It was not that many years ago that planning a summer holiday around some lake fly fishing was considered a really bad idea, as the fishing was most likely going to be unproductive. Stillwater fly fishers have since learned a lot more about trout behaviour and feeding strategies, to the point where those anglers in the know are able to have some great fishing and catching action during what has historically been referred to as the “summer doldrums” period.
In BC, our most productive trout lakes are found in the interior regions of the province, where nutrient-rich water creates an ideal environment for growing fish, as well as their favoured food sources. These lakes also endure a long, hot summer season, which has a direct bearing on trout activity levels and feeding behaviour. These warmer water temperatures also influence the aquatic insect emergences that are so prolific in these waters. By mid-summer, the majority of hatches are over, leaving only sporadic emergences of chironomids, damselflies and dragonflies. The one exception are the intense late summer emergences of very large chironomid species that we refer to as bombers. This hatch occurs on a number of shallow lakes scattered throughout the southern interior regions.
The arrival of the hot summer season does not stop trout from feeding, but their foraging tactics change in direct response to changing environmental conditions. Trout, like all other fish, are cold blooded and that means seeking out water that meets their physiological requirements for survival. For trout and char inhabiting small lakes, this means cool, well-oxygenated water. So as the upper layers of the lake heat up during the summer, the fish will move deeper in the water column to find temperatures that are cooler and supporting adequate oxygen levels.
Prime Summer Habitat
It’s important to understand the structure of a typical small trout lake in order to know where to concentrate fishing efforts at various times of the season. Imagine the lake as being shaped like a pie plate. The edges of the plate gradually slope off to the deeper middle section, then slopes back up again to the opposite side. On a lake, the shallow water area is known as the shoal zone and the horizontal distance of the shoal can be short or it can be quite extensive. The shoal zone does offer the most productive fish food and fish habitat of the lake and it is the area where fishing is best during the spring and fall seasons. However, during the summer months, on many small lakes, the shoal becomes too warm for trout to frequent on a continuous basis.
The point at which the shoal slopes off to the deep water is referred to as the drop-off. The slope down to the deep water can occur gradually or it can be abrupt and steep. The middle portion of the lake is referred to as the deep-water zone. The drop-off zone becomes prime habitat for trout during the warm summer months. Depth wise, this usually equates to water five to seven metres in depth. Here, the water is much cooler than that of the shoal, so oxygen levels are higher, plus photosynthesis still occurs and allows green plant life to flourish, which provides valuable habitat for many key trout food sources. In essence, the drop-off zone provides the ideal summer refuge.
Summer Diet Options
As summer progresses, trout become more and more opportunistic feeders. Fish actively search out food hiding amongst the vegetation and bottom substrate at depths where they are comfortable feeding and can avoid predators. Immature damselfly and dragonfly nymphs, leeches and shrimp become staple food sources. As well, mid-water concentrations of zooplankton, such as daphnia, are an easy meal and often targeted particularly during the warmest periods of the summer.
Summer Fly Fishing Tactics
Summertime fishing means covering a variety of depths which can still be fished with floating lines, but a variety of different sinking line densities will be required to present flies deeper and along the lake bottom. This is the time to concentrate much of your fishing efforts in the drop-off zone of the lake. Just think of this habitat zone as a fish feeding highway that trout can travel along and parallel to or move vertically up and down the face of the slope.
One of the most effective fishing tactics is to anchor up broadside right at the transition of the shoal and the leading edge of the drop-off. From here, one can fan cast out into the deeper areas of the drop-off and retrieve flies up the face of the upward-sloping lake bottom. Dragonfly nymphs, damselfly nymphs, leeches and shrimp are all good flies to fish at this prime location. The density of sinking fly line chosen is dependant on the gradient or angle of the slope being fished, as well as the anticipated speed of your retrieve. If it is a very gradual slope, then a type 3 full sinking line would be more effective than, say, a type 7 sinking line, as the slower sink rate will allow the fly to be retrieved at the appropriate pace just off the bottom for a much longer distance. A very steep angled drop-off may be better fished with a type 5 or 6 full sinking line. Again, we want to present our flies as close to the bottom structure as possible, as that is where these food sources are living. Regardless of the sinking line being used, it is important to ensure your fly has reached the intended depth zone before beginning any retrieve. The number associated with your sinking line indicates the sink rate per inch of that line, so you can calculate the time it will take for that line and your fly to reach the bottom of the area being fished. This is where a depth sounder becomes an important tool for the stillwater fly fisher, as we always want to know the depth range of the water being covered.
Another way to effectively fish the drop-off is to anchor along or perpendicular to the face of the slope and then cast and retrieve your fly that targets a specific depth. With this technique, you can start fishing the shallower or top end of the drop-off and gradually move down the face of the slope to cover deeper depth zones. Having anchors out the bow and stern of the boat will ensure you are able to properly present and maintain control of your retrieve.
Floating lines and strike indicators can also be used to fish the drop-off zone. Suspending leech, damselfly nymph and scud patterns just off the bottom and slowly moving the fly either by wind drifting or with an intermittent retrieve will give any nearby fish lots of time to commit to taking your fly.
Fishing The Deepwater Zone
During the heat of the summer, trout are also found feeding in the deeper areas of the lake. This is where the minute crustacean known as zooplankton are often found in large masses or congregations. One of the most common zooplanktors is daphnia, which are commonly referred to as water fleas. They range in colour from light olive to orange to almost a dark maroon. These tiny crustaceans can be seen dancing in the water as you look down over the side of your boat. Individually, daphnia do not appear to be a significant food source, but when large numbers of them gather into mid-water clusters they become an easy meal for many species of fish. Daphnia are known to vertically migrate up and down through the water column. They are typically found in deeper water during daylight hours and much higher in the water at night or during low-light conditions. Daphnia are a favoured diet item for kokanee, as well as trout. Fish swim lazily through these dense concentrations of these tiny crustaceans and filter them through their gill filaments before passing them into their gullet.
Size wise, daphnia barely reach three millimetres in length, so tying flies to imitate them is next to impossible. Some success can be had with patterns that imitate a cluster of these minute crustaceans or by stripping brightly coloured attractor-style flies up through the water column. More recently, anglers have discovered that blob patterns, originally developed by UK anglers, can be very effective for fish that are targeting zooplankton. These rather non-descript flies really look like a gob of brightly coloured yarn that has been wrapped onto a hook. But these simple-looking patterns work and will often save the day when other patterns and techniques are only nominally successful.
One of the most effective ways to fish a blob is to suspend it under an indicator. A typical fishing situation might see being anchored in 10 metres of water and suspending a blob down at six or seven metres. Your depth sounder will help in marking fish, as well as the bottom depth. Fish the blob just like a chironomid pupa and watch for the subtle take as the indicator goes down. Blobs can also be cast and retrieved on full sinking lines with the goal of retrieving the fly up through the depth zone that the fish are suspended and feeding. Vary your retrieve from slow, five to 10-centimetre-long steady strips to short and fast strips with regular pauses thrown into the mix. Some of the most consistent blob colours include prawn, biscuit, chartreuse green, coral and sunburst orange. There are several material companies producing blob tying materials, so check with your local fly shop for their availability. You can now buy commercially tied blob patterns, which is further testament to their effectiveness in BC waters.
Dragonfly nymphs and leeches can also be effectively fished in the deepwater zone, which could be in the middle of the lake even though this is not the normal place to find either of these food sources. Trout recognize these staple food sources and will view them as an easy, opportunistic meal. Don’t be afraid to cast and retrieve your favourite dragonfly nymph or leech on a full sinking line or suspend a balanced leech under an indicator. You could be pleasantly surprised at the results.
Take advantage of the feeding strategies and diet preferences of trout during the warmest months of the year when planning your next summer camping trip to one of the many interior lakes of the province. There is a good chance you might be extending your vacation because the fishing is so good.