TURINGAN, R.G.: Functional and morphological bases of prey-capture performance in marine-fish larvae.

A critical period, marked by a rapid decline in population size, occurs immediately following yolk-absorption during the larval phase of marine teleosts. Biotic and abiotic factors associated with mortality during this critical period have been identified, but the causal link between these factors and mortality is not clearly understood. This study explores the link between development of the feeding mechanism and prey-capture performance in larval red drum (Sciaenops ocellatus). Lower-jaw depression in red drum larvae developed from a simple mechanism around first-feeding, driven by the hyoid-mandible linkage (i.e., the hyoid stage), to a more complex mechanism around metamorphosis, driven by the hyoid- and opercular series-mandible linkages (i.e., the hyoid-opercular stage). This two-stage development of the feeding mechanism was associated with differences in feeding performance: (1) less than 50% of larvae fed during the hyoid stage whereas almost all larvae at the hyoid-opercular stage consumed prey; and (2) first-feeding larvae preferred small and less elusive prey relative to conspecifics at metamorphosis, which preferred larger and more elusive prey. Our ability to understand the functional relationship between development of the feeding mechanism and prey-capture performance enhances our ability to understand the underlying causes of mortality in larval fishes.