Maneuverability of four species of coral-reef fish that differ in body and pectoral-fin morphology

Abstract

Maneuverability was measured during feeding and agonistic interactions in four sympatric species of coral-reef fish differing in body and pectoral-fin morphology: foureye butterflyfish, Chaetodon capistratus (deep body, low aspect ratio (AR) fins), beaugregory damselfish, Stegastes leucostictus (medium-depth body, low AR fins), ocean surgeonfish, Acanthurus bahanieusis (medium-depth body, high AR fins), and bluehead wrasse, Thalassoma bifasciatum (slender body, high AR fins). Damselfish turned faster, using median- and paired-fin propulsion, than either surgeonfish or wrasse, but their performance did not differ from that of butterflyfish during maneuvering behaviours common to all species. Each of these pairs had similar pectoral-fin morphology but exhibited an intermediate body morphology. This suggests that pectoral-fin morphology was more important in determining performance within maneuvers, and therefore butterflyfish and damselfish were superior maneuverers to surgeonfish or wrasse. To turn faster, fish shifted from median- and paired-fin propulsion to body and caudal-fin propulsion; however, turning radii were unaffected. Pectoral-fin morphology also determined the use of maneuvering behaviours within gaits that are used by fish to fractionate their locomotor-performance range. In general, morphological differences among species were correlated more often with behavioral differences than with locomotor performance. Fish differing in body and fin morphology express different gaits, and within these gaits, they express different behaviours; however, overall performance may converge.