Master of Science (M.Sc.)
Virginia Institute of Marine Science
The sandbar shark, Carcharhinus plumbeus, is the most abundant large coastal shark in the temperate and tropical waters of the northwest Atlantic Ocean. The Chesapeake Bay, Virginia and adjacent waters serve as a nursery ground for C. plumbeus as well as many other fauna. Characterizing the diet of a higher trophic level predator such as the sandbar shark sheds light on a small portion of the temporally and spatially complex food web in the Bay. This study describes the diet of the sandbar shark, highlighting differences in diet within various portions of the nursery area, as well as ontogenetic changes in diet.
Stomach samples were obtained in 2001 and 2002 from 232 sharks caught in gillnets or by longline gear. Historical data from the Virginia Institute of Marine Science (VIMS) Shark Ecology program were also analyzed. Ontogenetic changes in diet were evident, with crustacean prey decreasing in importance and frequency with increasing shark size, and elasmobranch prey importance and frequency increasing with increasing shark size. While previous research in Chincoteague Bay, VA showed the blue crab, Callinectes sapidus, as the dominant crustacean in sandbar shark diet, the mantis shrimp, Squilla empusa, dominated the crustacean portion of the diet in this study.
Differences in diet were mainly attributable to location of shark capture. Small juveniles (< 80 cm precaudal length) in the lower Chesapeake Bay ate significantly more fishes, whereas Eastern Shore juveniles ate more crustaceans. The type of crustacean consumed varied within areas of the Eastern Shore, with more portunid crabs consumed in waters near Wachapreague and more mantis shrimp consumed near Sand Shoal Inlet. This study was not able to detect any change in diet over time due to insufficient sample sizes and the effect of location.
© The Author
Ellis, Julia K., "Diet of the Sandbar Shark, Carcharhinus plumbeus, in Chesapeake Bay and Adjacent Waters" (2003). Dissertations, Theses, and Masters Projects. Paper 1539617797.