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Every year from June to December, hundreds to thousands of leopard sharks (Triakis semifasciata) congregate in this one particular spot along the southern California shoreline. Why are they here? Andrew Nosal answers this question and articulates why we should care. He carefully studied these sharks and their behavior over the course of several years. He discovered that most of the sharks are mature pregnant females. During the day, these pregnant females spend most of their time swimming in the warm, calm waters that are unique to the La Jolla area. At night, they forage for squid in a nearby marine canyon. Because sharks lack the ability to regulate their internal temperature (i.e., they are ectothermic), Nosal concludes the pregnant sharks are attracted to La Jolla’s warm waters to support the developing fetuses - much like hens sitting on eggs. He emphasizes the importance of protecting the leopard sharks, especially considering how they carry the next generation of sharks and could easily be wiped out by careless human activity.
Featured Research Articles
Nosal AP, Royer MA, Caillat A, Kisfaludy E, Wegner NC. (2014) Aggregation behavior and seasonal philopatry in male and female leopard shark (Triakis semifasciata) along the open coast of southern California, USA. Marine Ecology Progress Series. 499:157-175.
Nosal AP, Cartamil DC, Long JW, Luhrmann M, Wegner NC, Graham JB. (2013) Demography and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon along the open coast of southern California, USA. Environmental Biology of Fishes. 96:865-878.
Andrew P. Nosal is currently a postdoctoral researcher at Scripps Institution of Oceanography, where he conducts research on the behavior, ecology, and conservation of sharks and rays. Nosal is most interested in the causes and consequences of movement phenomena like aggregation (grouping) behavior, sexual segregation (spatial separation of males and females), and seasonal migration. He works closely with the Birch Aquarium and various media outlets to educate the public about sharks and rays and to dispel myths about these amazing animals. He is passionate about communicating science and, as a PhD student, received two awards for best student oral presentation at international conferences in Minneapolis, MN and Sapporo, Japan. When Nosal is not following sharks and rays, he loves hanging out and traveling with his wife and young daughter.
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