Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance.

This study compared the critical swimming speed (Ucrit ) and endurance performance of three Australian freshwater fish species in different swim-test apparatus. Estimates of Ucrit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free-surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory-based measures to the design of fish passage infrastructure.