Fish composition, but not richness or abundance, differ among Phragmites, Typha, and Schoenoplectus zones during a high-water year

Phragmites australis (ssp australis) is an aggressive colony-forming species that displaces emergent vegetation in North America, including native bulrushes (Schoenoplectus sp.) and both native and invasive cattails (Typha sp.). Phragmites expansion can alter habitat and negatively affect reptiles, amphibians, and birds; less is known about Phragmites’ utility as fish habitat and its impact on fish communities in freshwater coastal wetlands. To assess fish use of Phragmites in summer, we compared habitat characteristics, water quality, and fish community composition, diversity, and abundance among stands of flooded Phragmites, Typha, and Schoenoplectus at 16 sites across four regions of the Laurentian Great Lakes. Despite marked differences in water quality (higher pH and morning dissolved oxygen in Schoenoplectus) and habitat characteristics (higher stem density in Phragmites), there were no significant differences in fish species richness or catch per unit effort among vegetation types; there was a distinct fish assemblage in Schoenoplectus (more Cyprinids) compared to both Phragmites and Typha (more Centrarchids). This suggests that expansion of Phragmites or Typha at the expense of Schoenoplectus may alter wetland fish assemblages; however, with no clear differences in other fish community metrics, flooded Phragmites may provide habitat for some fishes during the summer, in the study wetlands.