Fly Fishing for Trout in Hot Conditions

As temperatures begin to rise, catching Trout can be a bit of a challenge. As the water temperature increases, the amount of oxygen decreases, and Trout can stop feeding until the water cools down again. A common scenario is when you arrive at your chosen Stillwater or reservoir, conditions are very bright, it's very warm, and there is a flat calm with just one or two rises. So how do you adapt? What tactics should you adopt?

It's important to know how heat affects the water temperature in the first place. The sun heats the surface layer but deeper down, the water is cooler and this is where you will find most Trout, in the cooler, significantly more oxygen-rich water. However, what can make matters more confusing is that wind can mix things up and push the warmer layer to one end of the lake. When this happens, fish will keep on the move to stay cool.

So you might be asking if it's too hot, is it worth fishing at all? Yes, but it can be a bit more challenging. The best time would be early morning and late evening when things are a bit cooler. During this time, the fish will have enough energy to move around and feed. It is very common for fish to feed aggressively at this time and sometimes the water looks as if it is 'boiling' due to the number of rises. However, in the heat of the day, it is the deeper, colder water you want to target. If you are fishing a reservoir, look for dam walls or where the water slopes away into deeper holes or channels. Here you will find fish congregating.

Maybe I Should Be Moving to Deeper Water?
Since Trout favour oxygenated water, another place to target during warm conditions is a stream or spring inlet. These not only carry insects but also bring in cooler, oxygenated water, and it is around these areas that fish are more comfortable. Another area to consider is near the 'boils' or aerators. In some larger reservoirs, aerators pump massive amounts of oxygen into the water producing oxygen bubbles. It is in these areas that fish can congregate in large numbers and are a top target for many fly anglers.

Regarding what fly lines to use in hot conditions, if, for example, you have chosen to fish a reservoir, your first port of call should be the dam wall or deepest part of the lake. As discussed, the fish will lie deeper in the cooler, oxygen-rich water, so using a fast sinking line offers a significant advantage. In contrast, if you were to use a floating line, it is very difficult to reach the target feeding zone if the depth is significant. The floating line wants to sit on the surface, so the only way to get to the target depth, if reachable, is using a longer leader and a heavy point fly. You can catch fish on this setup, but waiting for the fly to sink takes longer due to the floating line's resistance. Ideally, you want to be using a fast sinking line.

Fast Sinking Line Techniques
A sinking fly line's sink rate is categorised by the number of seconds it takes to sink 1inch. So for example, if the fly line is a Di3, the sink rate of the fly line is 3 inches per second. This is called 'fly line density.' So what you need to think about is it will take a Di3 longer to reach the bottom of the lake than a Di7. A Di7 sinks at seven inches per second so will reach the depths a lot quicker. A floating line obviously doesn't sink, and an intermediate sinks around 1-1.5 inches per second.

Fly Line Sink Rates
When you need to fish deeper, a Di7 or Di8 with a team of buzzers fished using the washing line technique, with a buoyant fly on the point such as a booby or blob is a very popular method. (please check the fishery rules regarding the use of the booby). Change the patterns and sizes regularly until you find out what works. Pay attention to the colours in the fly which the fish are taking most. This can eliminate a lot of guesswork. If buzzers are not doing the trick, try crunchers, Diawl Bachs or something unusual that will spark their interest. Also, try patterns with a bit of sparkle and attraction such as holographic tinsel, mirage, or something with a fluorescent hot-spot.

Cruncher Selection
One of the most important aspects of fishing a fast sinking fly line in the deep water is paying attention to how long the line is sinking. As you cast out, and the line hits the water, start to count in your head how many seconds the line is sinking. If after 10 seconds you get a confident pull or better still, a fish, then you know that fish are roughly 10 seconds down. If you want to do the maths, 7x10 = 70 inches or 5.8ft for every 10 seconds.

Fishing with a Fast Sinking Line
When you are retrieving your flies using the fast sinking line technique, remember the line is continually sinking so the retrieve should be a bit faster or fish a shorter line. If the fish are taking the top dropper this is an indication that the fish are feeding deeper down because the top dropper is closer to the fly line itself. By staying observant to these subtleties, you can make better choices. Another point to consider is varying the retrieve. Try a couple of fast pulls, a long strip, then a couple of twitches. By using this method you are simulating a variety of natural fly movements, such as an emerging buzzer.

Airflo Forty Plus Di7

Greys Platinum Extreme Fly Line
To fish with a fast sinking line, you need a rod that takes a #7/8 line. The most popular, and reasonably priced setup, is a Greys GR40 4 Piece 10ft #8 Fly Rod matched with either a Greys Platinum Extreme Sink T7 WF8 or an Airflo Forty Plus Di7 Fast Sinking Line. Both lines balance very nicely with the Greys rod and are perfect for the fast sinking method.

Greys GR40 Fly Rod

Regarding leaders for fast sinking lines, if you are using the washing line technique, a leader length of at least 15ft is not unusual. And because you are using a heavier fly line and heavier flies, you are looking at 8lb to 10lb fluorocarbon tippet material. One of the most popular is Fulling Mill Masterclass Fluorocarbon Leader which is highly supple but dense, giving it the quickest sink rate out there. Because you are fishing deep, cooler, oxygenated water where fish congregate, it is not uncommon to get double hook-ups. So using a stronger leader with well-tied droppers is essential.

Fulling Mill Masterclass Fluorocarbon
If you are expanding your selection of fly lines to include a fast sinker, which we highly recommend, then it is a good idea to have a fly reel system that will allow you to swap fly lines to suit the conditions. One of the most popular fly reels is the Greys QRS Cassette Fly Reel. With just the flick of a switch, you can quickly change from floating line to fast sinking line. The QRS comes with 4 spare cassettes for different fly lines and is perfect for the improving fly angler who wants to fish at different depths and adapt to the conditions at hand.

Greys QRS Cassette Fly Reel
Competition fly fishing is a whole different ball game and beyond the scope of this article. However, for the casual fly angler who is unsure about what tactics to use when the conditions are very warm, the information presented above can be very useful. It will definitely be worthwhile extending your comfort zone and moving beyond your trusty floating line tactics and embracing the fast sinking line method. It can also make the difference between packing up early "because nothing is happening" and thinking "it's bright and warm, so they must be down deeper." Just switch to your Di7/8, move around, fan cast, and search the deeper water. You might just surprise yourself!

If you would like more information or advice about how to fish in very warm conditions, what flies to use, the best fly lines to buy etc, visit us in store at Glasgow Angling Centre, where we have some of the UK's best competition fly anglers on hand, and a highly experienced team of fly anglers who have fished all over the UK and beyond. Or if you are in the Edinburgh area, don't forget we have a great team of guys in Edinburgh Angling Centre who would be happy to help you.

This article was brought to you in association with Trout Fisherman Magazine.