SANDUSKY -- Lake Erie's prodigious walleye herd gathers in the extreme western end of the lake early each spring to spawn on the reef complexes, in Sandusky Bay, or in the Maumee and Sandusky rivers.
Once that instinct-driven ritual is completed, many of the walleyes are on the move, with the fishermen close behind in varying degrees of hot pursuit.
The chase that ensues often works like the predominant weather patterns, moving steadily west to east as the lake warms with the summer months.
The shallow Western Basin becomes less comfortable for many of the larger walleyes, so they generally migrate to cooler water in the Central and Eastern basins.
But connecting the dots on the walleye puzzle map is never a black-and-white or straight-line exercise.
"There's not really a solid formula, per se, for the way these fish move around in the lake," said Chris Vandergoot, fisheries biologist with the Ohio Division of Wildlife's research unit here.
"There is some type of environmental queue, but it's not just water temperature, and we're not sure it's based on the forage fish available. It is likely some combination of a number of factors."
Vandergoot said some of the Erie walleyes will move rapidly toward the deeper Eastern Basin immediately after they spawn, while others soon migrate up the Detroit River and into Lake St. Clair and beyond. A significant amount of fish remain in the western end of the lake, with their movements often difficult to predict.
"But what we do know is that as summer wears on, we see less and less big fish in the Western Basin," Vandergoot said.
Come July and August, where charter captain Ross Robertson sees those big, hog walleyes is often to the east. But he agrees with the biologists that have made the study of Lake Erie's walleyes their life's work -- there is no yellow-brick road that always leads to a cache of huge fish.
"People might give you simple answers, but those are not good answers," Robertson said. "There's nothing simple about it."
Robertson, whose nearly two decades of fishing on Lake Erie and his time spent learning under the guidance of legendary walleye angler Jim Fofrich have pushed him toward the top of the profession, has spent most of the last couple of months fishing between Geneva-on-the-lake, Ohio, and Erie, Pa.
"I'm not one that really follows the water temperatures so closely, because I think it's more about the food," Robertson said. "For me, everything resorts back to the food, and when those baitfish are there, the big fish will usually be there, wherever that is. It's not the case with all of the walleyes, but it seems like there's one or two big waves a year and you can almost follow them down the lake as they move east."
Lake Erie offers its big walleyes a wide range of depths and water temperatures.
The Western Basin, roughly from a line connecting Point Pelee on the Ontario side to a little east of here on the U.S. shore, then west to Toledo and the Michigan shoreline, averages just 24 feet deep and warms quickly as summer arrives.
The Central Basin extends east to just beyond the Ohio-Pennsylvania line and averages 60 feet deep, while the Eastern Basin is roughly defined by a line from Erie and Long Point, Ont., to the lake's end at Buffalo, with an average depth of 80 feet. The Eastern Basin has the lake's deepest water -- in excess of 200 feet -- in the Long Point Escarpment, a narrow trench northeast of Erie.
The big lake also offers a variety of food for the walleyes' plate, with a somewhat "regional" delights menu. Vandergoot said that as the walleyes cluster in the Western Basin for the spawning period, a lot of small white perch and yellow perch make up the meal plan, with gizzard shad and shiner minnows filling a good chunk of the walleyes' diet as summer arrives and the fish move east.
Once they are marauding around in the eastern waters of Lake Erie, the big walleyes' diet is focused on rainbow smelt. Most of the monster walleyes Robertson hooked up with last week in the deep waters off Erie were full of smelt when they came to the landing net.
Vandergoot said the larger the walleye, the more temperature sensitive the fish is likely to be, so he expects the big fish in the Eastern Basin have found their comfort zone and are working up or down in the water column to attack the schools of smelt.
"It's all about thermal regulation -- these fish want to optimize the conditions," he said. "These larger fish need cooler water."
When in pursuit of these big walleyes in the eastern waters of Lake Erie, Robertson said he prefers to fish spinners with heavy in-line weights or snap weights, and work the rigs at speeds slower than 1.5 miles per hour.
If the white bass and white perch prove to be too much of a nuisance, Robertson pushes the speed of the troll up to as much as 2.3 mph and uses crankbaits or spinners rigged on dipsy divers or very heavy weights.
On the recent expedition out of Erie, Robertson and Pennsylvania-based tournament fisherman Bob Henton were fishing in water up to 120 feet deep. They were locating suspended fish holding in the cooler water at the thermocline, about 40 to 60 feet down, where the water temperature changes from the warmer layer nearer the surface to the colder bottom temperature.
The duo, while filming a segment for the Field and Stream television show Hook Shots, landed more than a dozen walleyes in the trophy class, with one going 31 inches and 11.25 pounds and another at 30 inches and 10.5 pounds.
All of that came on a day shortened by the clutter and idle time that are the companions of working film segments. Robertson also noted that there were "zero" additional boats fishing the area where he and Henton were dredging up the big walleyes, often referred to as "The Trenches."
Roberston said he believes that the big walleyes have been on the move more in the last five years, but that the Lake Erie fishermen are also more savvy and competent in their pursuit today, especially with the wide array of high-tech equipment at their disposal.
"But what seems to be holding some of them back on chasing these big fish is that a lot of the walleye fishermen are scared off by the deeper water," Robertson said.
"Their comfort level is in shallower water."
Robertson, whose approach is detailed at the http://www.bigwater fishing.com Web site, readily admits that the big walleyes of Lake Erie are the ultimate moving target. He was back fishing on the Ohio side of the big lake by week's end, ready to migrate at a moment's notice if the big walleyes dictated such a redeployment.
"You can usually look at the calendar for next year and have a pretty good idea where we will be fishing on certain dates, based on what we've seen these big fish do over the year," Robertson said. "But these are fish and there's never an easy or certain answer on what they are going to do. Next month could contradict all of this."
Contact Blade outdoors editor Matt Markey at: firstname.lastname@example.org or 419-724-6068.