True metabolizable energy of submersed aquatic vegetation in semi-permanent marshes for dabbling ducks in the upper Midwest Annual Performance Report Period: 1 July 2016–30 June 2017

Our primary objectives were to 1) estimate true metabolizable energy of common species of submersed aquatic vegetation in semi-permanent marsh habitats of the Upper Midwest for gadwall and mallards during autumns 2015–2017, and 2) use current and historic estimates of semi-permanent marsh vegetation communities during autumn within the IRV to document the net change in energetic carrying capacity for dabbling ducks and compare with habitat use by waterfowl using long-term aerial surveys of the Illinois Natural History Survey. We assayed seven species of SAV common in the Midwest that have been documented as waterfowl foods: coontail (Ceratophyllum demersum), wild celery (Vallisneria americana), Canadian waterweed (Elodea canadensis),southern naiad (Najas guadalupensis), Eurasian watermilfoil (Myriophyllum spicatum), widgeon grass (Ruppia maritima), and sago pondweed (Stuckenia pectinate; Anderson 1959, Stewart 1962, Bergman 1973, Havera 1999, Benedict and Hepp 2000, Hitchcock 2009, Baldassarre 2014). Understanding the energetic value of SAV for dabbling ducks will allow wetland managers to accurately evaluate wetland management practices and conservation planners to develop more accurate energetic carrying capacity models. We predicted that the energetic carrying capacity of semi-permanent marshes containing SAV will be slightly less than if the same wetlands were managed for moist-soil vegetation (Bowyer et al. 2005). We hypothesized that the TME of SAV per unit biomass will be less than that of moist-soil seeds and agricultural grains. Further, we hypothesized that the TME of SAV will be independent of sex and trial week.