Over much of the West in this dry and smoky season, those who wish to fish will be laying their lines out over the flat, featureless, silver skin of a lake. Most of these hapless anglers will be fishing blind, or even worse, mindlessly trolling something like a Woolly Bugger behind a float tube. In the fly-fishing scheme of things, these constitute cruel and unusual punishments. It doesn’t have to be this way.
There is no crime in drought, and there is no punishment in fishing a lake if done with purpose and reason. At this very moment, I am sprawled atop a quilt of lush green grasses, wild strawberries, yarrow, and lupine and writing these words under the shade of an ancient, storm-gnarled alder on the banks of a chuckling river in the mountains of Wyoming. The river is full, the water is cool, and a slow, but steady infusion of flying ants, Pale Morning Duns, and spruce moths is going with the flow. Not 20 feet from the soles of my bare, fly-bitten feet, small, but chunky cutthroats methodically rise. On purpose, I carried a pencil and pad of paper today and not a fishing rod: the rod is inside the boat, hitched to the truck, parked miles away at the trailhead in another state.
Unlike much of California at this moment, here, there is an embarrassment of trout-filled rivers, creeks, and streams in the near vicinity to fish, but I choose instead to fish the lakes frequently. Lakes are not a second-best option forced upon me by hoot-owl closures or crappy river fishing conditions. I don’t have to fish these lakes — I want to. (In the interest of full disclosure, I will admit that while I am “at work” writing this article, Lisa is fishing the creek. She would fish in a cattle trough, if it had rising trout.)
Counterintuitively, lake fishing can be far more dynamic, technically challenging, and intellectually demanding than casting bugs on a river. A river pretty much tells you where the fish are going to be and how to present your offering. River fish are going to be under the undercuts, in the pillow at the front of a rock, inside the seams, and astride the eddies. By comparison, unless rising fish provide direction, most lakes appear to be bowls of water — blank slates that the majority of fly fishers approach with nothing more than a lucky hat and a wing and a prayer. Consider this: a lake is not simply a bowl of water, but a bowl of water steeping under the sun. The sun heats the uppermost layers of the lake, while the deeper layers remain relatively cool. I say “layers,” because that is exactly how a lake is warmed. Warm and cool water don’t meld, but stratify. Trout exploit stratification as much as they do pillows, undercuts, and seams in a river. The uppermost layers of a lake are not only warmed, but energized by the sun through the magic of photosynthesis. Billions upon billions of solar-feeding algae hover in suspension and gorge upon the photons that blast the sun-rich layers of every lake, and in turn, they are feasted upon by aquatic herbivores such as copepods, Daphnia, snails, tadpoles, and many species of fish.
The upper layers of lakes are oxygenated by the direct air-to-water interface, but sometimes more importantly by the oxygen-rich exhalations of algae. The upper strata of the lake, where solar energy is converted into nutrients and where oxygen is abundant, thus are where the action is. Conversely, the lower strata of the same lake, trapped beneath the warm and buoyant layers of water above them, cannot benefit from the air-water interface, nor does the sun penetrate with enough force to drive a meaningful level of photosynthesis. The deepest waters of many lakes are nearly devoid of oxygen and cannot support fish life.
When a wind-blown leaf settles on a lake’s surface, it scuttles to and fro like a tiny boat bullied by the breezes. After some amount of time, the leaf succumbs to the embrace of gravity and sinks into the oxygen-deprived depths, where it settles on the cold lake floor, a tiny, but power-packed battery of solar energy waiting to be freed. Throughout the summer, a multitude of leaves and dead organisms silently gather in the mud with their store of collectively enormous potential energy and patiently wait for the unleashing.
The unleashing usually happens during the reign of the harvest moon. The sun’s energy has waned to the point where the upper layers of the lake aren’t nearly as warm and buoyant as they were throughout the hot summer months. The density gradients between warm and cold layers are weak, and when the first fall winds arrive, the lake’s water is set in motion. Millions of tons of water are pushed by the wind and slide across the surface of the lake, hit the downwind bank, then dive into the depths. The thermal stratification is fractured, and the dead things come to life. Oxygen-rich water swirls through the nutrient-rich depths, and the formerly hypoxic barrens of the lake bed become populated by every feeding organism, from bacteria to snails to trout. In this process, known as “turnover,” the lake explodes with life, and a feeding frenzy ensues. It is a nice time and place to be armed with a fly rod.
Lakes not only stratify vertically in parfaitlike layers, but also stratify from the shallows to the depths. Shallow water gathers heat much more quickly than does deep water, because the mud and the rocks act as heat sinks, absorbing the sun’s energy, and they then emit long-wave radiation back into the water. The warm shallow water does not meld with the cooler deep water, but stratifies from bank to lake in temperature-specific bands. The edge of each band acts as a thermal gate where drifting dust, pollen, leaves, and bugs are allowed to leave the cool water and enter the less dense warm water, but are trapped by the density differential of the thermal gates and cannot drift back out into the denser cool water. Like Hotel California, the bugs can enter, but they can never leave, and unlike me, trout never get tired of that song.
When hatches or wind-blown insects aren’t satiating trout elsewhere, the fish will haunt the warm edges of the lake in search of bugs trapped inside their thermal prisons. When a breeze strong enough to blow the warmed shallow water into deeper water arises, the warm water will float atop the cooler, relatively denser water, and carry with it its burden of trapped dust, pollen, leaves, and insects. Trout will follow.
The warm cells can easily be identified by any angler in the know. They look like islands of calm water floating amid a lake of small waves or breeze-driven ripples. The junk trapped in the warm water acts as a surfactant, which breaks down the water’s surface tension and prevents ripples from forming. Many times you can see such islands of leaves, dust, or pollen drifting about. Now you know the reason why these pockets of debris are drifting in islands, rather than evenly dispersed over the water. This is where the bugs are and where the feeding fish will be. Consider these spots as casting targets.
Where a creek enters a lake is generally a good place to fish. Not only the aquatic insects that dwell in the creek itself, but the unfortunate terrestrial insects who fall into the creek will be carried into the lake. If the creek water is warm, it and its bounty will float out over the cooler lake. Use a floating line and keep your offering near the surface. If the creek is cool relative to the lake, its dense waters will immediately sink, carrying the bugs with it. Go for a sinking line, or at least a weighted fly, to get down deep where the hungry trout will be feeding.
If it is windy, consider if there is a hatch of mayflies or midges happening on the lake. If so, fish from the downwind bank in anticipation that many of the emergers and hatchling adults will get blown with the wind and concentrated at your feet. If terrestrials such as grasshoppers, flying ants, or moths are abundant, consider fishing from the upwind bank, with the wind at your back to take advantage of the natural chum of weak flying insects that get blown onto the surface of the water.
With just a modicum of understanding how sun, wind, and water interact with one another, you will never again face another lake and view it as a bowl of water or a blank slate. It is a slate covered with instructions written in code and with invisible ink that you will be able to read clearly if only you take the time to look and think. Welcome to our secret club. Even after the rain and snow return, you might never fish a river again.
