Identifying factors that harm fish and other aquatic life is a key part of the watershed restoration and protection projects being carried out by the MPCA under Minnesota’s Clean Water Legacy Amendment. Similar to the MPCA’s work in streams, the Minnesota Department of Natural Resources (DNR) identifies factors that harm fish in lakes as part of its lake index of biological integrity program.
The MPCA and DNR will be working in several streams and lakes throughout Minnesota each year to gauge their health. Many waters suffer from stressors that harm fish and other aquatic life. These stressors may also affect recreation, such as swimming and fishing.
Elements of water health
The MPCA, DNR, and local partners examine several interrelated factors to identify stressors. The goal is to maintain conditions in healthy waters and fix problems in unhealthy waters.
The agencies study the following factors and relationships among them:
- Aquatic connections, such as dams, culverts, and tile drainage
- Hydrology, including stream flow and runoff
- Aquatic biology, such as fish and bugs
- Water chemistry, including oxygen levels, nutrient levels, and temperature
- Stream channel assessment, mainly erosion
- Lake shoreline assessment
What conditions stress our waters?
Too much sediment. Soil and other matter in water can make it hard for fish and other aquatic life to breathe, feed, and reproduce. Sediment can also cover spawning areas and fill in parts of streams.
Low oxygen. Aquatic life needs oxygen dissolved in the water to breathe and survive.
Temperature. Water temperature affects metabolism and the ability to get oxygen, especially for species such as trout.
Lack of habitat. Habitat affects all aspects of survival for fish and other aquatic life. Habitat encompasses places to live, food to eat, places to reproduce and means of protection.
Too many nutrients. Excess nutrients, such as phosphorus and nitrates, can be toxic to aquatic life and cause algal blooms.
Technical guidance and reports
Local partners may find this technical guidance useful for stressor identification work.
- Stressors to biological communities in Minnesota's rivers and streams (wq-ws1-27)
- Stressors to biological communities in Minnesota’s lakes (DNR)
- Stressor identification technical guidance (wq-iw1-44)
- Stressor Identification Report Template (wq-ws5-00)
- Aquatic biota stressor and best management practice selection guide (wq-ws1-26)
Stressor reports are posted on the web pages of each watershed.