Along with monitoring water chemistry, staff at the Carver County Water Management Organization monitor aquatic life in lakes and streams to gauge the health of the water.

Bio-monitoring, as it’s called, includes studying freshwater mussels, aquatic bugs, and fish. In 2017, staff began surveying fish populations on lakes, completing 12 lakes thus far. Staff focus on lakes that the Department of Natural Resources does not conduct fish surveys on.

This past fall, staff began conducting fish surveys in streams. Surveying fish populations provides information on fish communities, measures the health of water and wildlife habitat, and determines the presence of invasive species.

The techniques and equipment are quite different when surveying fish in streams. Streams present different challenges, like snags that can tear nets, and the different habitats fish hang out in make them difficult to capture. To accurately and efficiently survey fish in streams, staff are using new backpack electroshocking equipment.

Electroshocking does not harm fish, it temporarily stuns them and allows staff to collect them with nets. The fish regain full normal activity in 1-3 minutes.

The electroshocking backpack works by generating an electrical circuit when the anode and cathode components are submerged into the stream. Staff follow the Minnesota Pollution Control Agency protocols and conduct the survey by waving the unit’s wand over fish habitat which can include gravel beds, overhanging vegetation, and pools. When a fish is stunned, staff use nets to collect it. Staff record the following information during each survey.

  • The time the survey was conducted.
  • Each fish species found, and the number of each species.
  • The length of the fish, including minimum and maximum lengths for each species.
  • The age of maturity. Fish are divided into two age classes: 2 years and younger, or 3 years and older.
  • Any deformities found on fish.

This fall, staff conducted fish surveys on four spots along Bevens Creek.

  • Site 1, where the creek crosses Co. Rd. 40 just south of Co. Rd. 50, had the highest fish diversity with 14 different species present and 181 fish collected.
  • Moving upstream, sites 2 and 3 are located were the creek crosses Co. Rd. 41. The north crossing, site 2, staff found 8 different species and collected 160 fish. The southern site, site 3, staff found 11 different species and collected 284 fish, the highest number of any site.
  • The furthest site upstream, site 4, located where the creek crosses Rice Ave just south of Co. Rd. 50. Staff collected 11 different species, but only 45 fish.

A total of 23 different fish species were found, including common shiners, golden shiners, green sunfish, central stoneroller, white sucker, johnny darter, black bullhead, creek chub, fathead minnow, and more. Two invasive species were found only at site 4: goldfish and common carp.

The data collected is plugged into a large algorithm called the Index of Biological Integrity. The algorithm considers the different species found, their diet, their tolerance of poor water quality, maturity, and more, and provides a score for each stream site. The scores tell us how healthy the fish populations are and provides guidance on what types of stressors might be affecting fish.

The knowledge will help the Carver County Water Management Organization manage and protect these waters.

Madeline Seveland is an education coordinator with Carver County Water Management. She can be reachedat mseveland@co.carver.mn.us.

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