Cody Lake is a 257 acre lake located in Rice County near the town of Wheatland. A DNR-owned public access is located on the south side of the lake off Rice County Highway 59. Cody Lake has a maximum depth of 14 feet and is placed in Lake Class 43, which includes other Waterville Area Lakes such as Circle Lake (Rice County), Crystal Lake (Blue Earth County), Gorman Lake (Le Sueur County), and Pickeral Lake (Freeborn County). It is primarily managed for Northern Pike and Yellow Perch and secondarily for Bluegill. The management plan calls for stocking Northern Pike fry 2 out of 3 years and Yellow Perch and Bluegill adults following evidence of a winterkill. Low dissolved oxygen levels recorded during the winter of 2013-2014 and results of a winterkill assessment the following spring suggest Cody Lake experienced a strong winterkill. Bluegill, Yellow Perch, and Northern Pike adults and Northern Pike fry were stocked in 2014 as a result. Cody Lake was surveyed the week of August 10, 2015 as part of a regular monitoring program conducted by the Minnesota DNR. This survey was intended to assess the fish community by deploying six gill nets and eight trap nets, as well as recording water quality parameters.
A total of 25 Northern Pike were sampled with gill nets for a catch rate of 4.2/net, indicating moderate to high numbers were present. Since 1990, catch rates have varied from 0/net in 1992 to 11.0/net in 2010 with an average of 3.7/net. Lengths ranged from 11.5 to 23.4 inches with an average of 19.6 inches. An additional 3 Northern Pike ranging from 19.8 to 23.9 inches were sampled with trap nets. All fish from both gears were 1 year old with the exception of one "young of the year" fish. Overall, the Northern Pike population in Cody Lake consists of young, fast growing fish that were likely a result of the 2014 fry stocking.
A total of 371 Yellow Perch were sampled with gill nets for a catch rate of 61.8/net, indicating high numbers were present. This was easily the highest catch rate ever recorded in Cody Lake. Since 1990, catch rates have varied from 0.2/net in 1990 to 61.8/net in 2015 with an average of 16.2/net. Lengths in 2015 ranged from 7.2 to 11.9 inches with an average of 8.6 inches. Fish from both gears were 0 to 3 years old with three year-classes present. Two year old fish accounted for approximately 72% of the sample. Much of the sample was likely fish that were stocked as adults in 2014 following the winterkill with the hope they would immediately reproduce and repopulate the lake. Although few fish were sampled from the 2014 year-class, it is possible they were not large enough to be captured by the nets at the time of the survey.
A total of 539 Bluegills were sampled with trap nets for a catch rate of 67.4/net, indicating high numbers were present. This was the most ever sampled in Cody Lake. Since 1990, catch rates have varied from 0.2/net in 2010 to 67.4/net in 2015 with an average of 15.5/net. Lengths ranged from 3.0 to 9.1 inches with an average of 4.7. Just one fish was larger than 6.0 inches. Bluegills were sampled in high numbers with gill nets as well with a total of 473 sampled for a catch rate of 78.8/net. All fish were 1 year old except for one 8 year old fish. In 2015, the Bluegill population in Cody Lake was dominated by small fish that were likely offspring of the adults stocked in 2014.
Black Bullheads were the most commonly sampled fish with gillnets in 2015. A total of 813 ranging from 4.3 to 11.1 inches were sampled for a catch rate of 135.5/net, indicating moderate to high numbers were present. Since 1990, catch rates have varied from 15.0/net in 2010 to 135.5/net in 2015 with an average of 72.8/net. Black Bullheads continue to thrive due to frequent winterkills in Cody Lake.
No Common Carp were sampled in 2015 for the first time ever. Since 1990, trap net catch rates have varied from 3.5/net in 1990 to 53.8/net in 2010 with an average of 13.4/net. It seems the 2013-2014 winterkill was strong enough to reduce the Common Carp population in Cody Lake to record lows. Unfortunately, one Common Carp was sampled the following week in connected Phelps Lake so a complete extirpation from Cody Lake is highly unlikely and Common Carp numbers will likely rebound in the absence of winterkills.
Other species sampled in 2015 include Yellow Bullhead and hybrid sunfish.
Water Quality Parameters
Water quality parameter measurements included secchi depth, water temperature, and dissolved oxygen readings. At the time of this survey, absolute secchi depth was 0.6 feet indicating poor water clarity. Water temperatures and dissolved oxygen readings throughout the water column ranged from 77.9 degrees Fahrenheit and 13.6 ppm at the surface to 75.4 degrees Fahrenheit and 0.1 ppm at 10 feet. A thermocline where dissolved oxygen fell to less than 1.0 ppm existed around 6 feet.
Anglers can play an important role in maintaining or improving a fish population by practicing selective harvest. Selective harvest allows for the harvest of smaller fish for consumption, while encouraging the release of medium to large fish that may contribute to natural recruitment. This practice helps maintain balance in the fish community and provides anglers the opportunity to catch more and larger fish in the future. Additionally, smaller fish often taste better and have fewer contaminants than larger, older fish from the same water body.
Shoreline property owners also play an important role in the overall health of an aquatic ecosystem, including the fish population. Natural shorelines, including vegetation, woody debris, and bottom substrates, provide valuable habitat for fish and wildlife, help maintain water quality, and reduce bank erosion. By leaving natural shorelines unaltered or restoring them to natural conditions, shoreline property owners are doing their part to maintain or improve a healthy ecosystem in the lake and protect the resource for future generations.
-Sky Wigen, Fisheries Specialist