Meeting Abstract
The lower Colorado River basin was once defined by seasonal flooding events. However, many of these waterways have been altered with the introduction of non-native fishes and hydroelectric dams. Are species which evolved in the river’s mainstem under conditions of periodic high water flows better swimmers than non-native species? We predicted that fishes native to the main stem Colorado would have a higher maximum swimming speed and lower cost of transport than introduced fishes. To test this prediction, we examined swimming capabilities of individuals of the following species: the bonytail and Colorado pikeminnow from the main stem Colorado; the roundtail chub from smaller tributaries; non-native rainbow trout and smallmouth bass. Swimming step tests were performed and depletion of dissolved oxygen was measured. The native bonytail had the highest locomotor performance, as it was able to maintain the highest sustained swimming speeds with low costs of transport. The introduced rainbow trout, which is commonly found in rivers and streams with high flow rates, had a similar metabolic rate, maximum swimming speed and cost of transport to native Colorado pikeminnow and roundtail chub. However, the introduced and invasive smallmouth bass, commonly found in pools and lakes, had the lowest maximum sustainable swimming speed and metabolic rate at all speeds. Bonytail appeared to have the “best” locomotor performance of all fishes considered here and we note their morphological similarities to high-performance swimmers from the marine environment which may assist them in coping with flooding events. As a result of anthropormorphic changes to the river, non-native fishes, even those with relatively poor swimming performance, are able to thrive in the Colorado River.
