THE LINK BETWEEN TROUT BEHAVIOUR AND WATER TEMPERATURE
We are often told to stop thinking like an angler and start thinking like a fish to maximise our catch rates. But you can’t really think like a fish until you truly understand how external factors affect their behaviour.
This is apparent with most species of true trout and is true for one of the most common and popular angling fish in Australia, Brown Trout. You can fish the same tackle, in the same way, at the same time of day, in the same location, and get completely different results. One factor that is often overlooked is water temperature. It is critical to the fish’s survival and has a profound impact on their feeding habits. Here is some of the science behind the effect water temperature has on fish behaviour and how you can use it to your advantage when chasing them.
In warmer water, anything over 22 degrees, oxygen levels drop. Trout tend then become lethargic and fixated on finding shaded spots with enough oxygen to continue breathing, they won’t even take a fly that drops onto their nose. Similarly, in cooler water, under 10 degrees, the fish’s metabolic rate plummets. This means they require less food to survive and will stop taking flies.
The optimal temperatures for Rainbow Trout are between 10 and 22 degrees. Brown Trout are slightly more accustomed to colder water, managing to thrive in water between 4 and 19 degrees.
APPLYING THIS TO YOUR SEARCH FOR TROUT
In the summer months, when temperatures are at their peak, look for water sources with cooler temperatures. This means looking for shade, in flowing springs, or elevation. Gorges and streams with dense foliage coverage are great sources of feeding fish in summer.
During a really cold snap in the winter, the fish will find a place and group together, becoming almost dormant and with no inclination to feed. If you are determined to get something when the water temperatures are cold, you will have to find them because you can be sure they won’t come to you. Once you’ve found them, the only way to take them is by dropping flies right on their noses. They don’t need to eat, so you need to tempt them with a food opportunity so easy they have to give in to the temptation.
In the spring, target shallower water which will warm up faster and get to optimal feeding temperature quicker.
Some of the best times to target Brown Trout are during periods of temperature fluctuation. It doesn’t matter if the water temperature is rising or falling, the mere fact that the temperature is changing is often enough to trigger a feeding frenzy and bring fish onto the hook.
CHANGING TARGET SPECIES
Alternatively, you can use warmer climes to change target species. Perch and Australian Bass both handle warmer waters better than Brown Trout and are better at competing for food when the oxygen levels dip. You can use the hot summer months to change your target species and return to Brown Trout when water temperatures fall.
While this information is useful as a general guideline, I have to add the caveat that Brown Trout is one of Australia’s most unpredictable species, fun-fishing species. Temperatures and conditions that I would have expected to deliver plenty of Brown Trout have sometimes seriously disappointed, and some days when I have had low hopes and minimal expectations, I have returned home with a full bag. Water temperature is something to consider and a good understanding of its effect on your target trout species will give you a competitive edge but expect the unexpected.
Have you got anything to add to this article? Share your experience in the comments section.