Effect of Pectoral Fin Ray Removal on Station-Holding Ability of Shovelnose Sturgeon

The effect of fin ray removal on swimming performance was evaluated for shovelnose sturgeon Scaphirhynchus platorynchus from the lower Mississippi River. Immediately upon collection, the marginal pectoral fin ray was removed from some fish, and others were left unclipped as a control group. Fish were promptly returned to the laboratory and held in 1,300-L recirculating tanks at 21-26°C. After a minimum recovery time of 48 h, individual fish were placed in a 1,000-L, Brett-type swim tunnel, and their ability to maintain station in flowing water by swimming, skimming, or substrate appression was tested by subjecting fish to increasing speeds beginning at 10 cm/s. After a 60-min swimming bout, speed was increased by 10 cm/s. This was repeated until the fish could no longer maintain station. Fin ray removal had no significant effect on critical station-holding speed (CSHS). The CSHS (mean ± SE) of fin-ray clipped fish was 60.1 ± 4.2 cm/s, and that of unclipped fish was 59.2 ± 3.0 cm/s. Correlation analysis and analysis of variance indicated that collection method, water temperature, size of fish, and time spent in the laboratory had no significant effects on CSHS. Tail beat frequency increased with water velocity, but clipped and unclipped fish were not significantly different. Results indicate that removal of the pectoral fin ray has little or no effect on station-holding ability in shovelnose sturgeon