Factors influencing the spatial ecology of Lake Sturgeon and Walleye within an impounded reach of the Winnipeg River

Abstract

Impoundments of free-flowing rivers for hydropower generation often confine fish to relatively small reaches that can restrict movement, limit habitat availability, and alter life history strategies. Here, acoustic telemetry was used to describe the seasonal habitat use, locomotory activity, and depth use for Lake Sturgeon (Acipenser fulvescens) and Walleye (Sander vitreus) within an impounded reach on the Winnipeg River, Manitoba, Canada. Lake Sturgeon foraged and overwintered in the riverine-lacustrine transitionary habitat as well as immediately below the tailrace of the upstream run-of-river facility. Walleye demonstrated high site fidelity to the upstream habitat situated near the tailrace of a hydropower facility. Contrary to Lake Sturgeon, that used multiple habitat types, Walleye used the tailrace for spawning, foraging, and overwintering, given their high residency rates throughout all months at this location. Activity for both species increased with water temperature and when residing in habitat types located farther upstream, but were minimally active during the winter season throughout the impounded reach. On average, Lake Sturgeon utilized 73% of the available depth while Walleye utilized 62% of the available depth across habitat types and months. Overall, the habitat located within the tailrace and below run-of-river facilities should be a conservation priority for both Lake Sturgeon and Walleye populations. There was persistent presence of Lake Sturgeon and Walleye throughout the spawning, foraging, and overwintering periods in the SSGS tailrace and within the first rkm downstream of the tailrace. The habitat proximal to run-of-river facilities generally encompasses small areas of the total potential habitat within impoundments, yet is important to both species studied here. The results provide information on the seasonal habitat use and biological responses to environmental cues for Lake Sturgeon and Walleye that will enhance management and ecological understanding for populations that are confined to impounded reaches.