A heat wave all across central Europa has rendered many troutstreams and creeks unfishable. While some shallow stillwaters were on the edge of an ecological disaster, deeper reservoirs provided a safe haven for fish to survive both heat and drought. For us fly anglers, it’s crucial to practice self limitation for the good of the fish. Even proper catch and release practices might not help if the water is simply too warm and the level of oxygen dissolved in it, too low. Plus, there’s nothing wrong with a good cold pint at the pub, when it’s too hot for fishing… (read: http://www.fieldandstream.com/blogs/flytalk/2013/07/do-you-stop-fishing-trout-when-water-temperatures-become-too-hot)
Not only, but especially in warm circumstances, reservoirs can be the last resort. Finding fish in these bodies of water is crucial and I narrow my limiting factors down to benevolent temperatures. The dusk and dawn fishery can be immensely rewarding, as trout are actively feeding in higher water columns – being out early has never been as true as in these days…The early bird…well, you know the drill.
The thermocline is the zone of greatest temperature change and our best shot for sluggish summer fish, especially in bright daytime conditions. Most of the heat is absorbed in the upper water column. During summer, warm water with a lesser density will float on top of colder water at the bottom of the lake, the separating layer in between is the thermocline. Since there is less and less oxygen below the thermocline, trout and other fish, usually prefer to hang around in this hot zone, if the surface water get’s too hot. The exact depth can vary greatly from water to water and also day by day.
If multi-fly rigs are allowed, a classic Diawl Bach/Buzzer rig will do just fine, locating active fish in certain depths. On the other hand, summertime also means a variety and multitude of fry-fish – the perfect snack-size food source for bigger critters. Once the fish are located in a certain water depth, I like to work this water column with both lures and boobies – especially if the water is stained or in the midst of a blue green algae bloom. If the latter occurs, bare in mind, that only the top water layer is effected and although the visibility appears to be slim to none, it’s still clear beneath and perfectly fishable beneath.
A heavy lure with two booby droppers has proven to be deadly effective under these circumstances – it’s all about commotion. Crucial for a booby rig are the pauses in between the figure of 8 retrieves. Pay close attention to the tip of your line and your rod, more often then not, they will strike exactly in this phase of the retrieve.