Trophic Ecology of Pelagic Early-Juvenile Nassau Grouper, Epinephelus Striatus, During an Early Phase of Recruitment into Demersal Habitats

Pelagic early-juvenile Nassau grouper, Epinephelus striatus, (20.2–27.8 mm SL) were collected as they recruited from deep oceanic habitats into shallow bank habitats in the southern Exuma Cays, Bahamas, in 1991 and 1992, and their feeding ecology was examined. Evidence of filter feeding, particulate feeding, and piscivory was observed. A wide size range of prey items was ingested, including dinoflagellates as small as 80 μm in length and fish larvae as large as 9.4 mm SL. Numerically, non-thecate dinoflagellates dominated the diet, while volumetrically, fish larvae and mysids dominated the diet. Morphometry was utilized to elucidate the mechanics of ingesting the smallest and largest prey. Based on gill raker morphometry, the particle retention capabilities of E. striatus included dinoflagellates, but additional factors may have been operative. The ingestion of very large prey appeared to have been facilitated by protrusion of the upper jaw, which was seen to expand gape width by 87.5%. Both dietary and morphometric evidence suggest a high degree of trophic plasticity for E. striatus during this early, transitional phase of recruitment.