AUTHORS: Daniel Paulson, Iowa State University; McKensie Vaske, Iowa State University; Michael Moore, U.S. Geological Survey, Iowa Cooperative Fish and Wildlife Research Unit; Michael Weber, Iowa State University
ABSTRACT: Alterations to natural flow regimes from hydroelectric dams, channelization, and land-use practices degrade riverine habitats for native lotic fish. For instance, over the course of multiple summers, including 2024, more than 10,000 Shovelnose Sturgeon Scaphirhynchus platorynchus have died on the Des Moines River, IA predicted to be from river alterations creating suboptimal habitat conditions. The U.S. Army Corps of Engineers through the Sustainable Rivers Program has expressed interest in restoring environmental flows and providing heat relief pulses which could improve available habitat for native lotic species. Since Shovelnose Sturgeon habitat requirements have not been studied on the Des Moines River, our objective is to quantify their habitat use and selection to determine the environmental conditions that contribute to survival during the summer months. From 2022-2024, we acoustically tagged 69 Shovelnose Sturgeon and actively tracked them 2-3 times a week from June-September 2024 (31 total events). At each fish location, we measured macrohabitat (main-channel, main-channel border, side-channel, pool, backwater, or tailwater) and microhabitat characteristics (water temperature, surface water velocity, substrate, and depth). We identified 84 Shovelnose Sturgeon locations (23 individuals; mean detections per fish = 4). These sturgeon occupied water velocities ranging from 0.23 m/s to 1.56 m/s (mean = 0.87 m/s) and water depths between 0.6 m to 3.7 m (mean = 2.01 m). Sand was the most occupied substrate (50% observations) with gravel and cobble evenly split (25% observations). We will repeat this work during 2025 to gain a better understanding of habitat use and selection on this altered river. This research could help guide management efforts on regulated rivers to promote better resiliency for downstream biota by giving insight onto what conditions are critical for Shovelnose Sturgeon during this stressful period.
