Distribution of Fishes in the Red River of the North Basin on Multivariate Environmental Gradients

Physical Characteristics of the Red River Basin

A review of the physical and environmental characteristics of the Red River is required to fully understand factors controlling the distribution patterns of fishes in the basin. The Red River is a northward-flowing river formed by the confluence of the Otter Tail and Bois de Sioux Rivers at the neighboring cities of Wahpeton, North Dakota, and Breckenridge, Minnesota. The Red River forms the boundary between North Dakota and Minnesota as it meanders for 394 river miles (mi) to the international border at Manitoba, Canada (Figure 1) (Tornes and Brigham 1994). The straight-line distance from the origin of the Red River to Manitoba is 186 mi. In Manitoba, the Red River joins with the Assiniboine River at Winnipeg and then drains into Lake Winnipeg at its southern end. Waters from Lake Winnipeg eventually flow into Hudson Bay; thus, the Red River is a portion of the Hudson Bay drainage system.

Figure 1. Location of the Red River of the North basin in the United States.

Tributaries

The Red River is joined by several major tributaries as it flows toward the Canadian border. Streams flowing from the west include the Wild Rice, Sheyenne, Elm, Goose, Turtle, Forest, Park, and Pembina Rivers in North Dakota (Figure 2). Streams flowing from the east include the Buffalo, Wild Rice, Sandhill, Red Lake, Snake, Tamarac, Two, and Roseau Rivers in Minnesota. Note that there are two major tributaries with the name Wild Rice, a potential source of confusion.

Figure 2. Major streams in the Red River of the North basin.

Drainage basin

The Red River drainage basin in the United States encompasses a total of 39,199 mi², which includes 20,820 mi² in North Dakota, 17,806 mi² in Minnesota, and 573 mi² in South Dakota (U.S. Army Corps of Engineers 1980) (Figure 1). Continental glaciers deposited between 150 to 300 ft of materials over the basin, shaping a broad, flat lake plain at its center surrounded by rolling uplands, wetlands, and lakes along the western and eastern margins. The fertile, productive soils and flat landscape have resulted in 66% of the total basin land area being used as cropland and 8% as pasture and rangeland (Stoner et al. 1993). Forests, open water, and wetlands comprise the remaining 26% of the land area. Beach ridges and deltas of glacial Lake Agassiz (Teller and Bluemle 1983) lie at the transition zone between the flat lake plain and the upland areas that were not water covered. The most extreme transition occurs in the northwestern basin, where the Pembina Escarpment rises 600 ft from the lake plain and forms an area of rolling hills (U.S. Army Corps of Engineers 1980). Stream slopes range from 2-5 ft/mi in upland areas to about 1-1.6 ft/mi in the lake plain (Stoner et al. 1993).

The Red River basin is bordered by the James River basin (Missouri River) and the Devils Lake closed basin to the west, the Minnesota River basin to the south, and the Mississippi and Rainy River basins to the east. Several of the headwaters of the Otter Tail, Wild Rice, and Red Lake Rivers in the eastern portions of the Red River basin are in close geographic proximity to those of the Mississippi River, whereas streams in the western portions of the Red River basin are more distant from streams of neighboring drainage basins.

Ecoregions

Portions of five ecoregions (Omernik and Gallant 1988) lie within the Red River basin. The ecoregions are, from west to east with percent of basin land area covered, the Northern Glaciated Plains (NGP) (31%), Red River Valley (RRV) (46%), North Central Hardwood Forest (NCH) (10%), Northern Lakes and Forests (NLF) (3%), and Northern Minnesota Wetlands (NMW) (10%) (Stoner et al. 1993) (Figure 3). Only a small portion of a sixth ecoregion, the Northwestern Glaciated Plains, occurs in the extreme western Red River basin near the headwaters of the Sheyenne River; and for this study, it will be grouped with the NGP.

Figure 3. Ecoregions in the Red River of the North basin.

The NGP is a region of rolling hills through several moraines and has numerous prairie pothole wetlands (Omernik and Gallant 1988). The Sheyenne River is the major river in the NGP, and most (90%) of the first- and second-order streams (Kuehne 1962) are ephemeral (Stoner et al. 1993). Habitat characteristics of NGP streams range from rocks and gravel in moraine reaches to sand, silt, and organic matter in pools, backwaters, and meanders.

The RRV occupies the basin of glacial Lake Agassiz and is nearly level as land altitude changes only 350 ft from Wahpeton, North Dakota, to the Canadian border. The region has been altered by numerous drainage ditches and flood control structures, and nearly all of the land in the region is agricultural (Stoner et al. 1993). Typical habitats in the RRV include runs and bends with substrates of sand, clay, and silt and abundant woody debris.

The NCH contains both hilly areas and small plains, with the varied terrain supporting forests and woodlands, croplands, dairy farming, and poultry production (Omernik and Gallant 1988). Major streams in this region include the Otter Tail, Pelican, and Buffalo Rivers. The NCH has an extremely high density of lakes; and streams tend to be high in gradient with substrates of gravel, sand, and rock (Stoner et al. 1993). Riffles, runs, and pools are abundant, and habitat diversity is high.

The NLF is characterized by a topography of steep rolling hills mixed with bogs, wetlands, and lakes (Omernik and Gallant 1988). Most of the region is ungrazed forest and woodland, and some is used for timber production. Nutrient-poor soils preclude most agriculture. Streams of the NLF include the headwaters of the Otter Tail, Wild Rice, and Clearwater Rivers. Between lakes, the streams are of moderate gradient and contain a diverse community of aquatic macrophytes and riparian vegetation (Stoner et al. 1993).

The NMW is covered by swamp, peat bogs, and boreal forest vegetation and has been described as a "vast and nearly level, sparsely populated marsh" (Omernik and Gallant 1988). The region includes the Upper and Lower Red Lakes, and streams include the Roseau River and portions of the Red Lake River, including those draining into the Red Lakes. Although numerous drainage ditches have been constructed in the watersheds, the streams of the NMW have been considered the least disturbed aquatic environments within the Red River basin (Stoner et al. 1993).

Environmental gradients

The extensive variation in topography, soil types, land use, riparian conditions, and presence of lakes and other wetlands has resulted in a wide range of streamflow and water quality conditions which could potentially have an effect on the distribution of fishes in the Red River basin. The basin is at the eastern margin of a large rainshadow caused by the mountains of western states. The mean annual precipitation increases from 17 in in the west to 26 in in the east, while the mean annual net evaporation increases from 4 in in the east to 22 in in the west (Stoner et al. 1993). Therefore, the Red River receives most of its flow from eastern tributaries. The mean annual runoff (the depth to which the drainage area would be covered if all the runoff for the year were uniformly distributed on it) in North Dakota ranges from 0.49 in for the Wild Rice River at Abercrombie to 1.34 in for the Park River at Grafton. In Minnesota, mean annual runoff ranges from 2.03 in for the Buffalo River near Dilworth to 4.07 in for the Red Lake River at High Landing.

Flow variability also differs greatly across the Red River basin. The coefficient of variation (CV) of mean annual streamflow decreases roughly from southwest to northeast (Stoner et al. 1993). The CV of mean annual streamflow is 113% for the Bois de Sioux River near White Rock, South Dakota, and is 41% for the Otter Tail River near Fergus Falls, Minnesota. Historically, the lowest flow variability has occurred in the Otter Tail River and in the headwaters of the Red Lake River near High Landing, Minnesota.

Along with different streamflows, there is great variability in the specific conductance, nutrient levels, suspended sediments, and pesticides at sites throughout the Red River basin (Tornes and Brigham 1994). In general, specific conductance is highest in western tributaries and lowest in eastern tributaries. A "salt lake" is associated with the Park River near Grafton.

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