Bite, swab, identify: Validating molecular tools for detecting depredating shark species

Area of Science:

• Marine Biology
• Fisheries Science
• Conservation Genetics

Background:

• Depredation by sharks is a growing concern in recreational fisheries, impacting management and public perception.
• Identifying depredating species is crucial, but DNA swabbing techniques face uncertainty due to potential environmental DNA (eDNA) contamination.

Purpose of the Study:

• To evaluate the accuracy of DNA swabbing for identifying shark species involved in depredation events.
• To compare genetic identification from swab samples with video-confirmed depredation.

Main Methods:

• Collected DNA swab samples from depredated fish following four recorded events in Jupiter, Florida.
• Analyzed genetic material from swabs to identify the predator species.
• Compared genetic results with video evidence of the depredation events.

Main Results:

• DNA analysis correctly identified the responsible shark species in three out of four cases.
• Bull shark, lemon shark, and great hammerhead shark were accurately identified.
• No amplification was achieved for the great barracuda depredation event, indicating specificity.

Conclusions:

• Swab-based molecular techniques are validated as accurate tools for identifying depredating shark species.
• The study confirms the absence of misleading environmental DNA (eDNA) signals in swab samples.
• This non-invasive approach offers a valuable method for studying predator-prey dynamics and informing fisheries management.