MANITOU BEACH, Mich. -- On an otherwise bragging rights kind of late summer day, there were only a half dozen boats scattered about Devils Lake, a popular and productive fishing hole in Lenawee County.
When the water heats up and the vegetation spreads out, those seemingly effortless angling days are over. A lot of fishermen who were out here for the easy pickings in the shallow water in spring and early summer have relegated the rods and reels to a dusty corner of the porch and given up the chase.
But that does not indicate that the fishing is too tough to be productive.
John Zuelke will tell you that he is probably as stubborn as he is experienced, and that means the retired Toledo beverage center owner has refused to accept the notion that hot weather, warmer water and lush aquatic plant growth translate into an empty fish cooler in July, August and September.
"There's good fishing here," Zuelke said after a recent morning outing on the 1,300-acre lake. "The fish don't stop biting - the fishermen just stop fishing."
Zuelke, who fishes Devils Lake nearly every day, said he too struggled at times with the catching part of fishing once those notorious dog days of summer were staring at him from the calendar.
But he persisted, refusing to believe that the prolific population of bluegills in Devils Lake would just turn off come the first of July and not be heard from again until the ice fishermen started pock-marking the lake in January.
"I don't know much about all of the science behind it, but the way I figured it, if you don't find the fish in one place, they have to be somewhere," Zuelke said. "They don't leave the lake, but they just get a little more challenging to locate as the summer wears on."
Well, when fishing and science merged for Zuelke, he got to know the thermocline, and he started to find those reclusive late summer bluegills, in numbers.
Score another one under the heading of "old dog learns new tricks."
Zuelke and his wife, Cheryl, don't just live on Devils Lake, they live Devils Lake. They are active in the Devils and Round Lakes Preservation League and are volunteers in the Cooperative Lakes Monitoring Program run by the Michigan Department of Environmental Quality.
In the latter role, Cheryl conducts regular water tests on the lake, which is located about 13 miles northwest of Adrian in the Irish Hills area. Using an instrument with sensors that are calibrated to the current weather conditions, she gets readouts that reveal water temperatures and oxygen levels at numerous levels below the surface of the lake, which has a maximum depth of 63 feet.
The data is entered into a Web site and the water samples she collects are frozen for shipment to the state for further testing. But those temperature and oxygen level numbers are shared with the fisherman in the house.
Once he has a pretty good idea where to locate the thermocline -- that invisible layer in the depths that separates the oxygen rich, warmer upper layer or epilimnion from the oxygen starved and colder lower layer or hypolimnion, Zuelke's fishing savvy takes over.
He puts tiny markers on his line so he can fish at exactly 24 feet, if that's what the data tell him will place his baits in the neighborhood around the thermocline. And the fish are usually in that region of the water column, if he works enough of the lake to find their preferred hang-out on that particular day.
"They might stage in one area for a while, but eventually they will work their way around to a lot of the same areas," said Zuelke, who estimates that he catches between 800 and 1,000 bluegills most years on Devils Lake.
"I used to go out and set my line at different depths, and do a lot of trial and error," Zuelke said. "But having the science behind it -- this way is easier."
The preferred water temperature, level of light penetration, and the location of food sources will always be part of the formula and vary according to the species of fish, but Zuelke is convinced that in summer and early fall, knowing where the thermocline is located is the smart first step in the hunt.
"I fished a lot of years without that information, but having it sure makes things easier," he said. "It takes some of the guessing game out of fishing."
WING WATCH: The Lake Erie Wing Watch weekend for birders will be held Sept. 22-23, with a wide range of activities for children and families taking place at locations throughout the region. Ottawa National Wildlife Refuge, Magee Marsh Wildlife Area, Old Woman Creek National Estuarine Research Reserve, and both South Bass Island and Kelleys Island will host events connected to the Wing Watch. For details, visit LakeErieWingWatch.com.
Contact Blade outdoors editor Matt Markey at: email@example.com or 419-724-6068.