Lake ecosystems

Ecological Resources collects, analyzes, and delivers vital ecological information on Minnesota lake ecosystems through a variety of programs, publications, and other resources.

Lake ecosystems questions and answers

Can I request a lake to be mapped?

Yes. Requests for lake mapping should be directed to your nearest Fisheries office.

How can I purchase a lake map?

Lake maps published by the DNR are available for purchase through Minnesota's Bookstore. You may call them at (651) 297-3000 or 1-800-657-3757.

How can I obtain a license to use DNR Lake Mapping data commercially?

Lake maps are copyrighted by the DNR. Licenses to use Lake Mapping data or to sell lake maps commercially are available for purchase through a contract agreement with the State of Minnesota. For more information, please contact Ian Chisholm at 651-259-5080.

What is a Fish Health Inspection for commercial fish hatcheries?

A fish health inspection is an on-site, statistically-based sampling in accordance with processes in the Fish Health Blue Book for all lots of fish in a facility. The inspection must include at least viral testing of ovarian fluids at the 95 percent confidence level of detecting two percent incidence of disease. Bacterial diseases must be sampled at the 95 percent confidence level with a five percent incidence of disease. The inspection must be performed by a fish health inspector in cooperation with the producer with subsequent examination of the collected tissues and fluids for the detection of certifiable disease. The cost for an inspection is $100 per lot of fish plus $25 inspection fee.

For more information, contact the Eco Services Pathology Lab.

Who needs a fish health inspection?

Any facility raising salmonids or ictalurids that has effluent discharge to public water. For more information, contact the Eco Services Pathology Lab.

Why do fish health inspections?

Minnesota has very few fish pathogens present compared to other parts of the country. Fishing is a major component of Minnesota life, in order to protect these fish stocks we need to prevent the introduction and spread of serious fish pathogens.

How do I know if a particular fish or game is safe to eat?

This is a case by case question. There is no one correct answer. The best thing to do is call and ask for assistance. For more information, contact the Eco Services Pathology Lab.

How do I send fish or game samples in for examination?

Call the fish and wildlife Pathology Lab at 651-259-5096 for instructions. Depending on what the problem may be there are different ways of preparing samples for diagnostic examination. Our ability to determine the cause of a problem is dependent upon the quality of sample received. In general we prefer samples be sent fresh, wrapped in plastic and put on ice, not frozen.

I got swimmer's itch! Where does it come from and what can I do to keep from getting it again?

The DNR has prepared this advice for avoiding or treating swimmer's itch.

How do I get rid of the green scum on my pond?

The "scum" is probably either filamentous algae or duckweed see A Guide to Aquatic Plants or see Aquatic Plants online. If you look at duckweed closely, it is composed of individual, oval-shaped plants about 1/8- to 1/4-inch in diameter. Duckweed can be removed by skimming or applying a DNR-approved herbicide. Filamentous algae is composed of long, green threads-often matted together, resembling green cotton. The "scum" could also be a severe bloom of plankton algae that has floated to the surface. Filamentous algae can be controlled with copper sulfate or other copper-based algicides. A bloom of plankton algae occurring at this stage is a sign that the algae is dying; the bloom will break up by itself.

How do I know if the green scum is a floating plant or algae?

Can it be swept aside with your hand? If it can, and it looks like green, oval seedlike plants 1/8- to 1/4-inch in diameter, it is likely duckweed. If it looks like green cornmeal, it is probably watermeal. If it cannot be swept aside with your hand and it is stringy, hairlike, or slimy or colors the water green or brown, it is likely algae.