Impacts of mute swans (Cygnus olor) on submerged aquatic vegetation in Illinois River Valley backwaters

  • Published source details Stafford J.D., Eichholz M.W. & Phillips A.C. (2012) Impacts of mute swans (Cygnus olor) on submerged aquatic vegetation in Illinois River Valley backwaters. Wetlands, 32, 851-857.


Action: Exclude wild vertebrates using physical barriers

A replicated, paired, study in 2009 in two wetlands in Illinois, USA (Stafford et al. 2012) found that excluding mute swans Cygnus olor had no significant effect on submerged macrophyte biomass after two growing seasons. Overall, the above-ground biomass of submerged macrophytes did not significantly differ between exclosures (range 1–487 g/m2) and open plots (range 2–507 g/m2). However, biomass was higher in exclosures than open plots in 13 of 18 individual comparisons (ignoring statistical significance). Methods: In spring 2008, nine pairs of 9-m2 plots were established across two shallow wetlands. Each plot was in water ≤1.5 m deep. Plots in each pair contained visually similar submerged vegetation. One plot/pair was fenced to exclude mute swans (wire mesh from 0.5–1.5 m above water surface, allowing smaller animals to pass underneath). One plot/pair was not fenced. In September 2009, submerged macrophytes were cut from five 0.25-m2 quadrats/plot, then dried and weighed.

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust