Effects of season, habitat characteristics, and water levels on fish assemblages in coastal wetlands

Session: Great Lakes Coastal Wetlands: Innovative Research to Improve Restoration (4)

Matthew Windle, The St Lawrence River Institute of Environmental Sciences, [email protected]
Kate Schwartz, St. Lawrence River Institute, [email protected]
Jeff Ridal, St. Lawrence River Institute of Environmental Sciences, [email protected]

Abstract

In 2017 the Upper St. Lawrence River entered a new era of water level and flow regulation with the implementation of the International Joint Commission’s Plan 2014.  The plan is designed to allow for more natural variations in water levels, with a primary goal of improving the health and diversity of coastal wetland ecosystems.  Here we examine seasonal and spatial trends in fish assemblages of these coastal wetlands along a 200 km length of the Upper St. Lawrence River, using nearshore seining survey data of 80,000 fish documented from 2016-2018.  We compare fish species composition, diversity, richness, and abundance among sites, and relate these trends to physical habitat characteristics, water quality, water levels, and shoreline morphology.  Our study provides insights into differences among fluvial sections of the river and how these assemblages may respond to a more naturalized water level regime.