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Sunrise and sunset
When the days are warm, especially with temperatures over 25 degrees in the shade, trout shorten their periods of activity. Trout are not particularly fond of warm waters for feeding.
On the other hand, at sunrise and sunset, a period that becomes shorter as summer approaches, fish move to feed. The air temperature is cooler, as is the water temperature. Trout are generally to be found in very little water, posted in the current, waiting for prey to pass within reach. Low light levels make it easier for us to lure fish that rely mainly on noise and vibration to hunt.
The sun at its zenith
Unlike sunrise and sunset, the zenith hour is not cool and conducive to trout movement. However, if you have a good pair of polarized glasses, you can actively search for fish along the river. Fish often stick to the bottom, in weak currents and in the shade. Using cunning, stealth and small lures, you can catch wary fish. You'll have to use fine line and be very precise with your casts to fool even the biggest fish.
When the sun is at its zenith, you'll also be able to spot which holes and currents have the most fish or the biggest individual. If, despite your best efforts, the fish aren't biting, you'll have a good indication of where to target for your evening strike.
Preserving fish
Summer temperatures are a great danger for trout, especially large ones. Bear in mind that under no circumstances should a trout leave the coolness of the river water. A few seconds is all it takes to take a nice photo before quickly releasing the fish. Also, avoid placing the fish on a stone or any bank exposed to the sun, which could burn the skin of an already fragile trout.
Use a landing net as much as possible, with rubber mesh to keep the fish facing the current while you try to unhook it. Wet your hands properly before grabbing it and always stay above the water when you want to take a photo. A fall to the ground is fatal for a trout already exhausted from the fight. Note that a trout can die from the consequences of too long a fight, 2 to 8 hours after capture, as a result of lactic acid build-up.
