It’s fair to say that the majority of trout feeding in lakes occurs subsurface. The majority of feeding will place in water less that about 35 feet in depth simply because the highest concentrations of trout food, the macro invertebrates live in shallower water. The perfect stillwater has a balance of shallow and deep areas. The shallows or shoal waterwill have extensive vegetation growing along and off the bottom thus offering ideal habitat for scuds, chironomids, mayflies etc while the deep water zone is home to zooplankton, seasonable midge and boatmen populations but more importantly it is a refuge for trout to escape predators as well avoiding the warm or hot summer periods. The spring and fall periods allow trout to feed almost anywhere in the lake but foraging is most concentrated within the shoal and drop off areas which allows considerable use of floating lines and sinking flies. However, the edges of the drop-off and the main deepwater zone of the lake are often more effectively covered with sinking lines that get flies down to the depths at which fish are holding. As well, certain food sources such as dragonfly nymphs, scuds and caddis larvae, live in the benthic areas which can often be better covered with full sinking lines.
Choosing the Right Sinking Fly Line
Full sinking fly lines designed for stillwater applications are available in a wide variety of densities or sinking rates from slow/intermediate type 1 to extremely fast sinking type 7 lines. Each line has an identified sink rate measured in inches/second. Slow/intermediate lines (type1) sink at between 1 and 2 inches/second whereas the deepwater or dredger lines (type 7) are sinking between 6 and 9 inches/second depending on line weight. Sinking lines are also available in regular sinking where the thinner tip section sinks slower than the thicker and heavier mid or belly section or in density compensated in which the entire line sinks at a uniform rate. Both line designs have applications in stillwaters.
Type 2 (fast) and type 3 (extra fast) sinking lines are good for fishing deeper edges of drop-offs, deep water chironomid pupa emergences and covering the mid water areas of the lake. Dragonfly nymphs, caddis larvae and scuds are all bottom dwellers and these faster sinking lines will get the fly down and allow retrieves to be made along or just off the bottom. An ideal situation for the type 3 line is to be retrieving patterns up the face of the drop-off. For example, a dragonfly nymph could be slowly stripped up the face of the drop off, starting in perhaps 25 feet of water and ending up on the bottom in 5 feet, just like the real mature nymphs do when on their emergence swim. The steep incline faces of drop-offs are ideal to fish with density compensated sinking lines as the angle of ascent of the dragonfly nymph, for instance, can be closely matched to the actual slope of the drop-off.
Type 2 and 3 non-density compensated sinking lines are also very effective to fish deep water chironomid emergences. Hatches occurring at depths of between 25 and 35 feet are ideal for this technique. The chironomid pupa is cast out as far as possible and the fly line is allowed to sink for the amount of time it will take for the main body of the line to reach within about 3 feet of the lake bottom. For example, if we were fishing a type 3 line which sinks at 3 inches/second and our boat is anchored in 30 feet of water we would wait approx. 120 seconds before starting a steady but slow retrieve. Because of the way this fly line sinks the chironomid pupa will be retrieved across the bottom of the lake for a short distance before beginning an almost vertical ascent to the surface of the lake. Trout often take the pupal pattern just as it is making the turn upward.
The same two lines are also the ones of choice for imitating the diving/swimming action of water boatmen and backswimmers. These air breathing insects will fly from one lake to another, dive into the deeper areas while on swarming and egg laying flights in the spring and fall. The belly created while regular sinking or non-density compensated lines sink can be used to imitate the downward and then upward swimming action of these bugs.
Super fast sinking type 6 and 7 density compensated lines are really effective in probing the very deepest parts of the lake or in situations where the fly needs to get down fast before a retrieve is initiated. One example is when trout are working schools of baitfish. Trout will sit under or to the sides of bait balls that may be suspended down 20 to 40 feet. These lines get down quickly and allow a straight line ascent at an angle determined by the length of time the line is allowed to sink. The fast sinking nature of these lines can also be put to good use when fishing creek mouths as they again allow coverage of all depth ranges that could hold cruising fish. The other usage scenario is fishing dragonfly nymphs or attractor pattern such as boobies in very shallow water. This is often a sight fishing situation where we are casting well ahead of a fish that is swimming in 4 to 10 feet of water. We want the fly line to sink right down to the bottom so that the fly is retrieved along or just off the lake bottom. It is an adrenaline rush to watch a big fish chase down your fly and eat it.
Deep water chironomid emergences occur in many productive lakes. These pupae are emerging from the bottom of the lake at depths up to 60 feet. Super fast sinking lines (type 6 & 7) are used to quickly take pupal and larval patterns down to these depths. Once there, the flies can be retrieved straight up to imitate the naturally ascending pupa or they can be kept near the bottom to imitate the pre-emergence staging that often occurs with chironomids. In this situation the pupal pattern is twitched up and down within a foot of the bottom or slowly inched upwards for a few feet then allowed to sink back down.
All of these sinking line tactics are based on knowing the depth of the water being fished. We can calculate the sink time to reach the bottom because we know the specific sink rate of each line and the depth being fished. As well, knowing the sink rate of a particular line will allow flies to be presented at any depth zone between the surface and bottom. It definitely pays to take the time and develop the patience to use a watch to time sinking rates thus knowing where your fly is fishing. This further emphasizes the value of depth sounders/fish finders for the serious stillwater angler.