Relative Activity of Brook Trout and Walleyes in Response to Flow in a Regulated River

Abstract

AbstractCoded electromyogram telemetry transmitters were used to examine the effects of varying flows on the relative activity of brook trout Salvelinus fontinalis and walleye Sander vitreus in a regulated river. The relative activity levels of two brook trout and two walleyes were continuously monitored for a minimum of 24 h, and measurements were compared with river flow values logged at nearby gauging stations. Generally, fish relative activity levels mimicked patterns of flow change, peaks in activity level corresponding to peaks in flow. Mean relative activity was generally greatest at extreme high (≥25‐m3/s) and low (<15‐m3/s) flows. High flows may have elicited hyperactivity (increased activity) as fish sought suitable refugia, increased activity to hold position in the water column, or increased feeding activity on increased levels of drifting invertebrates. Hyperactivity at low flows may have been caused by relocation due to habitat loss or ease of movement at lower flow regimes. Physiological telemetry provides researchers with a method of quantifying the immediate effects of flow changes on fish. Increasing our knowledge of the effects of river regulation on fish is essential to the development of more effective management strategies that balance ecology and economics.