Discovery of a Great Hammerhead Nursery

Happy Shark Week (if you celebrate), and I’m so excited to share our newly published open access paper about our research on juvenile great hammerheads (Sphyrna mokarran) with you! (It’s been hard to keep this one to ourselves).

Great hammerheads are an iconic shark species which have undergone significant population declines globally. In 2019, they were assessed as Critically Endangered by the IUCN Red List, which reported overfishing as the greatest threat to their survival. Great hammerheads are known to make incredible long-range migrations and cross state and international boundaries, making them challenging to protect as adults. Little is known about where they are born or where they spend their early years of their life, although there have been scattered reports of juveniles from the Gulf of Mexico, the Florida Keys, and one report from Georgia.

Identifying habitats that are important to juvenile sharks matters because young sharks are often the most vulnerable individuals in a population, and their survival is vital to the future of their species. Many juvenile sharks spend time in “nursery areas”—places where they are less likely to be eaten by predators, or where food resources are abundant. They then expand their ranges as they age, covering more distance as they grow larger. Identifying nurseries has long been a conservation priority for managers and scientists. After several years of research, our team has collected the first scientific evidence of a nursery area for great hammerhead sharks on the Atlantic coast of the United States—within sight of the skyline of Miami, Florida.

There’s a three-part established test for an area to be identified as a shark nursery: 1) Juvenile sharks are more commonly encountered in that habitat than elsewhere; 2) they remain in the area for extended periods; and 3) The area is used repeatedly over years. Our results demonstrate that this area definitely meets two of these criteria, with preliminary evidence that it also meets the third. We’ve found the same habitat may be a nursery area for several other shark species too, including scalloped hammerheads, another Critically Endangered species!

Although great and scalloped hammerheads are protected in Florida waters and must be released if caught, hammerhead sharks often die or suffer serious harm from capture stress. Some of these juvenile individuals were caught with hooks from prior encounters with recreational anglers still embedded in their jaws. We hope learning more about this nursery can help us reduce threats to and better protect these small sharks. We can’t wait to share further updates as new results come in from the project’s telemetry expansion, supported by the Nature Trust of the Americas and a National Geographic Explorer Grant.

Our short scientific paper documenting this work is available open access through the journal Conservation Science and Practice, you can visit the project website here, or I hope you will watch the incredible video (also embedded at the top of the post).

Shark Science Monday: the Known Unknowns of Shark Conservation

“There are known knowns; there are things we know we know. We also know there are known unknowns, that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know.” – Former U.S. Secretary of Defense Donald Rumsfeld.

As nature documentary viewers often hear, there is a lot about sharks and rays that scientists don’t know… but what are the most important things that we need to know? A new paper written by Colin Simpfendorfer, Will White, and former Shark Science Monday interview subjects Michelle Heupel and Nick Dulvy attempts to identify these “known unknowns” of shark and ray conservation. “The importance of research and public opinion to conservation management of sharks and rays: a synthesis”, which arose out of the 2010 Sharks International conference, is the most complete record ever created of the research questions that we need to answer in order to better conserve and manage these animals. For young shark researchers eager to work on projects with practical conservation importance, this paper is a great place to start looking for ideas. Additionally, future published work that claims to be important for conservation and management would do well to cite it, and anyone interested in this subject should read it.

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Shark Science Monday: WhySharksMatter discusses social media and shark conservation

For this week’s edition of Shark Science Monday, check out this video of a presentation I gave at the 2nd International Marine Conservation Congress last May. My talk focused on how social media technology can benefit (and has already benefited) the shark conservation movement. It was part of a symposium organized by the IUCN Shark Specialist Group.

I’m happy to answer any questions about it.

Shark Science Monday: The Sharks and Shark Fisheries of India

Divya Karnad is a wildlife biologist in India focusing on marine issues. She began her career working with olive ridley sea turtles, studying hatchling responses to beach lighting and temperature-dependent sex determination. Lately, she has been focusing on marine fisheries issues on both coasts of India, including shark fishing and the fin trade. She met WhySharksMatter at the International Marine Conservation Congress, and agreed to write a guest post for Southern Fried Science.


A soupy end to Indian Sharks

Thomas and Arulsingh, fishermen who hail from Kanyakumari, hauled up their nets and fishing lines on a beach in southern India. The catch was special and I was privileged, as an outsider, to be invited to watch as this enormous fish was sliced, its fin, the most valuable part, handled with extreme care. The shark fin, I was told, would fetch a lot of money, despite the fact that it was not a hammerhead, which fetches the best price. Nevertheless, the fishermen revealed, there were several more where this one came from, and they could be caught easily using specialized hooks and lines. Altogether estimated to host about 70 species of shark, 18, including two species of hammerheads, spadenose, requiem and milk sharks, are often landed for fins or meat from Indian waters. Different parts of the Indian coast have different species compositions of sharks, with the northwest reporting large proportions of spadenose sharks, hammerheads along the south west coast, and requiem, hammerheads and milk sharks along the east coast. Sharks are usually brought to shore before finning and the flesh is consumed locally while the fins are exported to South-east Asian markets.

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Shark Science Monday: How you can help WhySharksMatter tag sharks!

EDITOR’S NOTE: THIS OPPORTUNITY IS FROM 2011, AND IS NO LONGER VALID 

Those of you who follow me on twitter know that in addition to being a grad student, I work with the South Carolina Department of Natural Resources coastal shark survey. This summer, we will be catching and tagging sharks, and we need your help!  From mid-May through August, we’ll take the boat out 2-4 times a week for single-day surveys. We leave around 6 or 7 in the morning and return mid to late afternoon. There is often room for a volunteer or two, and the help is always appreciated.

Since I started advertising this opportunity last week, I’ve received over 150 e-mails inquiring about it. Many of you are asking the same questions, and while I”m always happy to answer questions about sharks, I’m instead going to answer the most common questions in this post.

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