By now we’ve got some inkling about the complex relationships existing between the elements and fish activity levels. The sky and whether fish are moving, biting or sitting out a bad spell. Weather can be in your face or fickle enough to still flummox the best forecasters – and anglers. Wind and rain are tangible enough but the real tricky stuff is to do with the barometer and why fish bite as a storm is about to hit.
The diverse nature of Australia’s rivers and lakes – alpine to outback – along with fish needs that are just as far removed, means that there’s no single set of weather conditions that applies across the land. The still blue skies of conditions beautiful in Victoria means bitchy winds along the Queensland’s coast and hinterland. When it comes to keeping score, Victoria has the most sunny days.
Causes? Weather patterns that have prevailed since we broke away from Gondwanaland. High pressure systems drift west to east across continental Australia. Their centres vary in latitude, mostly ranging from The Great Australian Bight/Bass Strait north to Riverina, but sometimes higher. From the Grape Belt to the Granite Belt, those systems bring on the still and warmish 1020+ hp days - so good for Murray cod. However their impact further north is frustratingly blustery. Wind from the east, fish bite least – an oft recited homily on the Brisbane periphery bass lakes.
Wind has a bitchy influence on the gel spun lines used by the majority of serious lure fishers these days. Trees around the flight paths of cast lures can add up to a trying day.
On the positive side, winds can kick-start a bite. Their ruffling effect oxygenates and cools the surface layer and trout respond by rising in the water column. Blustery conditions dislodge insects from bank side vegetation and cause crash landings. Those victims are often funnelled along what’s known in trout-talk as wind or feeding lanes. They can be easily identified by the changed surface tapestry.
Windward shorelines take on a special significance once a blow becomes a few hours old; the exposed fringes become a long larder. Plankton layers, caught up in a surface rollover and wind driven, end up dispersed along a windy lake margin, especially bays that have a pronounced apex. That presence attracts baitfish and kick starts feeding activity. Bigger predators become activated, shielded by roiled waters.
A Mild Winter
Mild-mannered Gordon Winter was the first to twig to links between a rising and high barometer and a cod bite. His early fishing life was spent flyfishing for trout but as, increasingly, his flies were snaffled by Murray cod, silver and Macquarie perch – there were no goldens above Burrinjuck then – his attentions switched to natives and he went on to be one of the most successful casting anglers ever to tie on a cod lure.
Gordon had an intimate understanding of cod along with boundless patience. He knew where they lived and based his
approach on the simple premise that a time bomb ticked away in their pea sized brain. An intruding lure lit the fuse. He’d draw his way through a few pipeloads of Erinmore while delivering cast after cast. His retrieves were painfully slow. The best ones ended in a puff of smoke that’d work in an Apache movie. The bent rod said the rest.
The Winter theory was that a barometer rising through 1020hp
was a good time for the lawnmower to break down. Then and now, the atmospheric stability accompanying those highs offers the best chance of connecting with a cod around Canberra. And for that matter, any water west of the Great Dividing Range.
The Pressure’s On
There are a number of theories on the connection between a rising and stable barometer and increased native fish activity. The most widespread seems to be the impact of high pressure systems on fish swim bladders. Nah, that one won’t hold water, let alone anything else. The pressure difference contained in a mere foot of the water column is that between a balmy afternoon and a hurricane.
A more likely explanation is that a weightier atmosphere speeds up the oxygenation process. Surface waters take in more oxygen faster. And carbon dioxide. Those gasses are essential in the life cycles of micro organisms. In this minute universe, plankton needs oxygen and feeds on algae. Like all plant matter, algal growths are CO2 dependant. Sunlight is another critical ingredient in their existence. The clear skies that go with high pressure systems sees a light sensitive plankton layer (often mistaken for a thermocline in eutrophic lakes) rising into the surface layer to partake of the sun. That same atmosphere accelerates cell division amongst algae where the light is strongest. The collective effect is a dinner bell. Forage species like bony bream – found from the Murray river through the lakes of the bass and barra belts – are firmly omnivorous. Such activity isn’t lost on overt fish eating predators. Murray cod, bass, golden perch and barramundi
are all instinctively tuned to take advantage of the opportunities that happen when masses of baitfish are pre-occupied feeding.
Calm Before The Storm
Most blokes who’s fished a bit can relate to fish going mad just before a storm hits. One that sticks in my mind happened with Rodney Cook at Glen Lyon dam. We hadn’t done much good and were a couple of miles from the ramp when I noticed the black thunderheads moving in from the nor’ west. We started to head back but the portable outboard and plastic boat wasn’t a distance eater. We caught five cod in half an hour. Two were kept and delivered to Dr. Stuart Rowland and then offsider, Frank Prokop, at the Grafton Fisheries Research Station. The twenty pounder was aged at rising four years and a smaller fish at three.
The storm scenario also holds more thin ice than solid ground. Fact: impending electrical storms lower the light intensity. Fact: fish vision does not adjust to rapidly changing light; not like ours. Aquarium fish that know their way around a tank go colliding with the glass when lights are turned on in a darkened room. Predators adjust quicker to fading light than baitfish. Barramundi have an extraordinary grey scale visual range which is why lake fish have a bite window around dusk. Cod and bass are naturally nocturnal and respond to opportunities lowered light presents.
Besides perpetuating the lament “wet arse and no fish” rain doesn’t seem to have any immediate effect on the strike rate one way or another. Enough drops from the heavens can produce a golf green surface smoothness.
More often than not however, accompanying squalls have the opposite effect. If associated with a storm cell, an open boat is not the place to be. First generation graphite rods carried lightning conductor warnings but since that was bad for business the stickers were phased out. The next fisho to get himself fried through a cavalier attitude to thunderstorms won’t be the first.
Sun and Shade
Murray cod, bass and yellowbelly all share that fish aversion to strong light. During bright and still days, cod are at their cantankerous best between midday and two-ish. That time frame sees the sun at a zenith. Sunlight penetration is at a maximum and shadows are minimised. Having their space reduced heightens aggression levels. An associate trigger is the coinciding peak in the day’s water temperatures. Save those long and leisurely lunches for the dull days.
Cloudy days increase the possibility of fish taking advantage of the less intense light and moving about. Moving fish tend to be hungry fish and that increases the odds of angler contact.
Waters high and Low
Rising water levels are a fish turn-on. However there’s a world of difference between a fresh and a flood. It’s as if someone hit a switch the way river fish bite immediately prior to, and as a rise from upstream rains arrive. High rivers are a migration cue. The illegal wire traps of graziers with river frontage – some needing tractors to haul out – were always positioned with the entrance funnel facing downstream. The direction taken by migrating natives is always upstream.
Rising water levels trigger feeding activity for lake fish. As new ground becomes inundated, various terrestrials become mixed amongst those fringe waters. A veritable smorgasbord that brings yellowbelly and silver perch into waters (provided they are coloured) less than a metre deep. Big rises change the ambush potential of cod cover. Greenfish may be forced to re-locate. It’s looking ahead to reconnoitre exposed rocky points, snag complexes and sections of steep rocky bank.
Falling water levels are a turnoff in rivers. But provided the drop is inches per day and not feet, confidence levels needn’t fall. In a contradiction of sorts, a discharging lake can be an absolute bonus. It’s a situation brought about by the strategic location of dam walls. And gravity. Dam builders seek out strategic sites in river gorges and gaps between hills that allow them to back up a maximum mass of water with a minimum amount of locally quarried rock-fill and concrete.
When a lake is discharging, a current sets up in the main basin. Gravity pushes water along the former river bed. The nuances of this movement is beyond our monitoring capacity, but it’s there and fish know. An acceleration – if that’s the word for a glacier pace speed – takes place through funnel effect where the main basin joins narrows across which the wall is built. In the relatively shallow Queensland coastal lakes where both are stocked, bass and yellowbelly locate this moving water and congregate on, over and about bottom features that have a deflecting impact.
The Eastern Fall
The roots of this little gem are firmly anchored in agronomy, but apply to lakes in the same profound way. Eastern facing slopes get the first of the morning sun and the best of prevailing rains. Lakes located in coastal hinterlands, cradled in the Great Dividing Range and those on the western slopes all receive the bulk of their rain from clouds travelling from the east. In the buy and sell arena of rural properties, those with predominantly easterly aspect slopes fetch far bigger dollars than those with a westerly fall. In a nutshell, the easterly fall country is richer, the soils are more fertile, things grow better. That farming fact of life isn’t lost on insects and other water edge terrestrials that form much of the lake food chain. Prevailing easterly aspect winds are working for the thinking fisho by accumulating plankton, drowned insects and other items in the food chain along windward shorelines. The message is obvious; east is east and west is west.
Harro at Large 2020
Rod Harrison has caught the world’s great salt and freshwater fish on a fly rod.