Comparisons of swimming performance in rainbow trout using constant acceleration and critical swimming speed tests

Abstract

Maximum swimming performance of seasonally acclimated rainbow trout Oncorhynchus mykiss was compared among short-duration constant acceleration tests (U max ) and with the well established, but longer duration critical swimming speed (U crit ) test. The present results show that U max was insensitive to a range of acceleration rates that differed by more than three-fold. Thus, test duration could be reduced from 58 to 18 min without affecting the estimate of U max . The value of U max , however, was up to 57% higher than U crit . Only the slowest acceleration rate tested (an increase of 1 cm s À1 every min) had a significantly lower U max , and this was up to 19% higher than U crit . Even so, the potential saving in the test duration was small (70 v. 90 min) when compared with a ramp-U crit test (a standard U crit test but with the water velocity initially ramped to c. 50% of the estimated U crit ). Therefore, swim tests that are appreciably shorter in duration than a ramp-U crit test result in U max being appreciably greater than U crit . An additional discovery was that the ramp-U crit performance of cold-acclimated rainbow trout was independent of the recovery period between tests. These results may prove useful in making comparisons among different swim test protocols and in designing swim tests that assess fish health and toxicological impacts.

Evaluation approaches of fish swimming performance

“…With regarding to the CSS, the influence of time intervals and velocity increments on its result has caught many atten-tions [22,27]. However, it still cannot draw a general conclusion on how the testing protocols will affect the final values of the CSS.…”

“…However, controversy has existed for a long time with respect to the influences of time interval and velocity increment on the CSS. Some authors demonstrated that there are no significant differences in the CSS with different protocols [27,28], while some authors found that the influence on the CSS is quite notable [29][30][31]. Also some authors argued that the influence on the CSS can be neglected within a certain range of time interval and velocity increment [7,22].…”

“…The CSS has been favored largely because it takes a shorter time to conduct and uses smaller batches of fish for a statically meaningful value [5,27,32]. However, the CSS protocol is sometimes still time consuming and is not without limitations.…”

“…To date, the Critical Swimming Speed (CSS) is the most important index to evaluate the unsteady swimming performance [23][24][25][26][27]. It is measured using incremental swimming approach.…”

“…Subsequently, the time intervals are fixed on 30 min till the fish fatigues. Farrel [27] developed the Constant Acceleration Velocity Test protocol, in which a very short time interval of 1 min duration is used. In fact, this approach can be regarded as a special case of the CSS with extreme short time interval.…”