Just a few weeks ago I was focussed on finding cooler water to fish. As summer lingered into early March, tailwaters and the upper reaches of the natural streams were the places to be. Early mornings and right on dark proved the best times to find aquatic insects like caddis, mayfly spinners and mayfly duns on the water attracting rises – the middle part of the day appeared to be simply too hot for anything much except grasshoppers.
Seeking cool water midsummer on a shady upper Murray tributary. It would be very cold in that valley now.
But now things have swung back the other way. Overnight minimums in single figures are the new norm through most of our trout districts, and at higher elevations, frost and even a dusting of snow are possible for the coming week. This happens every year, but it always takes me a little by surprise that my buff is suddenly more valuable for keeping my ears warm than keeping off the sun.
Early May snow in the upper Cobungra valley. Once snow arrives water temps really start to plummet and the catchments with snow are best avoided.
From a trout fishing viewpoint, the coming month is one of the highlights of my year – although I need to recalibrate my thinking. Now warmth is something to be welcomed and cold is the hazard. The 11 am til 5 pm period is prime time. While water temperatures are now in the supremely comfortable range for trout most of the day, I like the thermometer to be trending up if anything rather than down. Trout are cold-blooded and as long as the water temperature is within their comfort range (and it always is at this time of year) I would prefer their metabolisms to be going faster, not slowing down.
Late morning until a bit before sunset also tends to coincide with the day’s highest air temperatures and therefore the greatest insect activity. As trout ‘hunger’ can loosely be described as corresponding to the availability of food, this is a nice double: trout with a higher metabolic rate needing more fuel, and more of it available to spur them on.
This big Millbrook rainbow was feeding hard on duns in 15 C water at 2 pm Monday afternoon.
For the number crunchers, here are a few figures of autumn interest. The coldest water I’ve ever caught a trout on the dry fly? 3 C (Victoria River in May). Coldest water I’ve consistently caught trout on a dry fly? 6.7 C (Moonbah River last year, late April). Water temperature when I tend to find feeding trout vacating the fast water for the slower pools and glides? Less than 10 C. Air temperature that kills off most of the hoppers? A few nights at 0 C or below will usually do it. When it’s really cold, the water temperature on lake or stream that I’ll move around to locate (if possible)? Greater than 6 C.
Borderline conditions on the Bundarra: May and after sunset, though we still caught a few fish.
Of course the ‘fish when you can, where you can’ philosophy should continue to apply through autumn just as at any other time of year. The outliers in trout world mean there are usually some fish that will be catchable (like the Victoria River brown above) even when the temperature equation is against you.
