I recently read the news that the lake sturgeon population is increasing in the Lake of the Woods and Rainy River system in northern Minnesota. I couldn’t help but think of the endangered pallid sturgeon here in North Dakota. They are big fish, growing to perhaps 6 feet long and weighing in at 80 pounds. Their historic range was the Yellowstone and Missouri Rivers downstream to the gulf, and upstream on the Mississippi to about Iowa.
Pallid sturgeon are large primitive bottom dwellers of large rivers, particularly where the water is turbid. They utilize a variety of habitats ranging from channels to sandbars and backwaters, but sand and gravel bottoms are often preferred. A particular female does not spawn every year, but rather every 2-3 years and would likely have migrated large distances to their spawning sites, located on deep fast water over a firm substrate. The stimulus to spawn is thought to be in response to photoperiod as well as water temperature and flow rate.
Under natural conditions the Missouri River would have had large seasonal variations in flow rates, water temperature, and other factors. Those conditions provided the various components of pallid sturgeon habitat. The historical population of pallid sturgeon on the upper Missouri is not well documented, but the species may have been occasional or somewhat common in the upper Missouri River even into the 1960’s. However the construction of mainstem dams is generally regarded as having a devastating effect on sturgeon.
Not only have the dams created barriers to their movements up and down stream, but they have also changed the wildly variable flowing river into a series of reservoirs. The casual observer may not realize it, but flowing water ecosystems such as the Missouri River are very different than lakes or reservoirs. Damming the river is thought to have also eliminated or severely reduced the conditions necessary for successful spawning. As a result, suitable spawning habitat may no longer enable the species to recover on its own.
So the reestablishment of sturgeon on the upper Missouri River can probably only be accomplished through the efforts of releasing hatchery fish. That is where the Garrison Dam National Fish Hatchery is playing an important role in restocking efforts on the Missouri River system.
If you are interested in more information on the pallid sturgeon, click here for a link to the U.S. Fish and Wildlife Service Revised Recovery Plan for Pallid Sturgeon (2014) along with the text of this Natural North Dakota.
Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.