Midwest Fish & Wildlife Conference 2016

AUTHORS: Michael D. Sundberg*, Iowa State University; Ryan C. Baldwin, Iowa State University; Timothy W. Stewart, Iowa State University; Gabriel O. Demuth, Iowa State University

ABSTRACT: Landscape alterations associated with agriculture have contributed to increased fish diversity and abundance in prairie pothole region (PPR) wetlands. Invasive wetland fishes (e.g., black bullhead Ameirus melas, common carp Cyprinus carpio) may contribute to wetland degradation by increasing turbidity and reducing the abundance and diversity of indigenous organisms. In 2012, a drought resulted in declines in central Iowa PPR wetland water volume and reduced fish abundance in some systems. The objective of this study was to evaluate if reduced fish abundance resulted in changes in wetland condition. We compared several parameters indicative of wetland condition (tiger salamander Ambystoma tigrinum biomass and abundance, water clarity, plant cover and taxon richness) from 29 Iowa PPR wetlands in 2010-2011 (pre-drought) and 2014-2015 (post-drought). Pre and post-drought values were compared among wetlands where 1) large-bodied benthivorous (primarily black bullhead), pelagic (cyprinids, centrarchids), and total fish abundance was reduced, 2) where fish abundance was not reduced, and 3) where fishes were never detected. Water clarity increased across all comparisons except where fish abundance was not reduced. Plant cover increased in wetlands where large-bodied benthivorous fish abundance was reduced, likely due to reduced bioturbation. Plant taxon richness increased in all wetlands except where large-bodied benthivorous fish abundance was reduced, possibly because a few species become dominant when plant cover increased. Tiger salamander biomass increased in wetlands where total fish abundance was reduced, potentially related to increased plant cover and reduced predation. Our results suggest wetland condition generally improves following reductions in fish abundance through increases in plant cover and tiger salamander biomass. Increased water clarity across all comparisons except where fish abundance was not reduced suggests continued fish presence may have prevented water clarity from increasing. While wetlands may be negatively affected by fish, they appear to have the capacity to recover when fish abundance declines.