Association of Native Prey-Fish Abundance to Pallid Sturgeon Condition

An abundance decrease of selected native cyprinids (Hybognathus and Macrhybopsis spp.) has been hypothesized to be associated with the population decline of the endangered Pallid Sturgeon (Scaphirhynchus albus) because they typically become piscivorous as juveniles and adults. We assessed the relationship of body condition (relative condition: Kn) for individuals >600 mm FL to relative abundance (catch per unit effort; C/f) of native cyprinids. Using 11 years of data at three spatial scales (river section, river segment, and river bend), we found only one significant positive relationship between Hybognathus C/f and Pallid Sturgeon Kn (linear regression: p=0.01; r²=0.68); no other significant relationships were observed at other spatial scales or locations. Overall, Pallid Sturgeon mean condition was generally good (~0.90) and a general relationship of native prey-fish relative abundance to body condition was not apparent, which suggested Pallid Sturgeon were either not reliant on these native cyprinids or that these species were not limiting. Previous diet studies have shown that Pallid Sturgeon consumed other fish species (e.g., Channel Catfish and Johnny Darters) while maintaining satisfactory condition, which supports the hypothesis that they are not reliant on certain prey species, but rather can be opportunistic feeders.