No difference between critical and sprint swimming speeds for two galaxiid species

Researchers have used laboratory experiments to examine how fish might be affected by anthropogenic alterations and conclude how best to adjust fish passage and culvert remediation designs in response. A common way to document swimming performance for this purpose is measuring fish critical swimming speed (U_crit ). Nonetheless, the U_crit protocol as defined by Brett [(1964) Journal of the Fisheries Research Board of Canada, 21, 1183-1226] may be inappropriate for studying swimming performance and determining how it relates to upstream migration in benthic fish, as they may not actively swim throughout the entire U_crit test. An alternative method to estimate swimming performance is sprint swimming speed (U_sprint ), which is suggested to be a measure of the burst speed of fish rather than maximum sustained swimming speed. The authors conducted comparative swimming performance experiments to evaluate whether U_sprint can be used to compare swimming performance of benthic species to that of pelagic, actively swimming species. They measured individual swimming speeds of īnanga (Galaxias maculatus), an actively swimming pelagic species, and banded kōkopu (Galaxias fasciatus), a fish that exhibits benthic station-holding behaviour, using both the U_sprint and U_crit test. Experiments revealed that no significant statistical difference between swimming speeds was estimated using the U_crit and U_sprint test protocols for both G. maculatus and G. fasciatus. The result of this study suggests that fish swimming speeds obtained using these two methods are comparable for the species used in this study. By using U_sprint for benthic-associated fish and U_crit for pelagic fish, we may be able to compare a broader range of species' swimming abilities for use in a fish passage context.