LOEWENSTEINER, D.A.*; TURINGAN, R.G.: Trophic ecomorphology of juvenile Cynoscion nebulosus (spotted seatrout): Intraspecific ontogenetic variability between Atlantic and Gulf populations of Florida.

Variation in prey capture ability may be one of the most important factors in determining survivability and cohort success in marine teleosts, especially during the larval and juvenile stages of ontogeny. During these stages substantial alterations to the prey capture mechanism occur at a rapid rate. It is hypothesized that these changes in morphology have consequences for the ability of a fish to select and capture prey. This study examines the feeding ecomorphology of juvenile C. nebulosus from newly settled recruits to late juveniles (≈10 mm to 100 mm SL) in populations along the Atlantic and Gulf coasts of Florida. Newly recruited juveniles feed primarily on copepods and mysid shrimp. Late-stage juveniles feed primarily on caridean shrimp, amphipods, and fishes. The onset of piscivory occurred at approximately 25 to 30 mm SL. Also, average prey size increased with fish growth. The morphological basis of these dietary shifts is analyzed. Specifically, data on variation in maximum gape height and width, mouth position, and lever mechanics will be presented. It is hypothesized that a shift in morphology from newly settled recruits to late juveniles is a consequence of feeding on larger, more elusive prey types. Concurrently, it is hypothesized that a possible shift in foraging location (benthos to mid-water) may correlate with variation in feeding mechanism. This study elucidates the link between feeding ecology and changes in the feeding mechanism during juvenile ontogeny.