Using eDNA to Track the Spatiotemporal Dynamics of Large Shark Populations

Shark populations have faced significant declines due to overfishing but are recovering through conservation efforts, necessitating accurate monitoring tools. This study aimed to evaluate environmental DNA (eDNA) as a non-invasive complementary method to Mote Marine Laboratory's traditional fishing Large Shark Survey (LSS) along Florida's western coast, comparing efficiency for assessing abundance and diversity. In December of 2025 and February of 2026, 500 mL water samples were collected at two depths across five sites offshore of Midnight Pass and Siesta Key using a niskin bottle, totaling 40 samples over the course of 2 months. Samples were filtered using DNeasy kits, preserved, and sequenced via metabarcoding using a mitochondrial, COI locus and compared to an elasmobranch specific database. Based on Mote’s known shark presence data, we expected 8 large shark species detected, including sandbar sharks and great hammerheads. We were able to detect these species, notably sandbar sharks and great hammerheads. We also found evidence of seasonal shifts in elasmobranch diversity, despite the short term nature of this project. This validates environmental DNA as a reliable, efficient alternative that enhances traditional surveys by capturing non-feeding or rare sharks, fostering long-term Eckerd-Mote collaboration, and informs conservation policies for regional shark dynamics.

For more information:  lsanchez1@eckerd.edu

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