Meeting Abstract

27.4  Monday, Jan. 4  Swimming performance, as indicated by U_crit and C-start escape responses, in surfperches (Embiotocidae) PERLMAN, B.M.; Moss Landing Marine Laboratories bperlman@mlml.calstate.edu

Surfperches are enigmatic labriform swimmers. Angle of insertion of the pectoral fin varies among species and theoretically allows for differing amounts of thrust to be generated, putatively affecting swimming performance. We predicted that speed and maneuverability trade-off in this clade of nearshore fishes. Specifically, we hypothesized that surfperches with lower fin angles would achieve a faster critical swimming speed (U_crit), but were less maneuverable, as indicated by bending during the C-start escape response. To address this hypothesis, we collected four surfperch species each with different pectoral fin angles (range: 35 to 51°). U_crit was measured in a flume. After acclimation, flow was set to 0.5 body lengths per second (BL/s) for 30 minutes, then increased by 0.25 BL/s every five minutes until U_crit was reached, as indicated by the onset of burst-and-glide behavior. We recorded maximum fin beat frequency and U_crit. In separate experiments, we elicited C-starts from individual fish, recording the escape response with a high-speed digital camera at 250 fps. We measured maximum angle of body curvature during Stage 1, duration of Stage 1, duration of C-start escape response, escape trajectory angle (ETA), and peak angular velocity. ANOVA revealed differences among species in that surfperches with lower fin angles achieved a faster U_crit and a higher maximum fin beat frequency. For the five C-start variables, we conducted a PCA to reduce the dimensionality of the dataset. PC1 described duration and angle of Stage 1 and ETA. PC2 described C-start duration and peak angular velocity. ANOVA performed on these PCs revealed that species with lower fin angles turned faster and had greater body bending. Contrary to our prediction, species with lower fin angles reached both faster U_crit and greater body bending than species with higher fin angles.