Study

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.

Summary

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.

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