Fisheries Lake Survey

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Name: Pennington Mine

Nearest Town: Ironton
Primary County: Crow Wing
Survey Date: 07/12/2010
Inventory Number: 18043900

Public Access Information

Ownership Type Description
DNR Concrete West end of mine.

Lake Characteristics

Lake Area (acres): 46.68
Littoral Area (acres): 7
Maximum Depth (ft): 259
Water Clarity (ft): 29

Dominant Bottom Substrate: Sand (Abundant)
Abundance of Aquatic Plants: 16 Varieties Sampled
Maximum Depth of Plant Growth (ft): 14.0 (0-20)

Did you know? Each year, DNR fisheries personnel stock game fish fry and fingerlings in lakes lacking habitat for natural reproduction.

Fish Sampled for the 2010 Survey Year


Gear Used

Number of fish per net

Average Fish Weight (lbs)

Normal Range (lbs)


Normal Range

Black Crappie Trap net 0.67 0.5 - 2.2 0.38 0.3 - 0.5
Bluegill Trap net 54.67 7.7 - 43.4 0.09 0.1 - 0.2
Hybrid Sunfish Trap net 0.33 N/A 0.35 N/A
Largemouth Bass Trap net 1.00 0.4 - 1.5 0.05 0.2 - 0.7
Northern Pike Trap net 0.67 N/A 1.37 N/A
Gill net 1.00 2.2 - 8.7 7.04 1.5 - 3.2
Pumpkinseed Trap net 0.33 1.4 - 5.9 0.22 0.1 - 0.2
Rainbow Trout Gill net 3.00 N/A 0.50 N/A
Rock Bass Trap net 2.67 0.8 - 3.7 0.10 0.2 - 0.4
Yellow Perch Trap net 2.33 0.4 - 2.3 0.12 0.1 - 0.2
Normal Ranges represent typical catches for lakes with similar physical and chemical characteristics.

Length of Selected Species (Trapnet, Gillnet) Sampled for the 2010 Survey Year

Species Number of fish caught in each category (inches)
0-5 6-8 9-11 12-14 15-19 20-24 25-29 30+ Total
black crappie 0 1 1 0 0 0 0 0 2
bluegill 139 21 0 0 0 0 0 0 164
hybrid sunfish 0 1 0 0 0 0 0 0 1
largemouth bass 3 0 0 0 0 0 0 0 3
northern pike 0 0 0 0 1 1 1 2 5
pumpkinseed 0 1 0 0 0 0 0 0 1
rainbow trout 0 0 9 0 0 0 0 0 9
rock bass 8 0 0 0 0 0 0 0 8
yellow perch 5 2 0 0 0 0 0 0 7

For the record, the largest Longnose Sucker taken in Minnesota weighed 3 lbs., 10.6 oz. and was caught:

    Where: Brule River, Cook County
    When: 5/19/05
    Statistics: 21" length, 10.25" girth

Fish Stocking Activity

Fish Stocked by Species for the Last Ten Years

Year Species Size Number Pounds
2015 Rainbow Trout fingerlings 300 82.2
  Rainbow Trout adults 31 154.2
  Rainbow Trout yearlings 7,554 3,303.9
  Rainbow Trout yearlings 10,200 3,506.7
2014 rainbow trout yearlings 6,002 2,000.7
  rainbow trout yearlings 9,000 3,417.0
2013 Rainbow Trout yearlings 2,388 702.0
  Rainbow Trout yearlings 12,550 5,000.0
2012 Brook Trout fingerlings 4,462 512.3
  Rainbow Trout yearlings 9,357 2,619.0
  Rainbow Trout yearlings 15,464 2,060.6
2011 Rainbow Trout yearlings 15,000 4,934.2
  Rainbow Trout yearlings 1,249 387.0
2010 Rainbow Trout fingerlings 3,333 35.4
  Rainbow Trout yearlings 20,062 7,475.2
2009 Rainbow Trout yearlings 25,200 8,683.1
2008 Rainbow Trout yearlings 20,000 6,655.7
2007 Rainbow Trout yearlings 20,000 7,250.0
2006 Rainbow Trout yearlings 20,016 7,649.2

Stocking Notes
1 - indicates fish purchased and stocked by private citizens and sporting groups.
2 - indicates fish purchased by the DNR for stocking.

Stocking Fish Sizes
Fry - Newly hatched fish that are ready to be stocked usually called "swim-ups". Walleye fry are 1/3 of an inch or around 8 mm.
Fingerling - Fingerlings are one to six months old and can range from a size of one to twelve inches depending on the species. Walleye fingerlings range from three to eight inches each fall.
Yearling - Yearling fish are at least one year old. A one-year-old fish can range from three to twenty inches depending on the species. Walleye yearlings average from six to twelve inches.
Adult - Adult fish are fish that have reached maturity. Depending on the species, maturity can be reached at two years of age. Walleye reach maturity between the ages of four and six years.

Fish Consumption Guidelines

These fish consumption guidelines help people make choices about which fish to eat and how often. Following the guidelin es enables people to reduce their exposure to contaminants while still enjoying the many benefits from fish.

Pregnant Women, Women who may become pregnant and Children under age 15

County, DOWID
Species Meal Advice Contaminants
Unrestricted 1 meal/week 1 meal/month Do not eat
Crow Wing Co., 18043900
Rainbow Trout   All sizes     Mercury

General Population

County, DOWID
Species Meal Advice Contaminants
Unrestricted 1 meal/week 1 meal/month Do not eat
Crow Wing Co., 18043900
Rainbow Trout All sizes        

DOWID - MN DNR, Division of Waters' lake ID number.

Contaminants listed were measured at levels that trigger advice to limit consumption.

Listing of consumption guidelines do not imply the fish are legal to keep, MN DNR fishing regulations should be consulted.

PCBS - Polychlorinated biphenyls
PFOS - Perfluorooctane sulfanate

Status of the Fishery (as of 07/12/2010)

Pennington Mine Pit Lake is a former open pit iron mine located north of Ironton that has filled with water. Together with the connected Mahnomen Mine Pit Lake this complex is the largest mine pit lake in the Cuyuna Range with a total surface area of 320 acres. The deepest water in Pennington is over 250 ft. The water is very clear with visibility to a depth of nearly 30 ft. A concrete boat launch is located on the west end of Pennington Mine. A channel on the northeast end of Pennington connects to Mahnomen Mine. Pennington is within the Cuyuna Country State Recreation Area.

Pennington is a designated stream trout lake. Designated stream trout lakes have additional angling regulations. Be sure to consult the current Minnesota Fishing Regulations book for regulations, seasons, and possession limits before fishing designated trout waters.

A survey of the fish community and aquatic habitat in Pennington Mine Pit Lake was conducted in 2010. The fish community was assessed with 3 gill net and 3 trap nets. The total catch in the gill nets was 4 fish per set, and this was low compared to other Cuyuna mine pit lakes where average gill net catches have ranged from 2 to 63 total fish in recent surveys (median of 9.7 fish per net). Only two species were captured in the gill nets: rainbow trout and northern pike. The rainbow trout (3 per gill net) were all age-1 fish from the spring 2010 stocking of 20,062 rainbow yearlings and ranged in length from 9 to 11 inches. With an average weight at capture of 0.5 lbs, the rainbow trout did show some growth after stocking. The April 5 stocking of 10,500 yearlings had an average weight of 0.3 lbs and the May 3 stocking of 9,562 yearlings had an average weight of 0.4 lbs at stocking. Two of the northern pike captured in the gill nets were 33 inches long, and the third was 28 inches long for an average weight of 7 lbs per fish.

Bluegills were the most common fish in the trap nets with average catch of 55 per set. Bluegills ranged from 3 to 6 inches long. Rock bass were the second most abundant species in the trap nets at 2.7 per net. The catch of other species was fewer than 2 fish per trap net.

Several other fish species were found in a concurrent survey of the connected Mahnomen Mine Pit Lake that were not found in Pennington. These species included: bowfin, burbot, smallmouth bass, walleye, white sucker, and yellow bullhead. All of these species could likely be found in Pennington.

Temperature and oxygen conditions suitable for trout occurred from a depth of about 16 ft down to about 42 ft. The water was extremely clear with visibility about 30 ft. The water chemistry had low phosphorus and chlorophyll, but had fairly high ionic strength and alkalinity.

Near shore substrates were primarily sand with some gravel and cobble. Submerged trees which extend nearly to the surface are common in areas of medium depth - about 10 to 30 ft deep.

Rainbow trout were first stocked into Pennington Mine Pit in 1982. Since the early 1990's usually about 20,000 spring yearling rainbow trout have been stocked annually. Starting in 2011 Pennington is scheduled to receive 15,000 rainbow trout yearlings annually. Some of the Pennington quota has been stocked into the connected Mahnomen Mine Pit (18-0440-00) in recent years. Trout stocked in the Mahnomen complex are recorded as being stocked into Pennington.

See the Mahnomen Mine Pit Lake (18-0440-00) 2010 survey report for more survey information on this complex of mine pit lakes.

For more information on this lake, contact:

Area Fisheries Supervisor
1601 Minnesota Dr
Brainerd, MN 56401
Phone: (218) 203-4301
Internet: Brainerd Fisheries

Lake maps can be obtained from:

Minnesota Bookstore
660 Olive Street
St. Paul, MN 55155
(651) 297-3000 or (800) 657-3757
To order, use B0522 for the map-id.

For general DNR Information, contact:

DNR Information Center
500 Lafayette Road
St. Paul, MN 55155-4040
TDD: (651) 296-6157 or (888) MINNDNR

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    Toll-free: (800) 652-9093