Abstract

Although numerous studies have been completed on pallid sturgeon populations and behavior, few have addressed the potential for water-quality characteristics to limit recruitment and population success of pallid sturgeon. Literature on sturgeon and water-quality data indicates recruitment of pallid sturgeon may be limited by several water-quality characteristics of the lower Missouri River including:

• High summer water temperatures in excess of 30 degrees Celsius, which likely are stressful to pallid sturgeon,
• Turbidities that are more than an order of magnitude less than the unaltered Missouri River and may no longer provide adequate cover for egg, larval, and young pallid sturgeon or for older pallid sturgeon attempting to capture prey,
• Dissolved oxygen that decreases to concentrations less than 2 milligrams per liter during some river rises in the late spring and summer,
• Food webs altered by increased light availability and hypereutrophic conditions caused by or enhanced by impoundment, bank stabilization, nonnative species, and decreased allocthanous material from the basin,
• Bioaccumulative contaminants, including polychlorinated biphenyls, chlordane, dichlorodiphenyltrichloroethane (DDT) and its metabolites, mercury, and synergistic contaminant cocktails that are particularly damaging to long-lived fish, and
• Other contaminants such as agricultural chemicals (particularly atrazine) and organic wastewater compounds that can disrupt endocrine systems of fish and limit reproduction at extremely low concentrations.

Additional research could be used to characterize and quantify the requirements, tolerance, and preferences of pallid sturgeon to these water-quality characteristics, especially during the egg and larval life stages. Enhancements to existing water-sampling programs are needed to quantify the exposure of pallid sturgeon to many of these water-quality stressors.

First posted October 24, 2011