Date of Award


First Advisor

Thomas Coote

Second Advisor

Sarah Snyder


The burgeoning and grossly unregulated global shark fishery is overfished to unsustainable levels. Elasmobranchs, a group of cartilaginous fish including sharks and rays, are particularly vulnerable to overfishing due to late maturation and low fecundity. Southern New England, specifically Massachusetts, Connecticut, and Rhode Island, has a historic reliance on fisheries and seafood consumption. The appetite for seafood in Southern New England includes top-predators such as the Shortfin Mako shark (Isurus oxyrinchus), Common Thresher shark (Alopias vulpinus), and Swordfish (Xiphias gladius). The visual similarity of Mako and Swordfish fillets is remarkable, and as such, this study aimed to evaluate the percentage of substitutions in shark and Swordfish meat collected from markets and grocery stores in Southern New England. A DNA-barcoding methodology was applied to a fragment of the mitochondrial cytochrome oxidase I (COI) subunit to determine species-level identification of 40 collected tissue samples. According to genetic analyses, Swordfish accounted for 64.1% of the samples collected, and Mako comprised 28.2% of the total, indicating that these two species are most readily available and heavily consumed in New England, while Thresher represented only 7.2%. Phylogenetic analysis revealed four substitutions. One substitution, labeled ‘Mako’ in the market, was identified as Thresher. Three further substitutions, labeled as ‘Swordfish’ in the market, were identified as two samples of Mako, and one of Thresher. The composite substitution rate is 10.2% for Southern New England markets. Mako and Thresher, both listed on the CITES Appendix II List, comprised 35.4% of samples collected. With global population declines in shark stocks, assessments of CITES Appendix II and highly consumed species are critical for conservation efforts. Additionally, the mislabeling of shark and Swordfish meat poses a consumer rights issue alongside the challenge of managing healthy stocks of Mako, an IUCN Red List Endangered species, and Thresher, an IUCN Red List Vulnerable species.

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