Apologies for the jargon, but a negative Indian Ocean Dipolar index (-IOD) is really starting to work its magic in south-eastern Australia. If you’re not a weather nerd, a -IOD means warmer-than-normal oceans off north-western Australia, leading to greater evaporation, meaning more atmospheric moisture streaming across the continent for south-eastern weather systems to tap.
If you’ve glazed over reading that sentence, all you need to know is that large parts of western Victoria have never had below average rainfall in a -IOD year – and usually, it means above average rainfall. In climate terms, where variability can crush the efforts of even the world’s most powerful supercomputers, that’s quite an incredible forecasting constant. It’s not that we can’t have above average rainfall without a -IOD (we can, and we do). However it is amazing to me that with all the vagaries of forecasting, we always hit at least average with a -IOD.
My obsession with weather is largely because of how it affects the fishing, and we are now seeing the real time impacts of the -IOD on fishing in western Victoria; and will continue to over the coming months. (The -IOD has and will impact a whole lot of other places too, but looking at western Vic will do for now.)
This is the bleeding obvious result of all that rain. Most on-stream reservoirs are either full and spilling, or rising rapidly.
For example, all lakes in the Coliban system (Upper Coliban, Lauriston and Malmsbury) are spilling. Newlyn and Hepburn have been spilling for weeks, as has West Barwon Dam. Tullaroop is at 56%, a 5% rise in a week. Moorabool is at 70%, versus 55% this time last year. In the Grampians, Wartook is 66% versus 40% last year. In short, the important man-made trout lakes are full or rising steadily.
It’s a similar story with the natural lakes. For example, Deep Lake and Tooliorook are full, a far cry from just a few years ago.
Can you have too much water? For the well-being of lake trout, hardly. In fact for several western Vic lakes, simply the presence of plenty of water is the main driver of healthy trout stocks.
The immediate dividend with rising lakes, is water flooding terrain which revegetated when the level was lower. The result is that all sorts of terrestrial food – worms, beetles, grubs, etc – is flushed out, becoming available to ‘floodwater feeder’ trout. How this benefits actual fishing is nuanced, but if everything lines up, the action can be superb. More about this in future articles.
Aside from what may or may not be immediate flyfishing benefits, water flooding lake shore vegetation sets up all sorts of future opportunities. The habitat provided by flooded grass and plants soon houses thriving populations of baitfish, frogs, stick caddis, nymphs, and lots of other trout food. Meanwhile, the rotting vegetation creates an ideal environment for the chironomid (midge) populations to explode. With a lifecycle of as little as two weeks, it doesn’t take too long for flooded lake margins to provide great midge fishing.
While I’ll take a -IOD event any time I can get it, it’s not without possible downsides. First, really heavy rain can cause flooded inflows to badly discolour the lakes they feed. While the trout don’t mind, for actual fishing, it can make blind searching very difficult. You really need to be able to locate a trout to cast to, to have a decent chance.
Secondly, on a related note, if lake levels rise too fast, all the flushed food can end up metres down and a long way offshore. At best, this pulls the trout out of easy range. At worst, they can end up so full, it’s hard to persuade them to take one more ‘wafer thin’ mouthful and eat your fly.
Thirdly, for a period on lakes which have been below full for a long time, the water can flood up into vegetation that’s so tall and dense, actually fishing in it (and locating the trout) can be a challenge.
Still, none of these issues lasts for long. Once things settle down, the fishing soon ramps up again, and with trout which are bigger and in better condition than before all that rain.