Bertha Lake Fishing Guide: What the DNR Survey Shows
Bertha is a deep, clear bowl on the southwest end of the Whitefish Chain, and the state's own nets say its predators run large.
Some lakes reveal themselves slowly. Bertha Lake is one of them. At 337 acres it is modest in size, but it drops to 64 feet, and that depth shapes nearly everything about how it fishes. Cold, oxygen-rich water down deep holds tullibee and lake whitefish, and those forage fish feed the walleye and northern pike that anglers come for.
This guide leans on the Minnesota DNR's own survey work, so you can plan your season from what the nets found rather than from dock talk.
Thinking about a place of your own on Bertha? Start with the buyer's page, or read the full Bertha Lake guide.
What the 2024 DNR survey found
The DNR completed a standard fish survey on Bertha Lake in June 2024, its most recent full survey. Earlier standard work dates back to 1990, with additional surveys in 1995, 2000, 2005, 2011 and 2018, and targeted nearshore surveys in 2018 and 2022.
- Walleye. Gill nets caught 1.4 walleye per net, which the DNR rated as average. The fish were big: they averaged 24.4 inches, and the largest measured 28.4 inches.
- Northern pike. The catch was 8.6 per gill net, close to the 7.9 per net seen in 2018. Twenty-nine percent of the pike sampled were 26 inches or longer.
- Largemouth bass. Night electrofishing across stations on the Whitefish Chain averaged 44.9 bass per hour. Bass averaged 13.1 inches, 65 percent were over 12 inches, and the largest was 19.2 inches.
- Smallmouth bass. Three were caught during electrofishing, all over 16 inches.
- Bluegill. Trap nets averaged 26 bluegill per net, an average number. Size was the weak spot: they averaged 5.2 inches, and only 8 percent reached 7 inches.
- Black crappie. Numbers were low in both net types, though most fish caught were 8 inches or longer.
- Tullibee (cisco). The gill net catch was 6.2 per net, down from 14.8 in 2018.
Other species in the 2024 nets included yellow perch, rock bass, pumpkinseed, hybrid sunfish, bowfin, lake whitefish and several bullhead species.
A healthy fish community
The DNR's 2018 nearshore survey recorded 22 native species, including nine considered intolerant of pollution, and described the lake's fish-based index score as exceptionally high. A follow-up nearshore survey in 2022 concluded that the fish community in Bertha Lake is healthy. A 2023 temperature and oxygen profile found cold, oxygenated water suitable for lake whitefish and cisco, the deep-water fish that need it most.
Walleye are not stocked directly into Bertha. The DNR stocks the Whitefish Chain with walleye fry every year and fingerlings every other year, and walleye move freely between connected lakes.
Reading the water
The DNR's 2011 vegetation survey mapped Bertha as an oval basin with several small bays joined to the main lake by narrow channels. The main lake bottom is mostly hard: sand, gravel and rubble. The two southern bays and the east bay are softer, with muck and silt. Plants grew to about 21 feet, and almost all plant species were found in water 10 feet or shallower. Waterlily beds and some wild rice sit mostly in the shallow southern and eastern bays.
That layout gives you a simple seasonal map:
- Spring. Soft-bottom bays warm first. Look for pike and panfish along the weed edges as plants come up.
- Summer. Walleye and pike follow the deep weed line and the drop-offs from the hard-bottom flats. Bass hold on the shallow cover.
- Fall. As the water cools, predators push back toward the breaks and feed heavily before ice.
- Winter. Deep basins and the edges of the flats are the usual starting points for walleye and pike through the ice.
Access and launch
Bertha Lake has no public boat launch of its own. The DNR lists two ways in, both open to the public: by channel from Whitefish Lake to the north and by channel from Clamshell Lake to the east. Clamshell has a U.S. Army Corps of Engineers public access, which makes it a common starting point for anglers headed to Bertha.
Rules worth knowing
The Whitefish Chain, including Bertha and Clamshell, carries a special sunfish daily limit of five. The DNR has also designated Bertha as infested with zebra mussels, so clean plants and animals off your boat and trailer and drain all water, including bilges, livewells and bait buckets, before you leave. Check the current Minnesota fishing regulations before each season, since special rules can change.
Questions
Are there big walleye in Bertha Lake?
The 2024 DNR survey found walleye that averaged 24.4 inches, with the largest at 28.4 inches. Numbers were average for similar lakes, so expect fewer fish but good size.
Can I launch a boat directly on Bertha Lake?
No. Bertha has no public launch of its own. Boats reach it by channel from Whitefish Lake or from Clamshell Lake, which has a public Army Corps of Engineers access.
Is Bertha Lake stocked?
Not directly. The DNR stocks walleye into the Whitefish Chain, and those fish move into Bertha through the connecting channels.
Keep reading
See what it is like to live on Bertha Lake, follow a year on Bertha, or browse every lake on the Whitefish Chain.
Have questions about fishing, lake homes or what a property on Bertha is worth? I am David Olson, a broker with a family cabin on the Whitefish Chain in Crosslake. Call or text 218.513.2677 or email david@whitefishpropertyfinder.com. Buyers can start on the buyer's page.
Sources: MN DNR LakeFinder fish survey data, Bertha Lake; MN DNR aquatic vegetation report, Bertha Lake (2011 survey); MN DNR experimental and special management waters.