Background

To evaluate motor ability of fish, swimmill systems have been used for measurement of critical swimming speed (U_crit), which is the maximum water velocity in which fish can keep swimming. Many different swimmill equipments and protocols have been used for zebrafish studies (Table 1) and thus, it was difficult to compare results of different experiments and different protocols due to the lack of detailed calibration methods and protocols. We applied commercially available swimmill equipment Swim Tunnel Respirometer, which is the major and standard one among zebrafish researchers, established a reproducible protocol for obtaining basic swimming characteristics of adult zebrafish, such as adequate water temperature and adequate length of caudal fin among various wild-type strains (Wakamatsu et al., 2019). We here describe the detailed methods to monitor dissolved oxygen for the estimation of oxygen consumption in swimming, to measure body size of adult zebrafish, to conduct calibration of water velocity, to acclimate zebrafish to the narrow swimming chamber and to measure swimming speed. This protocol would be useful for researchers who use swimmill.
 
Table 1. Swimmill equipments. The absolute value of U_crit measured in adult wild-type zebrafish (3-12 months old) appears to vary by the difference of the swimmill equipments. This is probably due to the size difference of swimming chamber that generates uneven water flow between center and peripheral. Therefore, the comparison of U_crit should be done in the assays that use the same equipment.