Mitigating threats of aquatic invasive species in lakes requires holistic insights into the biological, physical, and chemical conditions sustaining fish communities. This study establishes important trophic baseline conditions for three key gamefish species—walleye, northern pike, and yellow perch—across 15 hardwater prairie lakes in south-central Saskatchewan, Canada, that are threatened by zebra mussel invasion. We employed stomach content analysis to evaluate diet and ontogenetic nutritional shifts in adult fishes and assessed how fish size and environmental factors influence body condition. Adult walleye transition from a diet of amphipods to fish as they grow, whereas perch and pike maintain a stable diet of invertebrates and fish, respectively. While walleye and pike decline in body condition with size, perch maintain consistently high condition. Lake productivity and alkalinity are key predictors of adult walleye and perch condition. Yet, zebra mussel invasion in hardwater lakes may not have the detrimental impacts observed elsewhere, assuming management strategies address the combined threats of invasion and climate change. These findings provide a foundation for assessing shifts in foraging ecology in yet-to-be-invaded prairie lakes.
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