Enhancing habitat and diversity in cattail-dominated lake shorelines across Minnesota

cattails

Researchers studied the hybrid cattail stand in northern Lake Huron. Photo credit: Brendan Nee

By Amy Schrank, Fisheries & Aquaculture Extension Educator, University of Minnesota Sea Grant Program

Nearshore aquatic plants are an important source of biodiversity in Minnesota lakes and are critical to fish communities, including important game species such as walleye, bass, pike, and sunfish, and forage fishes such as minnows and other small species essential to fish diets. Fishes using nearshore, vegetated habitat usually prefer a combination of plant forms including emergent plants such as bulrushes, floating-leaved species such as water lily, and submerged plants such as wild celery and pondweeds. This variety of plant types provides suitable substrate for fish spawning, shelter for larval and juvenile fishes to hide from predators, and habitat and food sources for other animals such as aquatic insects and crayfish that young fish depend on for food.

In Minnesota, nearshore lake communities are being altered by hybrid cattail. Hybrid cattail acts as an ecosystem engineer by replacing diverse aquatic plant communities with a more homogenous environment dominated by tall, dense, difficult-to-penetrate cattails and their leaf litter (dead cattails). Cattail is a familiar plant to anyone spending time near lakes and wetlands in Minnesota. What many people do not realize is that there are multiple species of cattail and not all are native to the region. In Minnesota, we have two species, the native broadleaf cattail (Typha latifolia) and European, narrowleaf cattail (Typha angustifolia). Where these two species overlap in range, as they do in Minnesota, they hybridize to form Typha x glauca, or hybrid cattail. Hybrid cattail tends to grow faster and taller than either parent species, and its growth produces copious leaf litter that can suppress the growth of other native plants. In addition, hybrid cattail thrives in regions with high nutrients and fluctuating water levels, both conditions that exist in lakes throughout Minnesota that have been disturbed by human changes to the landscape. Where hybrid cattail gains a foothold, the end result can be large homogenous stands of cattail where few other native plants can persist.

Though we understand how hybrid cattails affect native plants, many questions still remain. For example, how do these large stands of hybrid cattails affect the rest of the nearshore lake ecosystem including water quality and fish community? Furthermore, how can we effectively manage this ubiquitous invader? We know that herbicides are detrimental to juvenile fishes and amphibians in the aquatic environment and large-scale mechanical removal of hybrid cattails can be expensive. Are there smaller-scale options that might be feasible?

Researchers from University of Minnesota’s Sea Grant, Department of Fisheries, Wildlife, and Conservation Biology, and the Minnesota Aquatic Invasive Species Research Center (MAISRC) are embarking on a project to better understand if and how hybrid cattail removal can increase plant diversity and benefit fish communities in nearshore lake ecosystems.

The study’s objectives are to:

  • Understand the effects of hybrid cattails on nearshore lake communities (water quality, plants and fishes) across Minnesota.
  • Determine if small-scale hybrid cattail removal can increase plant biodiversity and positively affect fish abundance and diversity.
  • Compare the effects of hybrid cattail removal on nearshore lake ecosystems across the state to determine if these effects differ regionally.

Researchers are beginning their field work this summer and are currently working closely with collaborators at the Minnesota Department of Natural Resources and Voyageurs National Park to select suitable sites for the experiment. Study results will be communicated through MAISRC and University of Minnesota Sea Grant websites and researchers provide updates to lake associations throughout the state. If you are out and about on Minnesota’s lakeshores this summer, you might see our team working in the cattails; feel free to stop by, have a chat, and learn more about healthy nearshore lake communities.

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund, as recommended by the Minnesota Aquatic Invasive Species Research Center (MAISRC) and the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

PI: Amy Schrank, University of Minnesota Sea Grant

co-PI: Daniel Larkin, Department of Fisheries, Wildlife, and Conservation Biology (FWCB)

FWCB Grad students: Brendan Nee and Michael Tuma