July 24, 2015
By In-Fisherman
Editor's Note:
Wind is friend and foe, fearsome force for good fishing and bad, an ever-present factor affecting when, where, and how we fish for walleyes. The sun ultimately is responsible for currents in bodies of water. Temperature variation in different levels of the atmosphere causes winds. The interactions of the earth's rotation on its axis, its revolution around the sun, and the movement of our solar system produce global wind patterns.
On either side of the equator, winds typically blow from east to west — the trade winds that powered mercantile fleets of yesteryear. North of the 40th parallel, which runs roughly through Philadelphia, Indianapolis, Denver, and Redding, California, winds blow predominately from west to east — the westerlies. These are the potent blows that whip the western plains and gather momentum as they cross Middle America and sweep past the Great Lakes toward the East.
Add to this mix the Coriolis force, which is generated by the rotation of the earth and causes air and water to deflect to the right in the northern hemisphere (left in the southern hemisphere). The intensity of the Coriolis force is based on latitude — nil at the equator and increasing toward the poles.
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Coriolis Force
A half day or more of wind from a consistent direction usually creates a current moving toward structural elements on the windward side of the lake. But Coriolis force bends water currents to the right of the wind direction. In large lakes like Ontario and Superior, the current bends as much as 45 degrees.
As lake size and depth decrease, the angle of deflection is reduced. Limnologists studying 9,600-acre 80-foot-deep Lake Mendota (Wisconsin) found currents deflected about 20 degrees to the right of the wind. Assume then that in most lakes the deflection is slightly to the right.
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Not only is the surface current not moving in the same direction as the wind, but a substantial subsurface reverse current is moving in the opposite direction of the wind, so 10 to 20 to perhaps 30 degrees farther to the right. First figure the to-the-right deflection of the surface current; then note that below this surface current a reverse current rebounds like a pool ball bouncing off a cushion at another angle to the right of the surface current.
This often overlooked current affects walleye position near middepth structural elements. Fish in shallow water usually face into shallow surface current. But fish holding deeper than about 5 feet often face the opposite direction — into a reverse current.
Say the wind is blowing onto a bar that drops abruptly into 4 feet of water just offshore, then slopes to 10 feet, then plummets to 30. The tip of the 10-foot drop-off is a key area. Most fishermen consider the wind and the wind-generated current washing this bar. And because walleyes usually face into current, they picture walleyes facing the wind.
The direction walleyes face affects presentation. Presentations should move toward or quarter in front of walleyes, instead of sneaking up on them from the rear. In this case, most walleyes probably face the rebound current moving in the opposite direction of the wind. Retrieving baits offshore should be more productive.
Currents that hit shorelines also are deflected clockwise, which affects fish position and location. Say you' re fishing a plateau reservoir — could be any body of water where walleyes gather along wind-blown shorelines. Wind blowing into shore produces a right-moving current. Follow the shoreline drop-off to the right until you meet a bar. The inside turn on the side of the bar that meets the current likely holds active fish. The tip of the point on the current side of the bar also likely holds active walleyes.
But in early spring or late fall when the water's cold and the fish aren't active, the back side of the tip of the point (a bit removed from the current) more likely holds fish. Perhaps the side of the inside turn away from the wind-caused current also holds inactive fish.
Don't troll crankbaits into surface current deflected along the shoreline. Troll with the subsurface current, in this case coming into the inside turn or coming into or along the tip of the point.
Consider this scenario from a different angle. The surface current is moving slightly clockwise of the wind. To work the deeper-lying rebound current moving even more to the right, move with the wind, but slow your approach with driftsocks or your outboard motor. Use your outboard (or electric trolling motor) to adjust your direction of drift.
If these scenarios confuse you at first, sketch a lake. Draw the wind direction. Add arrows slightly to the right to depict the general direction that surface water flows.
Where this current contacts a shallow bar or bank, draw surface current channeled to the right along the shore or bar. Now add arrows to depict a rebound current deflected almost in the opposite direction — again, this current is deflected clockwise and runs deeper. Now draw walleyes facing this deeper-lying current. Also draw fish facing the surface current, particularly where it contacts sharp-breaking structural elements.
Suppose you anchor to cast jigs to fish positioned at the tip of the 10-foot drop-off. Consider their position probably facing into a rebounding current caused by the wind. Cast past the fish and bring the lure toward them or quartering in front of them. A good option is to anchor off the point in deep water and cast into the shallows, bringing the jig from the flat toward deeper water.
Surface wind pushes a slipfloat rig into the point, but this isn't the most effective way to move bait past deeper walleyes that probably are facing the other way. Correctly set slipfloats move slowly past walleyes; it's still an option to catch fish. Slip-float presentations are more deadly, however, where walleyes face into wind-caused surface currents at the edge or over shallow flats.
For most fishermen, factoring the potential effects of Coriolis force and rebound currents provides a new view of the real world of walleyes. But there's more.
Waves and -Surface Turbulence
What you're about to be told has never been a secret, has a major effect on fishing, yet remains a mystery to most fishermen. As wind causes the surface of the water to roll into traveling surface waves, little water actually moves laterally. Instead, the wind raises water and curls it in a circular pattern as gravity pulls the molecules downward — not unlike a wave traveling along a jump rope.
After wind has blown steadily for several hours, the tug of war between wind and gravity creates near--surface currents that move slowly, even in a strong wind. Watch, for example, the movement of neutrally buoyant debris — a piece of vegetation perhaps suspended just below the surface. The slow drift of an object just below the surface contrasts with a floating object, pushed by wind, that may move faster than 10 mph in a stiff breeze.
This surface movement, contrasting with the "stationary'' water below, is why drift-socks slow boats being blown over the surface of the water. A sock is a parachute anchored in relatively stationary water below. Drift speed can be cut by 10 to 90 percent, depending on the size of the drift sock (or socks) and the size of the opening in it.
The rolling action of waves creates surface turbulence, but only at a depth about twice the height of the waves. If waves crest at 3 feet, water at 6 feet is only slightly affected, though slow-riding currents may move through those depths.
The wave-caused zone of turbulence offers an important edge that focuses the activity of prey and predators. First, both prey and predators moving through open water may travel just below this edge. Secondly, prey like shad or bluegills, which were holding near the surface in calm conditions, are forced deeper along this edge as waves increase. Predators attack from below, forcing prey upward against the edge of turbulence. Prey forced into the turbulence lose equilibrium, schools break into disarray, and baitfish that break back into the stable water below are slightly disoriented and vulnerable to attack.
Wave length, which plays a role in the amount of turbulence, is the distance between successive wave crests. The typical ratio of wave height to wave length ranges from 1:100 to 1:10. A low ratio (1:100) causes swells, typical of calm days on the ocean. When wave height increases toward a ratio of 1:10 (choppy waves), whitecaps form as each wave collapses and water at the crest blows off as foam.
In small lakes, wave height at a given wind speed isn't related to lake depth. But in large lakes, wave height and wave length increase with depth. The maximum wave height is a factor of the distance the wind blows without interruption (fetch).
Waves may reach 8 or even 10 feet on Oahe Reservoir (South Dakota) or on Winnebago (Wisconsin). Lake Superior's vast area and depths to 1,300 feet produce the largest inland waves on the continent, up to 25 feet — woe be the Edmund Fitzgerald, which capsized and sank in a November gale that produced waves of that magnitude.
As waves approach shallow water, their velocity and wave length decrease because of the resistance of land. The circular motion of waves changes to an oval movement and then a back-and-forth slosh as waves crash as breakers. Across shallow flats or rock bars, wind-induced turbulence may extend to the bottom, forcing crayfish, larval insects, and bottom-dwelling baitfish from -shelter.
This shoreline turbulence creates important fishing patterns. Mudlines that form in reservoirs with clay or shale banks attract walleyes during the day. The best areas are on or near major structural elements — bars or creek channels that hold walleyes at that time of year. The fish hold in deeper water when the wind isn't blowing.
Once wind begins blowing into a shoreline, a rebound current sets up and sweeps into deeper water. Soon walleyes follow the current up onto the edge of the lip of the flat. Eventually, the fish may move across the flat and feed near the turbulence along the shoreline; that is, if the flat is deep enough to allow them to move in without being buffeted by wave-caused turbulence.
Walleyes tend to use shorelines with a lip — an immediate drop-off of a foot or two. Having found a shoreline with a lip, look for secondary structural elements such as rock piles or points along the shoreline.
Beyond this general pattern, look for more specific patterns caused by current generally moving to the right along windward shorelines. Active walleyes tend to hold on the current side of points and inside turns.
Another overlooked pattern for walleyes during summer occurs when wind sweeps weed-choked bars where baitfish usually lie hidden from walleyes. In lakes, most of these bars run 8 to 15 feet deep at the outside edge, where a weed wall rises almost to the surface to meet open water.
Once surface current bends the tops of the weed wall, it flattens weeds on shallower parts of the bar. If the directional wind continues into the evening, walleyes roam these bars at night. Often the fish hold just below the zone of wave-caused turbulence. In 2-foot waves, walleyes hold 4 to 6 feet down. In 1-foot waves, walleyes hold 2 to 4 feet down.
One option is trolling high-riding minnow-imitating plugs like the Cordell Red Fin far behind the boat. Or try a tandem-hook spinner rig (#3 Colorado blades) with a crawler, which catches fewer weeds. Better still, once you find a bar that holds fish, cast minnowbaits as you position with a trolling motor.
The Temperature Equation
The surface flows and rebound currents we've described occur during all seasons, warm water or cool. Combine these water movements with the different densities of water at different temperatures, and the effects of wind become even more significant.
Water is densest at 39°F, so at ice-out (surface temperature 34°F to 36°F) water readily mixes in moderate winds. As surface water is heated by the sun, it become less dense and floats on cooler water. This density gradient reduces circulation between layers of different temperatures.
Summer stratification into three layers is the large-scale result of warming and density differences. Even strong summer winds fail to mix these layers. But smaller-scale temperature variances occur.
On a sunny summer day, the top three inches of water may be several degrees warmer than water a foot down. And while swimming in a lake you encounter cold pockets that send you shivering to the surface. These same cold pockets may eventually be moved by wind-caused currents to areas that attract or repel walleyes.
A strong directional wind, for example, can pile a layer of warm surface water against a bank. During summer, this upper 70°F water may be too warm for coolwater species like walleyes or pike, causing them to shift deeper or move offshore even if schools of warmwater prey like minnows and shad are concentrated in the warmer water.
Due to gravity, this bulk of warm water squeezes out a mass of cooler, denser water lying just above the thermocline. The colder water sets in motion a rebound current that may concentrate coolwater preyfish like alewives or smelt.
Picture pockets of warmer or colder water as drops of oil in water. Colder, denser pockets tend to sink through warmer water. Warmer less-dense pockets tend to float on colder water. But both pockets can be moved by surface or subsurface current.
In the Great Lakes, fish follow temperature plumes or thermal bars that confine coolwater or warmwater prey. Savvy anglers use thermal bars to find trout and salmon miles offshore. Electronic temperature meters capable of checking temperature in the depths and infrared images drawn by satellites are valuable tools.
For Great Lakes walleyes suspended offshore, currents and water masses of different temperature are important because of their effects on preyfish and walleyes. But they're also important on smaller waters.
A cold rebound current eventually may be forced toward the surface by an offshore bar, forming a cold pocket of surface water surrounded by warmth. With or without an influx of prey, this new water may stimulate activity by walleyes. Due to its greater density, this cool pocket drifts downward. But it may be renewed over hours or days by continuing cool currents.
At wind speeds between about 5 and 15 mph, a phenomenon called Langmuir circulation may also occur. Currents near the surface form columns of convection as surface water is pushed over slightly cooler water below. The surface water turns downward, forcing cooler water up. Langmuir currents are visible as streaks on the surface that align slightly to the right of the wind direction (again due to the Coriolis force).
These streaks contain floating debris, including algae, pollen, and invertebrates. Between the streaks are zones of upwelling, where cooler water from the depths is forced to the surface. In oceans and the Great Lakes, upwelling areas are among the most productive fisheries. On smaller lakes and reservoirs, these areas also are productive. Concentrations of microorganisms in the streaks draw baitfish that in turn draw predators like walleyes.
Wind-induced currents are subtle, but temperature variances are invisible. The first step is recognizing that these thermal bars and upwellings occur in lakes and that they can affect the location of preyfish and walleyes. Systematically charting and anticipating these shifts is an advanced step few walleye anglers have taken.
Walleye anglers have increasingly focused on open-water walleyes. The next breakthroughs in using temperature profiles to find walleye is likely to occur in Lake Erie, Saginaw Bay, Bay of Quinte, and other big waters. Fine-tuning these techniques to small lakes provides a challenge well into the 21st Century. â–
