Evaluating the use of a freshwater protected area by northern pike (Esox lucius) in a large temperate lake system

Abstract

Freshwater fish populations, especially migratory species and those with larger home ranges, are declining worldwide as a result of numerous direct and indirect anthropogenic factors. Freshwater protected areas (FPAs) are an emerging conservation tool that could help mitigate freshwater biodiversity losses by offering areas within freshwater ecosystems that provide full protection to species and the critical habitats they rely on. Using acoustic telemetry, we evaluated the use of a shallow, heavily vegetated FPA by northern pike (Esox lucius; N = 29) in a large temperate lake system in Ontario, Canada from 2019 to 2021. Receivers were deployed within the FPA, in the waters adjacent to but outside of the FPA (the “boundary area”), and throughout the open-area lake basins further from the FPA. Telemetry data revealed that 46% of fish captured and released in the FPA departed and did not return (N = 6), while the remaining 54% exhibited fidelity (N = 7). Notably, northern pike spent a significant portion of time in the boundary area, potentially because it contains deeper waters (maximum 12 m) that may offer thermal refuge or transitional space for movements to the lake’s deep main basin (max 95 m). Additionally, three northern pike that were captured and released in the lake’s main basin were detected inside the boundary area; however, their use of the FPA was minimal. Our findings underscore the importance of considering habitat requirements and movement ecology of species to inform effective FPA design and identify opportunities to enhance conservation benefits provided by these areas for mobile species.