Effects of lateral morphology on swimming performance in two sturgeon species

Abstract

Fish express a high degree of diversity in morphology, which is closely related to behaviors such as swimming ability. The effect of morphology on swimming performance is explored using geometric morphometric analyses and classic critical swimming speed (Ucrit) tests in Chinese sturgeon Acipenser sinensis and Siberian sturgeon A. baerii. It was found that A. sinensis is a stronger swimmer compared to A. baerii, with an average 25% higher Ucrit (expressed in body lengths per second). In A. sinensis, the depth and length of the snout and the trailing edge length of the dorsal fin were negatively correlated with Ucrit, whereas the height of the trunk anterior, the leading edge length of the dorsal fin and anal fin, and the length and width of the ventral lobe were positively related to Ucrit; similar relationships between Ucrit and morphological characters of the anterior trunk, dorsal fin, anal fin and caudal fin were found in A. baerii. Moreover, although the degree of upward bending of the snout of A. baerii was negatively related to Ucrit, there was a positive relationship between the length of the caudal peduncle and Ucrit as well as between the dorsal tail lobe and Ucrit. In addition, the streamline index (SI) was calculated by comparing landmark coordinates on the trunk displayed in the relative warp, with its corresponding point on the NACA (the U.S. National Advisory Committee for Aeronautics) airfoil shape. SI showed that the body shape in RW1 of the A. baerii with more swimming capacity was more approximate to the NACA 0016 airfoil shape, but there was no such symmetry for A. sinensis, possibly due to body bending caused by stiffness.