The Minnesota River is a significant tributary to the Upper Mississippi River, stretching approximately 320 miles from its source at Big Stone Lake to its confluence near St. Paul. This waterway drains a vast 17,000-square-mile watershed across southern Minnesota, with portions extending into South Dakota and Iowa. The river’s unique geological history and connection to the larger Mississippi system support a remarkable diversity of aquatic life. Historically, surveys have documented over 80 fish species within the river and its tributaries, making it one of the most species-rich fish communities in the state.
Primary Game Fish Species
The Minnesota River is recognized for its robust populations of large, sought-after fish, particularly the various species of catfish. Anglers frequently target the Channel Catfish, which are common throughout the river. These catfish are often found in deep pools during the day, moving into shallow riffle areas to feed at night. They are cavity nesters, with the males guarding their eggs in secluded spots like hollow logs or under banks when water temperatures reach around 70 to 84 degrees Fahrenheit.
The river also holds a reputation for its trophy-sized Flathead Catfish, which can grow to impressive weights. Flathead Catfish prefer deep, slow-moving pools that offer dense cover, such as log jams and undercut banks. A significant portion of the Flathead population is concentrated below the Granite Falls Dam, as this structure acts as a major barrier to their upstream migration. Both species of catfish can be found side-by-side in deep wintering areas.
Walleye and Sauger are popular with anglers, providing a mixed-bag catch in the same stretches of water. Walleye populations are sustained naturally and through stocking efforts in the upstream lakes that feed the river system. The Sauger, a close relative of the Walleye, is smaller and known for its preference for the river’s murky and faster currents. Both species possess a reflective layer in their eyes, the tapetum lucidum, which gives them an advantage for hunting in the river’s often turbid water.
Essential Forage and Non-Game Fish
While game fish receive the most attention, the ecological health of the river is sustained by a wide array of less-targeted species. These non-game fish, often termed “native rough fish,” perform roles in the aquatic food web. For instance, minnows and shiners, such as the Emerald Shiner and Spotfin Shiner, are abundant and serve as a crucial food source for predatory fish like Walleye and Northern Pike.
The river system is also home to various bottom-dwelling species, including several types of Suckers and Buffalo fish. These fish, such as the Shorthead Redhorse and Bigmouth and Smallmouth Buffalo, are often commercially harvested and function as natural filters or scavengers within the ecosystem. The Common Carp is another prevalent, non-native species that lives in the Minnesota River and is frequently caught by anglers.
The Freshwater Drum, sometimes called Sheepshead, is a common fish. The presence of unique species like the Shovelnose Sturgeon, Paddlefish, and the Blue Sucker serves as an indicator of the river’s improving water quality and diversity. Many of these large river species are restricted to the downstream section of the river, unable to pass the Granite Falls Dam.
River Characteristics That Support Aquatic Life
The Minnesota River’s ability to support a diverse fishery is rooted in its unique physical and hydrological characteristics. The river is characterized by a high sediment load, which results in significant water turbidity. This murkiness, caused by high levels of total suspended solids like clay and silt, severely limits light penetration, which favors fish adapted to low-light conditions, such as the Catfish and Sauger.
This excessive sediment load, much of which comes from unstable streambanks and agricultural runoff, directly impacts the river bottom. Fine-grained sediments settle and fill the spaces between gravel and rock, a condition called embeddedness, which degrades spawning habitat for many fish. The river’s flow regime also plays a role, as increasing water flow due to land use changes accelerates bank erosion and the delivery of this sediment.
The river’s connectivity to the Mississippi River is a major factor, with the lower 240 miles remaining free-flowing, allowing for the upstream migration of many large river species. However, five dams exist on the upper reaches, with the Granite Falls Dam acting as a complete barrier to fish movement. This barrier significantly limits the distribution of at least 18 species, including Flathead Catfish and Shovelnose Sturgeon, to the lower river section.
Within the river’s geography, specific habitats are formed that sustain the fish community, including deep scour holes and shallow riffles. Backwater habitats and oxbow lakes are important, offering refuge for fish to escape the main channel’s fast currents during flood stages and serving as nursery areas for juvenile fish. The availability of cover, such as log jams and undercut banks, remains vital for cavity-nesting species like the Channel and Flathead Catfish.