Meeting Abstract

137.3  Monday, Jan. 7  Detection and characterization of an ontogenetic diet shift in the Naked Goby, Gobiosoma bosc D’AGUILLO, M.C.*; HAROLD, A.S.; College of Charleston ; College of Charleston mcdagu@email.wm.edu

Ontogenetic shifts in diet allow organisms to maximize energy conservation, presumably by reducing the time spent foraging or increasing net energy intake. As many diet studies are descriptive and report only frequency or counts of prey items, the ability to precisely quantify and describe a diet shift can be challenging. The goals of this study were to report the diet composition of the Naked Goby, Gobiosoma bosc, and examine if there is a threshold body size at which the diet shifts from dominance of meiofauna to dominance of macrofauna. Gobiosoma bosc specimens were collected from oyster reefs in the Charleston Harbor estuary by examination of removable oyster shell and seine. To investigate diet composition, the digestive tract was removed from G. bosc individuals and prey types were identified to the lowest taxonomic level possible, measured, and enumerated. Stomach content analysis reveals G. bosc primarily consumes harpacticoid copepods from the meiofauna, and polychaetes and amphipods from the macrofauna. The consumption of macrofauna begins at a small predator size (11 mm standard length), and while the number of macrofaunal organisms ingested does not increase with predator size, the volume of macrofauna does. Both the number and volume of meiofaunal organisms consumed decreases with predator standard length, suggesting strong reduction of meiofauna in the diet around a predator size of 25 mm. The use of different prey response variables to characterize a diet shift, with insights into the potential roles of morphology and behavior driving this particular diet shift, will be discussed.