Castle Rock Lake's Walleye Story This Fall Started in 2022. Petenwell's Is Just Beginning.

The most useful number for anyone fishing Castle Rock Lake this October comes from four years ago. In its fall 2025 recruitment survey, the Wisconsin DNR wrote that Castle Rock's 2022 year class, which produced 103 young walleye per mile when it hatched, "will recruit into the harvestable population in 2026." On the same pages, Petenwell had its best hatch since the survey began, and those fish won't reach keeper size for years. Both flowages are close to New Lisbon, but their walleye populations are running on different timelines right now. The lake's water calendar also gives you more fall to work with than most people plan for.

The hatch that counts this fall is four years old

DNR crews sampled Petenwell on Oct. 29–30, 2025, and Castle Rock on Oct. 30, 2025, with water temperatures of 50 and 51 degrees. The survey counts walleye per mile of shoreline. Its main measure is young of year, meaning fish hatched that spring. Here are the last three years against each flowage's long-run average:

Castle Rock has come in below its average three years running. Taken alone, that looks like a lake losing ground. The fish you'd keep this fall weren't hatched in any of those three years, though. They hatched in 2022, when Castle Rock put up 103 per mile, nearly double its average.

The timing fits walleye biology. According to the DNR, males mature around age three at about 11 inches, and females around age four at about 15 inches. A walleye hatched in spring 2022 turns four this year, and 15 inches is also Castle Rock's minimum length. The survey adds that young Castle Rock walleye survived better than average into their second year in 2024. That year's age-one count was 38.5 per mile against an average of 26.

Petenwell's record number is a later chapter

Petenwell's 2025 figure of 165 young walleye per mile was the highest the DNR has recorded there since the surveys started in 2015. It was also the second time in five years Petenwell topped 100 per mile. That's a big jump from 20 per mile in 2023.

The DNR expects the 2025 class to reach harvestable size "in the next 3–4 years." Counting from 2025, that points to roughly 2028 or 2029. In the meantime, Petenwell's age-one count in 2025 was 0.8 per mile, well under its average of 17. These survey numbers track young fish and are not catch reports. The DNR's summary still lays out the sequence plainly. Castle Rock has a strong class arriving this year, and Petenwell's big class is still small fish.

What "harvestable" means under Castle Rock's rules

The 2022 fish matter this fall because of where they fall within Castle Rock Lake's walleye regulations. The DNR's lake listing for walleye, sauger and hybrids reads:

• Open all year
• 15-inch minimum length
• Fish from 20 to 28 inches are protected
• Only one fish over 28 inches
• Daily bag of three

So the keeper window on Castle Rock runs from 15 to just under 20 inches, with one rare exception over 28. A class of fish growing into that range this year makes up most of what can legally go home in a cooler.

These rules come from the DNR's inland lake lookup, and the department sends anglers to separate river regulations for the Wisconsin River itself. If you fish below the dam, check the river rules first. For anyone targeting sturgeon, the DNR's 2026–2027 regulations make lake sturgeon catch-and-release on the Wisconsin River from June 6, 2026, through March 7, 2027, on the stretch from the Merrill Flowage Dam down to the Mississippi.

Where fall walleye tend to hold

J-Mata Fishing, a local guide service on these flowages, lists September and October among the best months for jigging. A Petenwell pattern guide from Omnia Fishing, updated Sept. 6, 2026, puts fall walleye along channel edges, around brush and wood where the depth changes, and on rocky drop-offs, with more feeding in low light. It suggests vertical jigging in 10 to 19 feet with a deadstick, slow live-bait rigs, and jigging over structure.

That guide was written for Petenwell. The two flowages are connected, but treat it as a starting point on Castle Rock. The spots people often name below the Castle Rock Dam and around the Buckhorn Bridge come from a Travel Wisconsin piece that presented them as spring walleye locations, not fall ones.

The water holds steady until February

Here's what stretches the season. A common assumption is that the flowages drop in fall, but Wisconsin River Power Co.'s operating rules don't allow it. Between June 15 and Feb. 1, Castle Rock's water level can move no more than one foot. Petenwell has the same one-foot limit from June 15 through Dec. 31.

The yearly flood-control drawdown follows its own schedule:

1. February: The drawdown starts, and how far it goes depends on how much water is in the snowpack up north.
2. At its deepest: Up to 6 feet at Castle Rock and up to 5 feet at Petenwell.
3. Late March: Refill usually begins with snowmelt.
4. May 1: The flowage has to be full and back at normal summer level.

Last winter started earlier than the general schedule. WRPCO began lowering Petenwell on Monday, Jan. 19, 2026, and Castle Rock on Sunday, Feb. 1, so maintenance could be done safely at the Castle Rock Dam. The company hasn't posted a schedule for winter 2026–27, so last year's dates shouldn't be read as this year's.

The drawdown matters most once there's ice. WRPCO warns that lowering a reservoir can leave the ice thin or unstable. It advises staying off the ice with snowmobiles and vehicles, obeying warning signs, horns and sirens, staying outside buoy lines, carrying a phone, and planning an escape route. Current reservoir levels are posted at wisconsinriverpower.com under "Hydroelectric Project Data."

For this fall, the takeaway is simple. The water you're fishing in October is essentially the same water you'll have in December, and the big drop won't come until after ice-up.

Lining things up before the ice

Steady water means your pier, lift and launch plans depend on the weather rather than the lake level. These are the dates and services worth knowing:

Adams County's other parks and public accesses usually close Nov. 1 unless posted otherwise, while the Petenwell and Castle Rock county parks stay open. Castle Rock Marine is open Monday and Wednesday through Friday from 9 a.m. to 5 p.m. and Saturday from 9 a.m. to 1 p.m., closed Tuesday and Sunday. It may close in winter for extreme cold or school cancellations and asks customers to call first. V2 Boat Center, The Dirty Turtle and Buckhorn Store haven't posted 2026 fall hours or closing dates, so a phone call before you tow anything will save a trip.

Living on Castle Rock or Petenwell means a lot of your year runs on dam rules, DNR surveys and shop hours. That's the kind of practical detail we pay attention to at Pfaff Properties WI. If you're thinking about what owning on one of these flowages looks like from season to season, from the fall window through the February drawdown, we're happy to talk it through. Let's Find Your Place in Wisconsin.

This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.