Mote Marine Laboratory

Castro's Collection

By: Rebecca Evanhoe

José Castro stumbled into the world of shark identification in a freezer. As a young graduate student at a small southern college, he looked in the zoology lab fridge for food to feed some crabs — at that time, his subject of study. But a set of frozen shark jaws caught his eye instead. He asked his colleagues where the bull shark came from.

“Correcting” him, Castro’s colleagues told him the professor who found the jaws said they belonged to a lemon shark, not a bull. “But I knew it wasn’t. So I took a tooth home, keyed it out, and I was right,” says Castro, a senior scientist in Mote’s Center for Shark Research and a scientist with the National Oceanic and Atmospheric Administration.

Castro soon realized that such errors were common in the field because there simply weren’t any field guides to the sharks. “If we want to conserve sharks, we have to understand them. And understanding begins with a knowledge of the species,” he says.

Since no one had written the book on sharks, Castro decided that he would. It started with a small identification key for him and his colleagues to use around the lab. “I figured it’d take me a weekend,” he said, laughing. “So I made one, and that grew and grew.”

Five years later, in 1983, his simple key became the first edition of The Sharks of North American Waters, a 180-page field guide that detailed 112 shark species. Castro became so hooked on shark research that he switched from crab zoology to earning his Ph.D. in shark biology at Clemson University.

“It’s the only useful field guide book to the sharks of North America,” says Adam Summers, an assistant professor at the University of California, Irvine’s biomechanics lab who studies the physics of sharks’ cartilaginous skeletons. “Any time I’m in doubt about what sharks I’m going to find in a location or when I’m interested in the basic characteristics of the shark, I go to that book.”

Compiling all of the knowledge of an entire order of creatures is quite a feat. But Castro’s understanding of the shark runs far deeper than a simple listing of species; he knows the habitats, reproductive habits, biological features and behaviors of nearly all the known sharks.

His drive to study sharks is fueled by a desire to correct misconceptions. Castro’s dissertation laid down the facts about three unstudied species: the Atlantic sharpnose shark, the chain dogfish and the golden hammerhead shark. “I’m doing the same things I was doing when I was 5: Asking ‘What is it, why does it do this?’ Asking the same questions a child asks,” Castro says.

Castro’s expertise is also called upon by researchers from all over the world when a new or rare shark is found. In 1995, Castro was invited to Brazil to study a juvenile megamouth — only the ninth ever found. But to this day, Castro’s international fame comes from the fact that he wrote the first comprehensive shark guide now found on the shelves of shark researchers across the globe. The Sharks of North American Waters even made it to the big screen in the movie The Royal Tennenbaums when Margot Tennenbaum (played by Gwyneth Paltrow) is seen reading it in the film’s opening scene.

Now Castro is upstaging himself with a new “super-extended version” in the similarly titled The Sharks of North America. The book reflects 20 years of advances in shark research and covers 130 species.

The expanded edition is Castro’s labor of love; he has been working on additions in his free time and on weekends nearly since the first book was published. The new version is more of a reference book and includes detailed information on shark biology, geographic location, reproduction and migration habits.

To get the accurate photos and details, Castro collaborates with shark researchers worldwide to collect specimens. His book has required him to hunt down rare specimens from all over North America; he has gathered and borrowed sharks from Trinidad, Mexico, Portugal, Canada and Jamaica among others, including a rare small sleeper shark — the only one in the Western Hemisphere — found by a colleague in the middle of the Atlantic Ocean. Castro’s task is almost overwhelming for one person; he gets his sharks through his own personal contacts with fellow shark researchers and fishermen. “I beg for them,” he says. “And sometimes it’s just luck.”

What’s in a name?
The Sharks of North America will include the etymologies, or word origins, of all the shark species it describes — a feature almost unheard of in a scientific reference book.

José Castro has found that common names come from a variety of influences. Some sharks get their common names from their body shapes, such as the hammerhead’s distinctive profile. Others get their common names from the shark’s behavior. The tiny cookie cutter shark, for example, leaves a spherical bite in fish and large mammals like whales. The bite, called a crater wound, looks like it has been punched out with a round cookie cutter.

Other names, such as the common name “dogfish,” have more mysterious origins. Scientists often thought that the name dogfish implied that the shark’s meat was unfit for human consumption and suited only for the dogs. However, by researching a 13th century bestiary, or book on animal life, from the Bodleian library at Oxford University, Castro uncovered the dogfish’s true origins. The original Latin name was canes in mari — dogs in the sea — because they bite, as dogs do.

Learn more about: Shark Research