Effects of river stage height and water temperature on diet composition of year-0 sturgeon (Scaphirhynchus spp.): a multi-year study

The diet composition was quantified of year-0 Scaphirhynchus sturgeons during sampling years (2004-2008) from the Middle Mississippi River to evaluate trends in diet. River stage height varied among years and seasons. Water temperature differed among seasons but did not differ among years. The presence of empty stomachs was evident across years, seasons, and size classes of sturgeon. The overall Multivariate Analysis of Variance for frequency of occurrence was significant, suggesting that macroinvertebrate taxa (e.g. Ephemeroptera, Diptera pupae, Chironomidae, Other) differed among size classes of sturgeon, but not seasons or years. Furthermore, Tukey's pairwise comparisons indicated Ephemeroptera frequency of occurrence differed between medium and large size classes; Diptera pupae differed between small and medium size classes and small and large size classes; Chironomidae differed between small and large size classes and medium and large size classes; the macroinvertebrate taxa category Other differed between small and large size classes. Ultimately, because of the link between diet and growth of year-0 Scaphirhynchus sturgeon, the early life history may affect eventual recruitment to adult stages.