Simply referred to as “Kosh” by the many anglers who ply its waters, Lake Koshkonong, in Jefferson County, Wisconsin, has evolved from a lush, clear-water waterfowl marsh filled with wild rice, wild celery and other desirable types of vegetation in the 1880s into what is today—a murky, shallow-water expanse on the Rock River.
The construction of the Indian Ford Dam, downstream from the lake, plus the intentional introduction of common carp by the federal government many years ago, are universally and equally blamed for the lake’s dramatic transition.
While this area was, and still is, a haven for wild ducks and geese, and attracts waterfowl hunters from all over the country, it also supports a robust walleye fishery—though its features are the farthest thing from a classic walleye lake.
“Koshkonong doesn’t get deeper than 7 feet,” says Team Northland member Adam Walton. “It’s silty, doesn’t have many weeds and 80% of the bottom is mud or muck; the rest is sand or gravel. And despite all that, I’d say that it’s among the Top 10 walleye lakes in Wisconsin.”
Walton, a fishing guide with Pike Pole Guide Service, grew up fishing on Koshkonong, and outside a stint in the military, has never lived more than a couple of miles from its shoreline. He and his partners guide anglers on Kosh, but more importantly, Walton’s lifetime of experience on the lake has given him a deep understanding of it and its walleyes, pike, crappies, white bass and catfish.
He describes walleye fishing on Koshkonong as “phenomenal,” but also explains that the fishery itself is delicate because it depends highly on stocking to supplement the limited natural reproduction that takes place. “Spawning habitat for these fish is limited, so the system must be stocked with walleye and northern pike produced by the Wisconsin Department of Natural Resources at the Bark River Hatchery in Fort Atkinson, and other facilities.” he says. “The DNR owns and runs the facility, but operating funds come from private donations by the Bark River Hatchery Partnership and other organizations. Since it started production in 1996, it’s placed an estimated 50 million walleye and pike fry into the system.”
Nature’s whims—exceptionally high water levels, or extremely high or low water temperatures—can mean the difference between a successful annual hatch of fry and an unsuccessful one, he explains. This occurred in 2016 when adverse weather and water conditions prevented hatchery technicians from collecting enough ripe female walleyes to operate the hatchery.
Likewise, fishing pressure influences the size/age profile of the lake’s walleyes. “When there’s a strong population of bigger fish, we see more anglers, especially since walleye fishing is open year-round on Koshkonong” he says. “We want people to come here and enjoy the fishing, but it’s important for anglers to practice selective harvest.”
History has shown that as fishing pressure grows, the number of larger fish in the system—the 20-plus-inch walleyes that are the backbone of the hatchery program—inevitably drops. “The lake has a 5-fish daily bag limit, with a 15-inch minimum size limit,” Walton adds. “There’s nothing wrong with an angler keeping any legal-size fish, but what many of us would like to see are more fishermen voluntarily releasing some of the bigger walleyes so they have a chance to produce for the hatchery system. Right now there are a lot of 12- to 17-inch fish from the 2012 to 2014 year-classes in the system and those 15s to 17s are perfect eater size. We just have to be sure to let some of those bigger fish go so they can grow.”
Walton and his partners adhere to a self-imposed slot limit, releasing any walleye from 18 to 25 inches in length. “If a client catches their first big walleye, or a young angler catches a large walleye, we’ll talk about keeping one trophy-class fish if it’s over 25 inches—though we do explain the benefits of going with a replica mount.”
1. Though ice fishing is a popular pastime on Kosh, sketchy ice conditions due to warmer than normal weather have recently put a damper on the activity. “For the most part, the lake freezes up pretty good even though the river runs through it,” says Walton, “and during a decent winter you’ll have 20-plus inches of ice.”
For walleye action, the guide recommends fishing Stinkers Bay from Carcajou Point to the Rock River inlet, or Gilbert Bay, on the south side of the inlet, down to Haights Bay during the early and late low-light periods. “Stinkers Bay is full of springs, which offer warmer water in the winter,” he says. “You can catch fish by vertically jigging, but because the lake is so shallow and the water is a clear as it gets all year, you have to be very quiet; even the sound of cleats on the ice as you walk will spook the fish. These walleyes tend to roam anyway, so you’re better off using tip-ups or tip-downs and letting the fish come to you.”
Walton suspends a medium-size shiner or black-tail chub on a chartreuse Super-Glo Easy-Set Hook under an insulated, cover-type tip-up that blocks light from entering the hole. “Use 8-pound fluorocarbon line with as little weight as possible so the minnow doesn’t tire out,” he adds, and suspend it 4 to 6 inches from the bottom.”
Koshkonong has a 2-fish daily bag limit and a 26-inch length limit on northern pike. When targeting these predators, Walton uses a Single Wire or a Quick-Strike Predator Rig, depending on the size of the baitfish, and hangs it under a rail-type tip-up that allows ambient light to reach the baitfish and the rig’s spinner blade. He recommends pursuing pike closer to shore, especially near marshes or river inlets. “We get into some pretty shallow water when fishing pike,” he says, “but we still try to work the whole water column. Pike often like to cruise high, just below the ice, so we set baits high, at mid depth and close to the bottom. Sometimes the water is only a couple of feet deep and the bait hangs just a few inches below the tip-up spool.”
Just off Otter Creek in Haights Bay is prime pike territory, he adds, but moving water in this area can make ice conditions sketchy. Use common sense and caution when fishing this area.
For winter crappies and the occasional bluegill or perch, the guide recommends fishing the west side of Stony Point. “There are springs along here, too, but again the water is shallow and the fish skittish. You can jig for them, but most anglers use tip-downs and stay very quiet on the ice.”
Walton likes fishing a 1/64-ounce Impulse® Rigged Bloodworm on 3- or 4-pound Bionic Ice® Fluorosilk when jigging for crappies, but tip-down options include a small leadhead, such as 1/32-ounce Mud Bug, tipped with a crappie minnow, or a plain hook-and-minnow rig. “
2. Ice-out on Koshkonong usually occurs in late March, but most anglers find the hottest early-spring walleye action in the Rock River. “The peak run usually happens around the second week of April,” says Walton. “There’s a lot of rocky, sandy and woody cover in the river, as well as deeper holes and feeding flats. The fishing is pretty phenomenal from the WI-106 Bridge (upstream from Ft. Atkinson) down to the lake.”
Walleyes travel upstream in waves, resting in deeper holes and feeding in the shallows, during the journey. The guide usually starts each day at the 106 bridge and fishes his way downstream, vertically jigging the holes and edges of holes, and pitching into the shallows.
Most holes along river bends run 8 to 12 feet, while the flats are typically 4 feet or shallower. Try jigging a Rock-It Jig, or a Fire-Ball® Jig (Stand-Up or Original) tipped with a minnow, he says, making sure it’s just heavy enough to stay vertical as the boat drifts downstream. A 3- or 4-inch Impulse® Smelt Minnow is another option. If the walleyes strike short, Walton adds a Sting’r Hook to the live bait rig, or cuts an inch or so from the head of the plastic minnow.
Sometimes walleyes want a larger profile, so the angler uses two Smelt Minnows, threading the first on the jig as normal. He cuts the second at a 45-degree angle from chin-to-dorsal and “tips” it onto the hook like you would a live minnow. “The angle-cut helps maintain a hook gap wide enough to let the barb sink in on the hookset,” he says.
For pitching the shallow flats, fancast a ballhead jig rigged with an Impulse® Swim’n Grub or Paddle Minnow. “Simply cast into the shallows and hop it or snap-jig it back toward the channel,” he explains.
3. Walleyes remain in the river as long as water temps and levels remain consistent, and the food sources hold out. Once any one factor changes, they start making their way back to the lake. “It changes every single season,” says Walton, “but generally speaking, we’re back in the lake when the temperature gets into the 60s.”
Warmer weather also brings changes to the lake. Water clarity in particular begins to fall off, and by the mid-summer dog days is just about zero. Because there is little structure or cover to concentrate fish, trolling for roving walleyes is the go-to technique. Many anglers troll hardbaits, starting with minnow-shaped lures, then switch to shad-body baits as the water warms. Run them a foot off bottom at 1.5 to 2.5 mph.
Dragging ’crawler harnesses behind bottom bouncers is another option. Walton suggests running a Walleye Crawler Hauler, with No. 4 Colorado blades in bright colors—Sunrise, Hot Yellow or Sunfish—behind a Rock-Runner® Bottom Bouncer. “Visibility is very poor in the summer, so you need something with a lot of thump and flash to catch a walleye’s attention,” he says. “Depending on the day, I’ll typically run from 0.8 to 1.5 mph.
And because the water’s so shallow, he recommends using side planers to take the rigs away from the boat’s path. “I usually run 3 on each side, with the inside pair 30 feet from the boat. The next set is 50 feet out and the third pair runs 90 to 100 feet from the boat.”
Trolling near the Rock River inlet is a good strategy early on, but walleyes quickly spread throughout the lake after departing the river. A solid starting point, according to Walton, is to troll the wind-blown shorelines. If it’s calm, try trolling between Carcajou Point on the north shore and Thiebeau Point to the south.
A rock pile located about mid-lake between these two points is Koshkonong’s most dominant structural feature, and it becomes a popular hotspot during the months. Include it in your trolling attack, or pitch a jig-and-leech or ’crawler over the pile. A basic float rig, however, is a simple and effective option, particularly if the wind is blowing. Try impaling a ’crawler or leech on a short-shank hook and suspend it from a Lite-Bite Slip Bobber. “Every kind of fish—walleyes, pike, crappies, perch, catfish—likes to visit the rock pile when it’s warm,” says Walton, and you might catch any one of them.”
Where the Rock River exits the lake at the south end, clam beds make up another feature that attracts walleyes. Again, because the shallowness of the water, it’s critical to keep baits away from the boat. Walton recommends allowing the boat to drift with the current while longlining a stand-up jig-and-leech (or half a ’crawler) combo.
4. Lake Koshkonong’s water temps can get so high and clarity so low, that it becomes difficult to catch fish. Many anglers simply move on to other waters at this time. Fishermen who stick it out focus on fishing areas where there are springs, river or creek inlets where fish can find cooler water.
Still others turn their attention to catfish. Channel cats average 3 pounds or so, but it’s not uncommon to catch a double-digit fish, according to Walton. He suggests looking for hard-bottom areas, where cutbait won’t sink into the muck. Put the bait on the bottom and let the fish come find it. The rock pile is one such spot, but check out any bridge you can find that features rock or rip-rap. If rock or wood cover is present, so much the better, especially earlier in the year when the fish are spawning. At that time of year, aggressive channel cats will often hit jigs and crankbaits, too.
Lake maps courtesy of Navionics. For more information, visit: Navionics.com
Size: 10,595 acres
Max Depth: 7 feet
Ave Depth: 5 feet
Species Present: Walleyes, Northern Pike, Yellow Perch, White Bass, Crappies, Bluegills, Largemouth Bass, Smallmouth Bass, Channel Catfish and Flathead Catfish.