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Shark tagging success

Thirty-four sharks were tagged along Florida’s Gulf Coast for studies designed to benefit their populations during a successful research cruise conducted April 17-21 by five scientists, two graduate and 40 undergraduate students from New College of Florida, Eckerd College, Mote Marine Laboratory and The Nature Conservancy (TNC).

The team attached identification tags to 21 blacktip sharks, including 10 females revealed to be pregnant by ultrasound; six bull sharks; three blacknose sharks; and four tiger sharks. Of those, one blacktip and five bull sharks received acoustic tags that will ping when the sharks pass underwater receivers in bay passes, and one bull shark and one tiger shark were tagged by TNC scientists with satellite transmitters to track their migratory movements in the Gulf.

The cruise, conducted on the Florida Institute of Oceanography ship R/V Bellows, was designed to enhance knowledge about the shark species using southwest Florida’s coastal habitats. Data from acoustic and satellite tags, and recaptures of conventional (plastic) ID-tagged sharks, are important for understanding shark populations in the Gulf of Mexico overall, and they can be compared with past data to investigate possible changes over time. Multiple shark species are valuable to Gulf fisheries and to ecosystems where they serve as top predators in the food web, maintaining a healthy community.

“It’s amazing how many studies we supported in a five-day trip, while also giving two groups of college students an exciting, hands-on learning experience,” said Dr. Jayne Gardiner,  Assistant Professor of Biology at New College of Florida. “The group fitted sharks with advanced tags and collected data and samples to serve multiple projects at our institutions and elsewhere. Blood samples and ultrasound results will support studies of shark pregnancy by our colleagues at University of North Florida, and clips of fin tissue will support assessments of genetic diversity. Our catch, release and tagging efforts provided data for studies of habitat use. One of my interests is why sharks locate and use certain habitats, such as nurseries where young sharks start their lives.”

Participant Dr. Robert Hueter, Senior Scientist at MoteMarine Laboratory, said: “The relatively high catches last week are a good indicator of the resurgence of depleted shark populations following 25 years of fisheries management designed to achieve sustainability of these populations. Also, the conventional and electronic tagging will add to our knowledge of where these animals go, when, and what critical habitats they need to survive.”

Blacktips sharks, the most abundant catch, are fished commercially and recreationally but their populations are faring better than those of many other large, coastal sharks. Gardiner notes that studying the life history of this successful species may provide clues for understanding and conserving other species that aren’t faring as well.

Dr. Jorge Brenner, a Marine Scientist with TNC studying the blueways (migratory corridors) of megafauna in the Gulf, was responsible for satellite tagging two sharks during the cruise.

“Assessing the migratory pathways of these juvenile sharks will allow us to understand what habitats are essential for their development in the Gulf of Mexico and identify opportunities for their conservation,” Brenner said. “Additionally, we hope this research will support a current Mote study on the interaction between bull sharks and one prey animal, juvenile bottlenose dolphins, since bull sharks were fitted with acoustic tags to assess their fine-scale movements in Sarasota Bay.”

This work highlights the collaboration between Moteand TNC in assessing the status and pathways of migratory sharks. The two institutions recently signed an agreement for collaboration in research and conservation in the wider Caribbean region.

 

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