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:  January 16, 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   aerated before ice-up

                          55 ft

 17.0   10.3   1.9      
         
         

 

       

       

 

       

 

       

 

       

 

       

* 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


       


       

 

       

 

       

 

       


       

 

       


       


       


       

 

       

 

       

* 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

 

       


       


       

 

       

 

       

 

       


       

 

       

       


       

* lake with operating aerator     C cooperator/permittee data

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