Tooth Morphology and Diet over Ontogeny in Western Atlantic Sandbar Sharks

• Maxwell Weaver, Marine Science, University of Delaware

• Aaron Carlisle, Marine Science and Policy, University of Delaware

The sandbar shark (Carcharhinus plumbeus, Nardo 1827) is a large requiem shark ubiquitous to the Delaware Bay. Extensive research has been conducted by UD’s TRASER laboratory on their trophic ecology and resource use within the Delaware Bay. As neonates ( <62.4 cm), sandbar sharks consume crustaceans, then as small juveniles ( <99 cm) their diet shifts to include benthic fishes. During their large juvenile stage (<157-167cm), they then begin to prey on small nektonic fishes. Once fully grown (>157-167cm), adults will predominantly hunt other elasmobranchs. This shift in their diet is expected to coincide with a presumed change in the morphology of their teeth as proposed by Garrick et al. 1982. 

Using novel tooth measurements from Goodman et al. 2022, and methods adapted from Cullen & Marshall 2019, we found that there is a marked morphological shift in the teeth of neonate sharks to adult sharks corresponding to both their maturation and known ontogenetic dietary shifts. Teeth at the same position within the mouth may not only grow larger but become proportionally thinner or broader as the animal ages and its chosen prey changes. Measurements were taken from both live and dead individuals from only the Western Atlantic population of sandbar sharks, focusing mainly on the Delaware Bay. Shed teeth from two captive neonate specimens at the TRASER lab, as well as shed teeth from the pair of sharks in the Baltimore National Aquarium were used as supplementary data but remain limited as estimates. 

As shark populations rebound in the Western Atlantic and the need for more nuanced insight into the life history of these animals arises, this research will help provide a more complete understanding of the sandbar shark’s role in our oceans.