Minnesota · Polk County

Union Lake Fishing guide

Union Lake sits in Polk County, Minnesota, and covers 888 acres, reaching 83 ft at its deepest point. Average water clarity runs about 6.9 ft. The Minnesota DNR has surveyed the lake 11 times, most recently in 2022, with walleye, largemouth bass, northern pike and bluegill in the nets.

Open the live map → Survey data

Depth to 83 ft · top 5 summer marks

Surface888 ac

Max depth83 ft

Clarity6.9 ft

Littoral44%

Surveyed2022

How to fish Union Lake through the year

Walleye

Spring: Walleye are shallow, on and just off the spawning flats and the first green weeds.
Early summer: Walleye are setting up on the outside weed edge, points and shallow structure.
Summer: Walleye are working the weed edge, points and any wind-blown structure. On a lake that drops to 83 ft, check the deep edge of that structure too.
Fall: Walleye are packing onto the sharpest breaks and points as the water cools, in big schools with short windows.

Northern pike

Spring: Pike are in the shallow bays and along new weed growth.
Early summer: Pike are on the outside weed edge and points.
Summer: Pike are on the deep weed edge and points near the coolest water they can find. On a lake that drops to 83 ft, check the deep edge of that structure too.
Fall: Pike are on the last green weeds and the breaks beside them, feeding heavily as the water drops.

Season patterns for each species. Open the live map for today's wind, light and water temp.

Size history

Biggest fish by survey year

Survey year	Walleye	Northern pike	Largemouth bass
2022	30"	34"	18"
2017	28"	32"	15"
2012	29"	30"	19"
2007	27"	30"	16"
2002	26"	33"	12"
1997	27"	32"	14"

Longest fish measured by DNR survey crews in each year's nets. Survey gear samples the population, so the lake usually holds larger fish than any survey measured.

Suggested tackle

What to bring

Top presentations for this lake's structure and clarity:

Walleye · Live bait

Live-Bait (Lindy) Rig + Leech/Crawler

jumbo leech or half a nightcrawler

8–35 ftslow

Shop octopus hooks →

Walleye · Trolling

Leadcore Line + Crankbaits

4–5" mid-diving crankbait behind a long leadcore run

15–45 fttrolling

Shop deep-diving crankbaits →

Northern pike · Soft plastics

Paddletail Swimbait on Jighead

4–5" paddletail swimbait on a ball-head swimbait jighead

3–25 ftmoderate

Shop paddletail swimbaits →

Northern pike · Muskie & pike

Soft Rubber (Bull Dawg / Medusa)

10" soft rubber body bait

3–25 ftslow

Shop musky rubber →

Largemouth bass · Soft plastics

Texas-Rigged Worm

7" ribbon-tail or straight-tail plastic worm

1–25 ftdead slow

Shop plastic worms →

Largemouth bass · Soft plastics

Wacky-Rigged Stickworm

5" stickworm

1–12 ftdead slowweedless

Shop stickworms →

Full setups, including hooks, weights and line, are on the live map. As an Amazon Associate I earn from qualifying purchases.

DNR stocking records

Stocking history

Year	Species	Stocked
2024	Walleye	591,000 fry
2022	Walleye	591,000 fry
2021	Walleye	592,000 fry
2018	Walleye	591,000 fry
2016	Walleye	591,000 fry

MN DNR · in their words

From the 2022 survey

Union Lake is an 887-acre lake located in south central Polk County. The lake has a history of large fluctuations in water levels, which are influenced primarily by ground water. The most recent water level rises in the late 1990's resulted in the formation of a lake improvement district (LID) made up of riparian owners on both Sarah and Union lakes. The LID facilitated construction of a pumped outlet to the Sand Hill River watershed, following property damage along the lake's shoreline. A standard fisheries survey was conducted in early August 2022 to assess the fish populations at Union Lake.

Following a record high abundance of Walleye in 2012, Walleye gill net catch rates have declined in recent years. However, the 2022 catch rate of 6.3 Walleye per gill net is only slightly below the lake's historical average of 6.8 per net. Lengths of sampled Walleye ranged from 7.7 to 30.1 inches with an average of 19.0 inches. The Northern Pike gill net catch rate set a record high in 2022 at 11.9 fish per net. The historic average is 6.1 fish per net. Sampled Northern Pike ranged from 15.1 to 32.0 inches with an average of 21.9 inches. About 23% of the fish sampled were over 24 inches in length.

Read the full DNR narrative

The trap net catch of Bluegill was well below average in 2022 with a catch rate of 8.3 Bluegills per net. The historical average for the lake is 36.6 per net. These fish averaged 6.0 inches in length and ranged from 3.3 to 8.4 inches. Black Crappie abundance increased slightly from recent surveys with trap nets capturing 3.6 per net. Black Crappie sampled in trap nets had an average size of 8.7 inches, but individuals up to 12.1 inches long were encountered. Gill nets caught Largemouth Bass at 1.8 fish per net. Largemouth Bass averaged 11.5 inches long, with Largemouth Bass up to 18.1 inches long measured. Yellow Perch abundance was low in 2022, with fish having an average length of 6.3 inches. Trap net catches of Common Carp were similar to past surveys, but gill nets captured a record number of fish in 2022. Other fish species sampled in 2022 included Black and Brown Bullhead, Pumpkinseed, and White Sucker.

Narrative text from the Minnesota DNR lake survey.

Recent reports

Union Lake fishing reports

Recent reports on Union Lake from guides, tournaments and regular anglers. Anything posted in the last two weeks also bumps the matching spots on the live map, so you'll see a "matches a recent report" tag on them.

Open the live map → Fished it lately? Write a report

Polk County reports

Public water access

Getting on the water

Union Lake, West (trailer launch)
Union Lake, East (carry-in)

DNR bathymetry

Union Lake depth map

Union Lake depth contour map, Polk County, Minnesota — Depth contours to 83 ft from Minnesota DNR bathymetry, free to save or print. The live map adds ranked spots and conditions on the same contours.

Within 30 miles

Nearby lakes

Sarah Lake · 366 ac · 2.3 mi
Crystal Lake · 118 ac · 2.4 mi
Cameron Lake · 225 ac · 5.3 mi
Maple Lake · 1,641 ac · 5.8 mi
Badger Lake · 256 ac · 6.4 mi
Hill River Lake · 102 ac · 13.7 mi
Store Lake · 50 ac · 16.7 mi
Sand Hill Lake · 479 ac · 16.8 mi

Quick answers

Frequently asked questions

How deep is Union Lake?

Union Lake reaches 83 ft at its deepest point; about 44% of the lake is littoral (15 ft or shallower).

How big is Union Lake?

Union Lake covers 888 acres with about 14.6 miles of shoreline.

How clear is the water in Union Lake?

DNR Secchi readings on Union Lake average 6.9 ft of visibility, middling clarity for a Minnesota lake.

What fish are in Union Lake?

Minnesota DNR surveys (most recently 2022) record walleye, largemouth bass, northern pike, bluegill, crappie, yellow perch, rock bass.

Is Union Lake stocked?

Yes. The DNR stocked walleye in 2024; the stocking table on this page lists every year back to 2016.

Does Union Lake have a public access?

Yes. Union Lake has 2 public access sites, including Union Lake, West (trailer launch).

How big do walleye get in Union Lake?

The biggest walleye measured in recent DNR surveys taped 30"; the size-history table on this page tracks the biggest fish in each survey back to 1997.

When was Union Lake last surveyed?

The Minnesota DNR last surveyed Union Lake in 2022, the most recent of 11 surveys on record.

Page updated September 22, 2026.

The live map adds today's conditions and ranked spots for Union Lake, plus a trip plan you can share:

Open Union Lake on the live map → Fished it lately? Write a report