Comparative physiology and relative swimming performance of three redhorse (Moxostoma spp.) species: associations with fishway passage success

Abstract

Our understanding of biological design criteria to facilitate fishway passage design is limited, partially due to the lack of understanding of biological motivators, cues and constraints, as well as a lack of biological performance evaluations of structures once they are built. The Vianney-Legendre vertical slot fishway on the Richelieu River, Quebec, passes large numbers of migrating redhorse (Moxostoma spp.) upriver to spawning grounds each year. We evaluated the physiological capacity and relative swimming ability of three redhorse species (M. anisurum, M. carinatum, M. macrolepidotum, silver, river and shorthead redhorse respectively) to determine how these biotic factors relate to variation in fishway passage success and duration. Shorthead redhorse had higher maximum metabolic rates and were faster swimmers than silver and river redhorse. River redhorse recovered their lactate and glucose concentrations more quickly than silver and shorthead redhorse, and river redhorse were second in terms of metabolic recovery and swim speed. Additionally, fish sampled from the top of the fishway had nearly identical lactate, glucose and pH values compared to control fish. Using passive integrated transponders in 2010 and 2012 we observed that passage success and duration was highly variable among redhorse species and was not consistent among years suggesting that other factors such as water temperature, timing of the study and river flows modulate passage success. Clearly additional research is needed to understand how organismal performance, environmental conditions, and other factors (including abundance of conspecifics and other co-migrants) interact with fishway design features to dictate which fish will be successful and to inform design of future fishways. Our research suggests that there may be an opportunity for a rapid assessment approach where manual chasing and sampling of fish from the top of the fishway are used to determine which species (or sizes of fish) are exceeding their physiological capacity during passage.