity to gorge themselves. The smaller fish feeding there will soon become food for something bigger.

Often the best banks to fish are those around the camping and boat ramp areas. These spots will usually have gentle sloping banks that have been mowed often enough to keep the grass short. This shorter grass makes lure and bait presentation much easier.

The time fish spend feeding in the shallow water will depend on the water quality. If the water promotes fresh weed or grass growth, this can be enough to counteract the dying weed. In this instance the fish will remain in the area for some time. After their initial indulgence, they may not be as hungry but the shallows will still be one of the best spots to fish.

When the weed dies it may be time to look for more suitable water. The fish will either head to deeper water or look for the shallows holding the most oxygen.

Lure Selection Deep Water

In running water a spinnerbait is an excellent option. These lures can explore the snags and continue to work well even in the stronger current. Willow leaf blades will work better in faster water as their slender profile is less affected by the current. Opt for gold blades over silver ones especially when the water is discoloured. Gold will send out a more noticeable flash.

Hard-bodied lures can be thrown off balance in fast moving water when they are worked across the current, but are quite effective when trolled directly into or with the flow. Trolling shallow divers in the running water is a great way to explore the area. At times the fish will pounce on shallow running offerings. Lures like the Halco Combat that run between two and four metres deep are perfect. Experiment with colours. Brighter coloured lures or chrome gold will be suited to dirtier water while darker hues or black will be perfect if the water is clear.

Lure Selection Shallow Water

When casting to actively feeding golden perch in the shallows, it’s hard to beat a spinnerbait or lipless crankbait. These lures create plenty of vibration and the speed can be controlled or weight selected to suit the depth of the water being fished. Both lures are quite effective when it comes to fishing flooded vegetation. The lipless crank can be ripped out when it fouls while the spinnerbait tends to glide straight through. Gold lures are a great choice for chasing golden perch. Keep this in mind when selecting spinnerbaits as the flash of a gold blade makes me more confident.

Shallow water trolling is another good option. Goldens will take trolled lures in water between 2-4m deep. Using an electric motor to stealthily move along will increase the chances of success. It is amazing how responsive the fish can be in shallow water if you are sneaky. Over the years, I have had the best success on gold or black lures.

Australian Bass
During the Rise

It takes bass longer to react to rising water levels than other species. Fish holding in deep water will usually suspend in the water column in the same area. These suspended fish can be targeted using everyday techniques. Lures like blade baits, Mask Vib Jackalls and soft plastics should get a response if the fish are willing. Sometimes extra speed in the retrieve will draw a reaction strike from these suspended fish.

Bass holding in shallower water are fastest to react to rising water levels. These fish will move up onto the freshly covered ground where they will hunt and forage. At this stage bass are quite willing to take surface presentations. They will spend much of their time swimming around focused on the surface for insects and small fish. Even lakes that are not known for their surface fishing can produce bass on topwater lures after a big deluge.

The bass hunting the shallows will take many styles of lure. They will be opportunistic in their feeding and take whatever comes along. Spinnerbaits and lipless crankbaits work very well simply because they are able to explore so much water.

After the Rise

Often after a serious rise, the bass in the deep water will shut down and take some time to adjust. In lakes like Somerset where the majority of bass hold in deep water this can result in poor fishing for several months until the fish adapt. When conditions improve the feeding frenzy that follows is often worth the wait.

The fish found in the shallower water will usually remain quite active for at least a month after the rise. When there has been a big rise, the action will slow down faster as the submerged plants die off. If the rise has been of less than two vertical metres, the shallow water action can continue for many months.

Some of the best bass fishing I have ever experienced was after a small rise. Thick weed beds had been covered by just under a metre of water. Casting beetle spins over the submerged weed and cranking them back flat out drew some smashing strikes. The fish were suicidal.

When a lake experiences a small rise like this, there is no reason for the water to reduce in quality. It can actually promote weed growth that will improve fish habitat. The initial feed splurge over the first few weeks will be the best but the action should continue.

Lure Selection for Shallow Water

Surface luring has to be the most exciting form of fishing. Watching a bass explode on top as it engulfs a topwater lure has great visual appeal. When choosing topwater lures it pays to have a good selection. Fizzers, stick baits and poppers have different actions and a particular style may be favoured on the day. Bass poppers should be between 50mm and 100mm long.

Bass holding in the shallows can effectively be chased using search baits. Spinnerbaits, beetle spins and lipless cranks like the TN60 Jackall can be fished quickly in search of fish. These baits will draw reaction strikes as they are buzzed past the fish. Once fish are located other offerings like suspending jerkbaits or deeper diving crankbaits can be used.

Water colour will dictate choices in colour and sonics. Rattling bright lures are suited to dirty water conditions while silent natural or even ghost colours are best used in clear water.

Barramundi
During the Rise

During the rise barra can feel the urge to move upstream or downstream if water is flowing over the spillway. As water runs into the lake, barra will often move into the flow. Even in dirty conditions barra are still viable targets. One only has to look at the colour of the water fished up north during the runoff to see they are still capable of finding the lure. Both poppers and plastics can be tossed across the current in search of fish. The best running water to fish will be found in the small feeder creeks and gullies rather than the main river. These narrow sections confine the barra to a smaller area making them easier to target.

If the dam runs over the spillway, it is likely the barra will instinctively follow the flow. Fish will be lost from the impoundment but, if they survive the ride, take residence in the system below the dam wall. In such a situation, the current created by the water moving through the whole dam will encourage a big percentage of the fish to head for the dam wall.

After the rise

After the rise has settled the barra will be feeding in the shallow water. It is amazing how such big fish can hide in skinny water barely deep enough to cover their backs. Shallow tapering banks will hold most of the active fish. Concentrating on working lures around the prominent points gives anglers a good chance of scoring fish. This requires patience as it can take a while for barra to move through or turn on. Points can be fished by anchoring the boat a cast length away. The depth the boat is positioned in doesn’t seem critical for this type of fishing. Anglers rely on the fact that to get from point “A” to point ”B” the fish will at some stage need to move around the protruding piece of land. At least one angler should be fishing all the time. Bad luck could see the fish pass through while nobody is fishing.

Electric motoring along the banks is a good way to cover plenty of ground. Ensure lures are landed right up close to the water’s edge. It pays to work the lure all the way back to the boat until you discover where the fish are holding. Sometimes they will be right up in the shallows and on other occasions, they may favour deeper water of around 3 metres.

When the fishing is tough look for the most oxygenated water you can find. Barra are big fish and big fish require plenty of oxygen to go on a feeding spree. Windblown banks are always a good option even if wave action has dirtied the water right up. This aerated water is often the most suitable place to target barra after a dam rises. On big open lakes like Awoonga, a heavy anchor with plenty of chain will be necessary to hold the boat in the strong wind and wave action.

Lure selection

In the running water, fizzers are a great option. The spinning blades that chop the water let the barra know the lure is in the area. Soft plastics can also work well and are able to work the water over quickly.

When moving to the flooded banks after the rise, both shallow diving hard bodied lures and soft plastics work well. Soft plastics are a great lure to locate fish. The fish must have an instant reaction to the presentation or it will miss the opportunity. Light lures are usually the best for this style of fishing. Try using Slick Rig Pro Range or 5” Hollowbellies rigged on 3/8oz jigheads.

Hard-bodies can be fished slower to keep the lure right in their face. Hard-bodies are ideal when you know there are fish in the area as they simply don’t cover anywhere near as much area as a soft plastic. Shallow running lures like the B52 and 120 Halco Laser Pro are ideal for this shallow water. They can be twitched on the surface, ripped down and then allowed to float back up or weighted to suspend by adding heavier hooks or stick on weights.

Rising water levels in lakes is something we don’t experience often enough to make totally accurate conclusions. Sometimes the fishing we experience can be red hot while on other occasions it’s near impossible to get a bite. Understanding what happens during and after the rise and fish movements based on past experiences can help us to better our chances. An important thing to keep in mind is when the fishing is tough; the healthiest water will produce the best action. I wish you luck fishing after the flood.

Facts

Dam Level Rises

Many of the lakes in Queensland have had significant increases in water levels over the past few months. This graph shows the levels from January through to the beginning of March. As I write, a monsoonal low that started in the Gulf of Carpentaria has circled through the centre of the state and then moved across the south east Queensland coast. This rain may have delivered even more water to some of the lakes.

Water BodyJanuaryMarchChange

Somerset82%100%18%
Hinze88%100%12%
Maroon80%88%8%
Moogerah43%60%17%
MacDonald78%100%22%
Borumba89%100%11%
Cania5%27%22%
Wuruma2%6%4%
Monduran 25%54%29%
Awoonga48%81%33%
Callide6%26%20%
Teemburra86%100%14%
Kinchant55%100%45%
Proserpine69%84%15%
Tinaroo58%79%21%

Reads: 5260





Current Advertisers

Victoria Fishing Monthly
Queensland Fishing Monthly
New South Wales Fishing Monthly

Fishing Monthly Magazines On Instagram

Latest Articles

Digital Editions

Read Digital Editions

Current Magazine - Editorial Content

Victoria Fishing Monthly
Queensland Fishing Monthly
New South Wales Fishing Monthly