DNA metabarcoding of cloacal swabs provides insight into diets of highly migratory sharks in the Mid-Atlantic Bight.

The abundances of migratory sharks observed throughout the Mid-Atlantic Bight (MAB) during productive summer months suggests that this region provides critical habitat and prey resources to this taxon. However, the principal prey assemblages sustaining migratory shark biomass in this region is poorly defined. We applied high-throughput DNA metabarcoding to shark feces derived from cloacal swabs across nine species of Carcharhinid and Lamnid sharks to (1) quantify the contribution of broad taxa (e.g., invertebrates, fishes) supporting shark biomass during seasonal residency in the MAB and (2) determine whether species displayed distinct dietary preference indicative of resource partitioning. DNA metabarcoding resulted in high taxonomic (species-level) resolution of shark diets with Actinopterygian and Elasmobranch fishes as the dominant prey categories across the species. DNA metabarcoding identified several key prey groups consistent across shark taxa that are likely integral for sustaining their biomass in this region, including Atlantic menhaden (Brevoortia tyrannus), Atlantic mackerel (Scomber scombrus) and benthic elasmobranchs including skates. Our results are consistent with previously published stomach content data for the shark species of similar size range in the NW Atlantic Ocean, supporting the efficacy of cloacal swab DNA metabarcoding as a minimally-invasive diet reconstruction technique. The high reliance of several shark species on Atlantic menhaden could imply wasp-waist food-web conditions during the productive summer months, whereby high abundances of forage fishes sustain a diverse suite of migratory sharks within a complex, seasonal food web. This article is protected by copyright. All rights reserved.