While scientists can’t ask fish and bugs how clean the water is, they can count their numbers and species to help find that out.
From mid-June through September 2017, biological monitoring crews from the Minnesota Pollution Control Agency (MPCA) sampled a total of 921 sites in rivers, streams, and ditches across the state for fish (420 sites) and macroinvertebrates (501 sites).
Measuring and evaluating the health of fish, macroinvertebrates and plants helps to distinguish between naturally occurring variation, and changes caused by human activities.
The north biological monitoring unit sampled sites in the North Fork Crow River, Rainy River Headwaters, Rainy Lake and Rapid River watersheds. The south unit sampled in the Blue Earth, Cottonwood, Redwood, Pomme de Terre and Snake River watersheds, and surveyed a series of sites on the St. Croix River.
Throughout the summer abnormally low and high rainfall posed challenges. In the south, more than 13 inches of rain fell in the Redwood River watershed during an August storm. In northern Minnesota severe drought left streams with very little water or completely dry.
Despite the difficult conditions, crews still were able to collect good samples from a majority of locations. The south unit collected 36 species of fish in the lower reaches of the Cottonwood River, including shovelnose sturgeon, walleye and flathead catfish. One visit on the St. Croix River found 38 unique species, and many stations had greater than 30 specific groups. The north unit collected 35 fish species in the North Fork Crow River, and three other locations had more than 30 species.
Finding rare species
The south unit identified several rare species during the St. Croix River surveys, including river darter, blue sucker (special concern), gilt darter (special concern), and lake sturgeon (special concern).
The north unit found several rare species including pugnose shiner in the Otter Tail, Pine and North Fork Crow River watersheds, northern brook lamprey (special concern) in the Otter Tail and Lake of the Woods watersheds, lake sturgeon in the Little Fork watershed, and least darter (special concern) in the Pine River watershed.
While sampling lakes and streams last summer, water monitoring crews found positive signs of the Crystal Darter’s existence and reproduction.
Water quality monitoring
The MPCA’s water quality monitoring unit collected data from about 370 stream and 630 lake sampling events in the same major watersheds as well as the Rainy and St. Croix Rivers, several streams in central Minnesota, and dozens of lakes for routine condition monitoring. Local partners and citizen volunteers also helped by collecting water samples and from lakes and streams in many watersheds.
The water quality monitoring unit also participated in the National Lakes Assessment. The 150-lake random survey across Minnesota focused on determining the suitability of lakes for recreation, aquatic life and habitat.