Estimating the abundance and biomass of common carp in Cedar Lake and developing a sustainable management strategy for carp using integrated pest management strategies

Estimating the abundance and biomass of common carp in Cedar Lake and developing a sustainable management strategy for carp using integrated pest management strategies

2017-05-01

Cedar Lake is a relatively shallow and productive lake in Scott County, Minnesota, and like many systems in the region could be susceptible to the impact of the common carp. The common carp (or ‘carp’) can have severe impacts on water quality in lakes due to their tendency to root in lake sediments while searching for food, which releases sediment-bound nutrients into the water column, increases sediment re-suspension and creates favorable conditions for algal blooms. The carp can also uproot aquatic vegetation, which destabilizes lake ecosystems even more. Research shows that the impacts of carp on lakes are biomass-dependent. Several whole-lake manipulations suggest that carp are not damaging to lake ecosystems as long as their biomass does not exceed 100 kg/ha (Bajer et al. 2009). This value is commonly used as a management goal in carp management efforts. Unfortunately, in many lakes in south-central Minnesota, carp biomass commonly reaches 300-500 kg/ha (Bajer and Sorensen 2012). Reports on carp density in Cedar Lake are somewhat conflicting. Electrofishing surveys conducted by St Mary’s University indicated low densities of carp. In addition, informal reconnaissance on the lake by Carps Solutions on two occasions in 2015 suggested that carp may not be at densities above the threshold of 100 kg/ha. Typically, high densities of carp (> 100 kg/ha) are associated with very low abundance of rooted aquatic vegetation in lakes, and the fact that much of Cedar Lake is at times covered by curlyleaf pondweed suggested that carp biomass might be lower than 100 kg/ha. However, the 2011 TMDL assessment suggested that carp biomass in Cedar Lake might be significantly higher (approximately 400 pounds/acre), based on the estimates of internal phosphorous loading. Further, carp bow-fishing tournaments conducted each spring result in capturing numerous large carp. It was important for Scott WMO to determine the biomass of carp in Cedar Lake to facilitate further efforts to improve water quality in this lake in a cost-effective manner. It was also necessary to determine whether carp, or other processes, are responsible for the high internal loading of phosphorus suggested by the 2011 TMDL report. In this report, we summarized our results to address four objectives: 1) Develop a population/biomass estimate for carp in Cedar Lake 2) Assess spatial use of Cedar Lake by carp to identify areas where they aggregate and may be vulnerable to removal 3) Assess the age structure of carp in Cedar Lake to determine recruitment history 4) Recommend goals/strategies to reduce carp biomass in Cedar Lake to a level that will protect habitat and improve water quality.

Scott Watershed Management Organization

15

Water Biology & Aquatic Habitat
Water Monitoring & Assessment
Surface Water

Pest management
Carp usage

vedar Lake

Scott

2010-2019

No

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