Entrainment of Pallid Sturgeon Through Floodways During the 2011 Mississippi River Flood

Three floodways along the lower Mississippi River were operated during the 2011 flood: New Madrid, Morganza, and Bonnet Carre. There was concern that the federally endangered pallid sturgeon (Scaphiryhnchus albus) would be entrained through the floodways resulting in injury or death.  Varying levels of sampling effort were conducted in each floodway to evaluate entrainment, and if sturgeon were collected, place them back into the Mississippi River.  No pallid sturgeon were collected in the New Madrid Floodway. However, 26 shovelnose sturgeon ((S. platorynchus) were collected either alive or dead.  Dead shovelnose sturgeon resulted from becoming trapped in scour holes that dried or were pumped. It was concluded that only minimal entrainment risk occurred in the New Madrid Floodway since sturgeon can exit the floodway directly back into the Mississippi River.  Neither shovelnose nor pallid sturgeon were collected in the Morganza Floodway. The relatively long distance of the Morganza Floodway from the Mississippi River reduces risk of entrainment.  A total of 20 pallid and 78 shovelnose sturgeon were collected over a 1.5-week period in the Bonnet Carre Spillway during the 2011 flood. It was demonstrated that rapid rescue of entrained pallid sturgeon can be successfully accomplished to minimize impacts to this endangered species.