Kinematics and energetic benefits of schooling in the labriform fish, striped surfperch Embiotoca lateralis

Schooling can provide fish with a number of behavioural and ecological advantages, including increased food supply and reduced predator risk. Previous work suggests that fish swimming using body and caudal fin locomotion may also experience energetic advantages when trailing behind neighbours. However, little is known about the potential energetic advantages associated with schooling in fish that swim using their pectoral fins. Using the striped surfperch Embiotoca lateralis, a labriform fish that swims routinely with its pectoral fins, we found that pectoral fin beat frequencies were significantly higher for schooling individuals swimming in the front of a school relative to those swimming in the back, with trailing individuals benefiting from a 14.9 +/- 3.2% reduction in fin beat frequency (mean +/- SE). Trailing fish were estimated to benefit from a 25.6% reduction in oxygen consumption, based on correlations between swimming speeds and pectoral fin beat frequency and between swimming speeds and oxygen consumption of solitary fish. In addition, leading individuals in a school were estimated to have higher oxygen consumption than solitary individuals swimming at the same speed, based on their higher pectoral fin frequency. We suggest that this may be explained by differences in swimming behaviour, with schooling individuals continuously correcting their position relative to their neighbours whilst solitary individuals maintained a more rigid swimming pattern. Taking into account the increased oxygen consumption in leaders vs. solitary fish, we estimated that for an energetic advantage to occur in a school of striped surfperch as a whole, more than 78% of the individuals need to be in trailing positions, which is likely to be a common occurrence based on previous observations of other schooling species.