Lake information report

Name: Upper Prior

Nearest Town: Grainwood Primary County: Scott Survey Date: 07/19/2010 Inventory Number: 70007200

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Public Access Information

Lake Characteristics

Fish Sampled for the 2010 Survey Year

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

Fish Stocking Activity

Fish Stocked by Species for the Last Ten 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

General Population

DOWID - MN DNR, Divion 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.

Dioxin
Mercury
PCBS - Polychlorinated biphenyls
PFOS - Perfluorooctane sulfanate

Status of the Fishery (as of 07/19/2010)

Upper Prior Lake is a productive, 386-acre lake located in the City of Prior Lake in Scott County. It is connected to Lower Prior Lake to the northeast via a navigable channel. The lake is primarily managed for walleye and largemouth bass. In 2009, zebra mussels were confirmed in Prior Lake. It is important that all livewells, bait buckets, and bilges be drained and all vegetation be removed from boat trailers prior to leaving the boat ramp to prevent the spread of this invasive species. A standard population assessment was conducted during July, 2010 to determine the abundance and size structure of game fish in the lake.

Walleye population abundance was moderately low (4.5/net) and similar to the 2008 assessment (5.5/net). Gill net catch was lower than the mean of 5.9/net observed over the previous five assessments (1998-2008). In 2010, 61% percent were 15 inches or larger and 11% were 20 inches or larger. In 2008, 86% were 15 inches or longer and 32% were 20 inches or longer. The proportion of larger walleye (>20 inches) in the population appeared to decrease in 2010; however, both trap net and gillnet catch revealed good survival of the stocked 2009 year class (56% of total catch). The 2007 year class had a strong presence as well (33% of total catch). Ages of walleye matched exactly years when walleye were stocked, giving no evidence for any natural reproduction. Walleye continue to be stocked on odd-numbered years. Average length and weight of walleye in the gill nets were 15.0 inches and 1.5 pounds, and the longest measured was 25.3 inches. Walleye grew fast in Upper Prior Lake, averaging 17.7 inches at age 3.

Bluegill are abundant in Upper Prior Lake. Trap net catch (62.0/net) was high; however, numbers are below the previous five-assessment average (100.9/net) and down 45% from 2008 when trap net catch was 114.0/ net. Mean length and weight of a bluegill in a trap nets was 6.9 inches and 0.26 lbs. Similar to 2008, 88% were 6 inches or larger and 2% were 8 inches or greater. Bluegill ages ranged from 2 to 9, with most (82%) ages 3 to 5. Bluegill averaged 6 inches by age 3 and 8 inches by age 6.

In the 2010 assessment, the black crappie population was lower in abundance but improved in size structure compared to 2008. Black crappie were moderately abundant in both gill nets (4.5/net) and trap nets (5.6/net). Compared to the average of the previous five assessments, abundance was 69% lower in gill nets and 73% lower in trap nets. Mean length and weight of a black crappie from trap nets was 8.3 inches and 0.32 lbs, with the largest reaching 10.3 inches. (2008: 8.0 inches and 0.27 pounds, largest was 9.1). Sixty percent of the total (GN and TN) sampled population was 8 inches or longer and 3% were 10 inches or longer (2008: 53% were 8 inches or greater and 0% were 10 inches or greater). Eighty-eight percent of the black crappie sampled were age 2 through 4, with 51% age 3. Black crappie reached 8 inches by age 3 and 10 inches by age 5.

Yellow perch abundance and size structure has remained relatively stable. Gill net catch (13.5/ net) was lower than 2008 (18.5/net), and is less than the previous five-assessment average of 20.7/net. Similar to 2008, 39% were 8 inches or larger with the largest reaching 9.8 inches. Yellow perch ages ranged from 3 to 7 with 42% age 3. Yellow perch reached 8 inches by age 4.

Passive sampling gears, such as trap nets and gill nets, are not effective methods for collecting largemouth bass, so the data presented in these nets for this species is not indicative of relative abundance. Electrofishing is the typical method for largemouth bass assessments but was not conducted during this survey. Three largemouth bass were collected in trap nets and 4 in gill nets. Average length of bass in trap nets was 14.8 inches and the longest measured 17.7 inches. A special assessment was conducted in May of 2008 to characterize the largemouth bass population in detail. In 1 hour and 15 minutes of nighttime boat electrofishing, two netters collected 81 largemouth bass at a rate of 64.8/hour. Average length and weight was 10.8 inches and 0.79 pounds, with the largest measuring 18.9 inches. Twenty-five percent of the sampled population was 12 inches or longer, and 11% were 15 inches or longer. Ages 2 through 8 were represented in the sample, 66% were age 2 through 4 and 49% were age 3.

Historically, northern pike have been found in low abundance in Upper Prior (previous five-assessment average of 1.7/gill net). This was the case in 2010, two were sampled at a rate of 0.5/gill net. Two were captured in trap nets as well. All four ranged from 19.0 to 34.5, averaging 26.3 in length.

White bass continue to increase in abundance. In 2010, we saw the highest catches on record in trap nets (1.6/net) and tied for highest in gill nets (1.0/net). At these densities, white bass are considered to be moderately abundant based on similar lakes. Fifty-six percent were 12 inches or larger and 17% were 15 inches or larger.

Other species found during the assessment were black bullhead, common carp, golden shiner, hybrid sunfish, pumpkinseed, white crappie white sucker, and yellow bullhead.

With the exception of white bass and northern pike, from 2008 to 2010 the abundance of most game fish species has shown a decline in abundance in both gill nets and trap nets. The reason for this is unknown. There was no reported winterkill on Upper Prior during the previous two seasons. There is a possibility that sampling efficiency was reduced due to environmental factors such as low summer oxygen, temperature, weather, or barometric pressure.

For more information on this lake, contact: Area Fisheries Supervisor 7050 E Hwy 101, Suite 100 Shakopee, MN 55379 Phone: (952) 496-4141 Internet: West Metro Fisheries E-Mail: MetroWest.Fisheries@state.mn.us	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 B0291 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 Internet: www.dnr.state.mn.us E-Mail: info.dnr@state.mn.us	Turn in Poachers (TIP):     Toll-free: (800) 652-9093