Incorporating Fish Physiology in Stream Restoration: The Influences of Turbulence on Fish Energetics and Positional Choice

Abstract:

Habitat degradation and loss are among the factors leading to widespread declines in the abundance of freshwater fish, and instream restoration structures are frequently utilized in an effort to reverse these declines. Structures alter river flow and generate additional turbulence, but little is known about how generated turbulence impacts fish energy expenditure and habitat choice. The goal of this study was to quantify how simulated restoration structures alter turbulence and flow dynamics and how this influences fish energetics and swimming behavior. We first used accelerometers and an intermittent-flow respirometer to link energy expenditure to acceleration in two species, smallmouth bass (Micropterus dolomieu) and rainbow trout (Oncorhynchus mykiss), allowing for the estimation of oxygen consumption in different environments. We then swam implanted fish in a flume with simulated restoration structures of multiple orientations and diameters across multiple flow velocities. Flow characteristics were quantified using particle image velocimetry. When combined, these two components allowed us to develop a model that relates fish positional choice and energetic responses to turbulence. Together, this information will serve to increase the success of restoration activities by identifying the characteristics of instream restoration structures that lead to flow conditions that are energetically beneficial for fish.