The influence of oral anatomy on prey selection during the ontogeny of two percoid fishes,Lagodon rhomboides and Centropomus undecimalis

Synopsis Ontogenetic increases in mouth size and changes in dentition of percoid fishes may affect the size and species of prey selected, thus influencing the fundamental trophic niche. To examine the influence of oral anatomy on prey selectivity by pinfish, Lagodon rhomboides, and snook, Centropomus undecimalis, two co-occurring percoid fishes with contrasting mouth morphologies, the mouth size, dentition, stomach contents, and available prey during ontogeny were quantified. Based on the presence of prey fragments in stomach contents and direct behavioral observation, prey were categorized by the feeding mode used during capture (suction/ramfeeding or biting). Centropomus has a larger size-specific gape than Lagodon during all ontogenetic stages. Although both feeding modes were used by Lagodon during ontogeny, the amount of prey captured using suction/ram-feeding declined and the amount of prey captured by biting increased with standard length. This change in feeding mode was associated with a change in incisor shape and width: Lagodon < 39 mm SL possessed narrow, pointed incisors and strongly selected amphipods, which are captured using suction/ram-feeding; Lagodon> 40 mm SL possessed wide, flat-topped incisors and significantly increased their selectivity for polychaetes, which are captured by biting. Centropomus used ram-feeding to capture prey at all ontogenetic stages. Size-selective feeding by Centropomus was apparent but could not be due to gape-limitation alone, because average prey body depth was only 45% of gape and was not proportional to absolute mouth size increase during ontogeny. Dietary diversity was greatest during the transition from suction/ram-feeding to biting in Lagodon. Lagodon had a higher dietary diversity at all ontogenetic stages than Centropomus, due in part to Lagodon's use of multiple feeding modes.