A tool for determining maximum sustained swimming ability of selected inland fish species in an Afrotropic ecozone

Abstract

Critical swimming speed ( Ucrit) predicts the maximum sustained swimming velocity that various fish species are able to sustain for prolonged periods. The objective of this study was to determine the U crit of Afrotropic ecozone fish, determine oxygen consumption at U crit and relate the resulting optimum flow requirements to effective movement through fishways under South African flow conditions. The selected fish species were Coptodon rendalli, Tilapia sparrmanii, Pseudocrenilabrus philander, Oreochromis mossambicus and Enteromius trimaculatus . Ucrit and oxygen consumption (MO 2) were measured in a swim respirometer at 5-min intervals, at increasing velocity increments of 0.5 cm·s −1 until volitional exhaustion. No significant differences were seen in the U crit values between C. rendalli, T. sparrmanii and P. philander , but all species significantly differed from O. mossambicus and E. trimaculatus, which had the highest U crit (17.6 ± 1.5 bl·s−1 and 18.2 ± 2.8 bl·s−1).

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