Northern Prairie Wildlife Research Center
In this segment the Yellowstone River's flood pulses and turbid flows largely define the Missouri River's habitat characteristics. This section contains numerous sandbars and islands, and mostly unaltered banks. The water is deeper than in either the Yellowstone or Missouri above the Confluence, and contains habitats that allow for relatively stable populations of several fish species that are in serious decline or even extirpated from many other segments of the Missouri River System.
The Erickson Island area and its riverine habitats are extremely important to the river's native fish species, especially paddlefish and the endangered pallid sturgeon. Erickson Island in the spring when turbid flows exceed the capacity of the Corp-created channel and spill into the old channel flooding the area's lowlands.
| Some of the best riverine and floodplain habitats are
found in the Erickson Island area, about 10 miles downstream from the
Confluence. The Erickson Island area superficially resembles a naturally
occurring "oxbow," with an island lying within an abandoned river bed.
The Missouri River did not naturally cut across a narrow meander loop and create Erickson Island, however. In 1957 the U.S. Army Corps of Engineers acquired fee title to land in the area by eminent domain (a portion of which was acquired from the Erickson family, hence the name), and then proceeded to dig a large trench to effectively "channelize" a portion of the Missouri River.
As a result, the Missouri River formed a new channel through the trench, leaving a long oxbow of approximately four miles of former river north of the new channel. Erickson Island is a pie-shaped interior loop created between the old and new river channels. Most excavated spoil material was deposited on the south side of the trench, and is still visible today. Although little documentation has yet been found regarding this Corps project, the main purpose apparently was to reduce the frequency and magnitude of ice jams and subsequent flooding of the surrounding area.
Although the Missouri River's lower flows are contained entirely within the new channel, under higher flow events a portion of the water naturally flows through the old river channel.
| All Corps land in this area is leased to and managed by
the North Dakota Game and Fish Department as the Erickson Island Wildlife
Management Area. Much public land in this area floods periodically. Ice
jams still occur, generally creating the highest water levels. Because
of floods, terrestrial habitat is largely aquatic or at least water-tolerant
vegetation. Thick stands of willows cover much of Erickson Island, as
well as most of the river's banks and higher islands.
Erickson Island also contains a stand of mature cottonwoods, and younger stands of cottonwood are scattered through the area. The lack of cottonwood regeneration, a serious concern in much of the Missouri River System's floodplain, does not appear to be a problem in this area.
The island supports numerous deer and other wildlife. Increasing numbers of hunters, particularly bow hunters, prowl the area each fall, since motorized vehicle travel is generally prohibited and is often impractical. An active bald eagle nest has been documented, one of only a few bald eagle nesting areas in North Dakota.
Similar south to north view of Erickson Island in late summer when it is cut off from the river and flows are contained by the new channel created by the Corps.
The most important values of the Erickson Island area are its riverine habitats. Fisheries research has documented its importance for pallid sturgeon and paddlefish, especially in fall and winter. Game and Fish adult paddlefish catch rates are higher than in any other area in the upper Missouri or Yellowstone rivers. Concentrations are, at times, likely higher in the Erickson Island area than anywhere else in their range.
The Game and Fish Department is helping conduct research to learn more about habitat characteristics that make this area so valuable. Research on other large rivers has indicated that large, woody debris provides critical habitat for many fish species. Erickson Island has many tree snags and other woody debris that toppled from actively eroding river banks. Perhaps woody debris and deeper water are important for staging and over-wintering of some fish species of concern. Or, perhaps several unique fish depend on frequent flooding of the old river channel and associated floodplain backwaters. Since the Missouri River from the Confluence downstream to near Highway 85 at Williston receives only limited seasonal angling or boating use, one of the area's assets is its remoteness.
Woody debris provides critical natural habitat for many fish species. Game and Fish netting results in the Erickson Island area document adult paddlefish catches are higher than any other area in the upper Missouri and Yellowstone rivers. Concentrations are, at times, like no place else in their range.
|Until more is known about why the Erickson Island area
appears so valuable for pallid sturgeon, paddlefish and other native fish,
it is imperative to protect it from projects that might change it. In
recent years, the Corps of Engineers has funded considerable bank stabilization
work just upstream of the area. A large irrigation project, which would
withdraw water from the Missouri River just downstream of the area, is
currently in the final planning stages.
Lake Sakakawea at full pool backs water upstream nearly to Erickson Island. Since many native species of concern, especially the endangered pallid sturgeon, show a distinct preference for riverine habitats, maintaining the level of Lake Sakakawea at lower than full pool preserves more river habitat in this area.
*Fred Ryckman is a fisheries biologist at the Game and Fish Department's Williston office.