Swimming performance of upstream migrant fishes: New methods, new perspectives

The ability to traverse barriers of high water velocity limits the distributions of many diadromous and other migratory fish species, and is central to effective fishway design. This dissertation provides a detailed analysis of volitional sprinting behavior of six migratory fish species (American shad Alosa sapidissima, alewife A. pseudoharengus, blueback herring A. aestivalis, striped bass Morone saxatilis , walleye Stizostedion vitreum, and white sucker Catostomus commersoni), against controlled water velocities of 1.5–4.5 m · s−1 in a large, open-channel flume. In Chapter 1, I develop models of maximum distance traversed ( Dmax) by fish ascending these flows, accounting for water velocity and other covariate effects. I then demonstrate the application of these models, using them to predict proportions of active migrants capable of traversing a range of distances and flow velocities. Chapter 2 focuses on behavior and swimming performance of American shad, analyzing covariate effects on attempt rate as well as Dmax, and formalizing how rate and distance jointly affect overall rates of passage. Models describe a complex pattern of varying responses of attempt rate and Dmax to hydraulics, temperature, effort expended on and recovery time since the previous attempt. In Chapter 3, I use the effect of swimming speed on fatigue time to calculate an optimal swimming speed that maximizes the over-ground distance fish can traverse, and hence defines their maximum ability to traverse velocity barriers. This speed reduces to a constant groundspeed within a given gait, regardless of the speed of flow. Data from all six species support this view, although only American shad exhibit a clear shift from the optimum prolonged speed to the optimum sprint speed at the predicted critical flow velocity. Throughout this dissertation I make extensive and novel use of statistical techniques developed for survival analysis to analyze and model behavioral data, both with respect to attempt rate and to D max. Chapter 4 provides an overview of these methods and demonstrates their application to a fish passage study of downstream-migrating Atlantic salmon (Salmo salar) smolts. An understanding of the principles described here will help the reader to better understand the findings of the previous three chapters.