Documenting Water Depth Fluctuation and Waterfowl Occurrence within Wild Rice Beds in the St. Louis River Estuary

Abstract

The St. Louis River Estuary’s shallow wetlands are home to northern wild rice (manoomin), an ecologically, economically, and culturally important keystone species. Wild rice abundance in the Estuary was negatively impacted by pollution and other human activities following the arrival of European settlers. Unfortunately, despite water quality improvements, habitat restoration, and seeding efforts, wild rice beds have not fully recovered to their previous distribution and density. This is likely due to several factors, including fluctuating water depth and herbivory by waterfowl. We documented water depth fluctuations and waterfowl occurrence in four sheltered bays during the 2020 growing season to help support future restoration decisions in the Estuary. Our observations show that estuary wild rice beds experienced 24-hour water depth fluctuations between 0.64 and 0.95 ft on average. Allouez Bay experienced the most extreme water depth fluctuations with a maximum of 2.1 ft in a 24-hour period. We documented much higher waterfowl occurrence, especially Canada goose presence, in Duck Hunter Bay South. Abundances were highest in mid-September indicating high levels of herbivory on maturing rice. We show some distinct differences in water depth fluctuations and waterfowl occurrences among sites and therefore preliminarily suggest differentially targeting seeding and goose management practices among wild rice beds as an initial management strategy.