Swimming performance and behaviour of young-of-the-year shortnose sturgeon (Acipenser brevirostrum) under fixed and increased velocity swimming tests

Swimming performance and behaviour in fish has been shown to vary depending on the investigation method. In this study., an endurance swimming curve was generated for young-of-the-year shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818) (similar to 7 cm total length, similar to 2 g) and compared with values determined in a separate incremental swimming (critical swimming, U-crit) test. Using video, tail-beat frequency (TBF) was quantified and compared for fish swimming under both swimming tests. From the endurance-curve analysis, it was found that sturgeon did not display a statistically significant burst swimming phase. Maximum sustainable swimming speed (calculated to be 18.00 cm.s(-1)) from the endurance curve occurred at similar to 80% of U-crit (22.30 cm.s(-1)). TBF was similar at all speeds for both swimming tests, except at speeds approaching U-crit, where fish displayed TBFs of 4.29 Hz for the endurance protocol and 2.26 Hz for the U-crit protocol. TBF was more variable between individuals swimming at the same speed within the U-crit compared with the endurance protocol. Finally, a significant negative correlation was found between TBF and U-crit in individual fish, suggesting that station-holding may be an important energy saving strategy during swimming in this size class of sturgeon.