Dissolved Oxygen Monitoring

The West Metro Area Fisheries office monitors dissolved oxygen (DO) levels in several lakes during winters. Testing is focused on publicly accessible waters that are: 1) marginal fish lakes with a history of fish die-offs/winterkill, 2) gamefish lakes with permitted, operable aeration systems, and 3) special fish-management situations.  Others, such as permitted aeration system operators, sometimes do their own oxygen testing.

Taking DO-level profiles allows us to assess aeration effectiveness and alerts us to potential winterkill conditions.  In most cases, we begin monitoring once ice is firmly established-- typically by mid-January. Our sampling usually stops when we see either oxygen levels stablizing near their lowest levels or winterkill indicators; other permittees/cooperators might continue taking readings.  Most sampled lakes are visited 1-3 times per winter.

We use a portable electronic meter to measure oxygen concentrations (unit of measure:  parts per million [ppm], equivalent to milligrams per liter [mg/l]).  Readings are taken from just below ice to the bottom (typically at 2-foot intervals).  Gamefish populations usually withstand DO levels above 2 ppm. 

Local Lakes Opened To Liberalized Fishing: NONE PRESENTLY.  More information on liberalized fishing and list of opened lakes statewide can be found here.

Last updated:  February 24, 2015

Notes: Data are informational only and should not be considered complete or "official."  Winterkill might not occur despite low oxygen readings, or be limited in scope ("partial winterkill").  Fish die-off confirmation and detailed impacts on populations require observation and perhaps extra sampling.

Go to  Hennepin County   Scott County

Carver County

Oxygen readings at surface/mid-depth/bottom; winterkill potential high when values are persistently below 2 ppm

Lake / Test Depth Jan 15-31 Feb 1-15 Feb 16-28 March 1-31

Courthouse     15 ft

15.1  11.7  10.3  17.7   9.5    5.3    

                       55 ft

 17.0  10.3  1.9 12.9    7.2    0.4    
         

 Eagle               12 ft

   3.4     2     0.2    

 Lucy                14 ft

  3.1    1.3    0.2    

Susan               14 ft

  4.6     2     0.2    

Susan c            16 ft

9    1.4    0.1 6    2.3    0.2 2.8   2.2   0.2  

 Virginia           30  ft

   11.4   0.6    0.1    

 Hydes              14 ft

   7.3   6.4    1.5    

 Swede               9 ft

   7.9    2.6    4.7    

 

       

* lake with operating aerator      C cooperator/permittee data

 

Hennepin County

Oxygen readings at surface/mid-depth/bottom; winterkill potential high when values are persistently below 2 ppm

Lake / Test Depth Jan 15-31 Feb 1-15 Feb 16-28 Mar 1-31

Red Rock          16 ft

     7.5   4.3   0.2  

Starring            13 ft

     13.6   2.7   0.2  

 Duck                  6 ft

     6.2   5.9   4.5  

 Mitchell            13 ft

     11.5   9.7    8.4  

 Snelling             5 ft

     4.9    4.7    2.4  

Lower Penn        3 ft

    13.2     12.2  


       


       

 

       

 

       

* lake with operating aerator      C cooperator/permittee data

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Scott County

Oxygen readings at surface/mid-depth/bottom; winterkill potential high when values are persistently below 2 ppm

Lake / Test Depth Jan 15-31 Feb 1-15 Feb 16-28 Mar 1-31

Cedar                      10 ft

   18       10      2    

Cynthia                      7 ft

  15      9.5     0.7    

McMahon (Carls)     16 ft

   7.3     6.2     4.7    

 O'Dowd                  22 ft

  5.2      5      3.4    

 St. Catherines           6 ft

   9      6.5      4.6    

 Thole                     12  ft

   7.9     6.7     3.3    


       

 

       

       


       

* lake with operating aerator     C cooperator/permittee data

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