Overview Information provided by Doug Kingsley, DNR Fisheries - Park Rapids.

 

Boards of the Big and Little Sand Lakes Associations agreed to participate in a DNR project to monitor Dissolved Oxygen (DO) and Temperature in both lakes.  The project would require measuring DO and temperature from the lakes’ surface to bottom (or as deep as can be reached) throughout the season and for several years.  The purpose is to see how those characteristics change throughout the year and from one year to the next, and to determine whether there are trends.

 

With warmer weather in recent years, we are seeing increasing water temperatures in the upper levels of our lakes during the summer.  Predictions are for that trend to continue or worsen.  In addition, land use changes may be leading to increased nutrients in our lakes, which increases oxygen consumption and decreases the amount of dissolved oxygen available for fish or other aquatic organisms, particularly in the deeper levels of lakes.  The result is smaller or inadequate portions of the lake with cool enough water and high enough DO levels to be suitable for fish like tullibee (cisco).  This is important because tullibee are an important forage fish for the lakes’ predators like walleye and northern pike, and changes in tullibee populations may affect those game fish species.  Last year (2006) was a particularly bad year where we saw summer die-offs of tullibee in several of our area lakes.  Information from this project would help us evaluate whether there are trends in DO and temperature that may be affecting fish populations like tullibee.

 

Process:

Big Sand and Little Sand lake associations agreed to collaborate with the DO/Temperature study and share the initial cost (approximately $1,600) and maintenance of the specialized probe and 100 ft. cable used for the measurements. The DNR provided volunteer training for the intricate reading and recording of the results/Readings are taken every two weeks May through October to measure available dissolved oxygen and temperatures from the surface to the bottom of the lake. The volunteer(s) anchors a boat in the deepest part of the lake to take readings every 1-3 feet of depth to determine how wide the layer of water is with the optimal DO/Temperature available for Cisco to survive.

 

Additional Information:

• Reasons for Dissolved Oxygen (DO) / Water Temperature Monitoring

• 2016 Dissolved Oxygen (DO) / Water Temperature Profile
• 2019 DO/Temp Summary and Profile

 

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