Relationship Between Lateral Morphology And Swimming Performance Of Two Sturgeon Species

Maximum aerobic swimming performance of fish is significantly important fortheir survival. Swimming performance of sturgeon has not been measured extensivelyfor sturgeon. Critical swimming speed of twelve2-ages Chinese sturgeons Acipensersinensis and eleven Siberian sturgeons A. baerii were determined by modifiedBrett-type swimming flume. Ucritwas regressed by body size. It was suggested that theabsolute value of Ucrit(U’crit=105.97±2.19cm s^-1, mean±S. E.) and its relative valueto body length (Ucrit=1.72±0.05BL s^-1) of Siberian sturgeon were both significantlyhigher than Chinese sturgeon (U’crit=79.45±1.83cm s^-1, Ucrit=1.38±0.03BL s^-1)（P<0.001）. There was a negative correlation between body size and Ucritin Siberiansturgeon （P <0.05）, while no correlation in Chinese sturgeon （P>0.05）. Comparison ofChinese and Siberian sturgeon’s Ucritprovided important data for analyzing behavior ofsturgeon. Ucritof large-body-sized （>40cm） sturgeon was rarely documented, so thisstudy filled such knowledge gap. In addition, Chinese sturgeon was an endangeredspecies in China. This study which determined Ucritof Chinese sturgeon firstly providedkey evidence for selection of place of releasing and designs of fish way.Morphometrics was important for study on systematic, ecology and evolution offish. Sturgeon has unique morphology. Local morphology of sturgeon had beenanalyzed by multivariate analysis, but rarely by Geometric morphometrics. Elevenlateral morphological characteristic measurements were selected for multivariateanalysis. Twenty six landmarks were set for relative warp analysis. Morphologicaldifference of twelve juveniles of Chinese sturgeon and Siberian sturgeon was compared.It was suggested that Chinese sturgeon’s snout depth and length, head depth and length,depth of posterior trunk and length of leading edge of dorsal fin were significantly morethan Siberian sturgeon, while its length of caudal peduncle and tail lobes weresignificantly less （P <0.001）. It was suggested that the power of Geometricmorphometrics was stronger than traditional multivariate analysis. Four landmarks werefirstly used to fit a cubic curve to correct the unnatural bend caused by slender soft body so that relative warp analysis could be successfully applied in sturgeon. It provided anew sight and more effective tool for morphological and related study in sturgeon.Mechanical information was important for functional morphology of fish, becauseit was dangerous to conclude function of morphology without aid of mechanicalanalysis. The locomotor function of fish had been documented, but there were fewstudies on effect of morphological variation on swimming performance. Intraspeciesmorphological variations of juveniles of Chinese and Siberian sturgeon were analyzedby relative warp analysis. Ucritwas multiple regressed by intraspecies morphologicalvariations and body size. It was suggested that Chinese sturgeon’s snout length anddepth, depth of trailing edge of dorsal fin and dorsal-ventral forward bending of bodywere negatively correlative with Ucrit, while depth of anterior body, length of anal finand ventral lobe of tail fin, vertical degree of trailing edge of tail fin and distance fromtail fork to caudal peduncle were positively correlative with Ucrit（P <0.01）. Siberiansturgeon’s depth of anterior body, anal fin length, caudal peduncle length and length oftail lobes were positively correlative with Ucrit, while its length of trailing edge of dorsalfin and angle of bending upward in snout were negatively correlative with Ucrit（P <0.001）. Such morphological variations included simple biofluid mechanical theory. Theeffect of morphological variations onto swimming performance was interpreted bystudies of morphological locomotor function. The linear morphology-swimmingrelationships of two species were compared. Fish fin was firstly brought into analysis inthis study. It provided important data and a new sight for understanding pattern ofmorphological locomotor function in sturgeon.In addition, streamlined body could reduce pressure drag effectively under highReynolds number. However, there were few studies on streamlined body of fish.Streamlined index （SI）, was calculated by comparing landmark coordinates on the trunkdisplayed in the relative warp, and its corresponding point on the NACA （the U.S.National Advisory Committee for Aeronautics） airfoil shape. SI showed that the bodyshape in RW1of the A. baerii with more swimming capacity was more approximate toNACA0016and0017airfoil shape, but there wasn’t any such symmetry for A. sinensismight due to the body bending caused by stiffness.