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Dr. John McCosker
  • A Living Fossil

    0:56, Footage: Al Giddings
  • Evolution

    1:16, Footage: Al Giddings
  • Sharks

    1:39, Footage: Al Giddings
  • Galapagos in a Submersible

    1:26, Footage: Al Giddings
  • John McCosker Slideshow

    11 Photos
    Dangerous Reef, Australia.  Photo: Al Giddings Ichthyology Research Collection.  Photo: Dong Lin John McCosker, portrait.  Photo:Dong Lin Snorkeling in a California kelp bed.  Photo:Al Giddings Treating an injured white shark.  Photo:Susan Middleton JSL submersible launching, Cuba.  Photo:John McCosker Examining specimens, Mexico.  Photo:Al Giddings Underwater at Galapagos.  Photo:Al Giddings Feeding a white shark, Australia.  Photo:Al Giddings Lecturing on white shark behavior.  Photo:Pam McCosker Twilight Dive, Grand Comoro Island.  Photo:Al Giddings

When he is not deep-sea diving or researching white shark behavior, Dr. John McCosker's interests include aquatic animal evolution and behavior, plus discovering and cataloguing the fishes of the Galapagos Islands.

Coelacanth Fossil


In 1938, when a fisherman off the coast of Africa inadvertently caught a coelacanth, it was heralded as the biological find of the century. Thought to be the missing link between amphibians and fish, coelacanths are big, oily, strange-looking fish that grow up to six feet in length and weigh 200 pounds. According to the fossil record, the coelacanth was thought to have gone extinct 80 million years ago. John McCosker, Chair of Aquatic Biology, says, “It was like finding a living T. rex.”

In 1975, the California Academy of Sciences sent McCosker and a team of oceanographers to Grand Comore, an island in the Indian Ocean off the eastern coast of Africa. McCosker's mission: To learn as much as possible about the coelacanth. Despite accidentally wandering into the midst of an insurrection against French colonialists, McCosker still managed to obtain two frozen coelacanths, an event preserved on a 50-franc stamp issued by the Comoro Islands.

Packing his specimens in dry ice, McCosker made his way back to the states, where he sold one specimen to his alma mater—the Scripps Institution of Oceanography, based in La Jolla, CA. That sale helped to pay for the expedition, enabling McCosker to dissect the remaining coelacant. Both specimens provided researchers at numerous laboratories with an unparalleled opportunity to perform dissections, examine tissue, and determine if coelacanths were, in fact, the missing relative that linked fish and amphibians.

Unfortunately for the coelacanth, that special designation was not to be. “It was once thought that the coelacanth walked out of the water on its bony limb-like fins and became an amphibian,” says McCosker. “That designation now goes to the lungfish.” Today, the coelacanth is regarded as a still-living remnant of an ancient evolutionary line. However, McCosker notes with satisfaction, the coelacanth survives in the popular imagination as a form of insult in politics, where it is a term used to describe politicians too old, fossilized, and set in their ways to change.

Great Whites

When John McCosker, Chair of the Department of Aquatic Biology, started his research on great white sharks, not much was known about them except what was blared across newspaper headlines whenever a human was attacked. McCosker, who grew up surfing and scuba diving in Southern California, began to ask some simple questions: Are great whites really dangerous? What are the risks to swimmers? And why were attacks on surfers suddenly on the rise?

In 1980, McCosker got a phone call from Al Giddings, an underwater filmmaker famed for his bravery and ability to capture rare underwater images. Giddings had been part of the 1975 expedition to the Comoro Islands that produced a coelacanth and the first-ever photographs of many unknown creatures.

Now he had a simple question for McCosker. “What's the most exciting thing a marine biologist can do on camera?”

To McCosker the answer was obvious. “Get in the water with great white sharks.”

McCosker was the first trained marine biologist to swim with the sharks. McCosker and Giddings began their hunt for great whites off the coast of South Australia. Together in an underwater cage, they began the studies that would transform the great white from a fearsome man-eater shrouded in misunderstanding to the dominant, albeit respected, species at the top of the ocean food chain.

Using fairly primitive materials, like barbed brass spear points, rudimentary radio transmitters and long sticks with a sharp point, the two men tagged sharks and inserted transmitters inside their musculature. They examined the sharks' body temperature and discovered them to be warm-bodied creatures.

Along the way, McCosker came up with a theory about why humans (especially surfers) were attacked by great whites with increasing frequency. As surfing grew in popularity and matured as a sport, surfers sought ways to go faster. They adopted shorter boards with spit tails for maneuverability. From a shark's point of view, the new surfboard design resembled a seal-sized lunch.

In his decades-long career, McCosker has interviewed dozens of people attacked by sharks. Now he sees the tables turned. Sharks are under unprecedented attack by man. Tens of millions of sharks are being killed each year for the Asian sharkfin soup market. Their fins are hacked off and the sharks are dumped back into the ocean to die.

“It's tragic for sharks, and tragic for the ecosystem,” McCosker says. “Sharks are top-level predators for the ocean ecosystem. And the oceans are collapsing. When the sharks go, there are no controls,” says McCosker. “If there are no sharks, there are no safety checks.”

These safety checks protect the survival of the entire ecosystem. Once a top line predator disappears, the next species down the food chain expands in abundance and eats most everything that's below it in the food chain, and then their population crashes. The cascading effect can be seen today. As great whites disappear, sea lions have helped to decimate the salmon population.

“Eventually,” McCosker predicts, “we'll have nothing left in the oceans until we get to jellyfish.” If the sharks disappear, seals will soon have nothing to eat. As counterintuitive as it seems, that's why even seals need white sharks.

The Galapagos Islands

For environmental biologists, the Galapagos Islands remain deeply inspirational. Most of the same species of finches and giant tortoise that Charles Darwin observed in 1835 as he wrote The Origin of the Species are still there, undisturbed by man. Nearly 75% of all land birds and more than 90% of the terrestrial mammals and reptiles are unique to the Galapagos. Close to 96% of the endemic species living on the Galapagos at the time of Darwin are still intact.

The Galapagos present an amazing opportunity for scientists to add to the knowledge base of biodiversity. Island ecosystems are easier to study than continental landmasses. These islands are a living laboratory of evolution. They are literally swarming with species that live nowhere else.

To a marine biologist like John McCosker, the Galapagos represent a challenge to study evolutionary biology in a place where Darwin never dreamed of going—under the ocean. This is a world Darwin never saw.

McCosker, currently the Chair of Aquatic Biology, has been to the Galapagos on several expeditions. With his filmmaking colleague Al Giddings, McCosker has ventured out in a deepwater submersible capable of withstanding the enormous pressure at 3,000 feet on the bottom of the ocean floor. He's discovered previously unknown sharks, eels, skates, and scorpion fishes, including 35 species of fish found only in the waters of the Galapagos.

Have a Question?


Q: What brought you to Steinhart Aquarium?


A: In 1972 every university on the coast wanted an oceanographer. After completing my dissertation at the Scripps Institution of Oceanography, I taught briefly at UC San Diego and then pursued a post-doctoral fellowship in Eastern Australia. While diving off the coast of New Guinea I received a telex: “Steinhart Aquarium director drowns. Position open. Are you interested in a job?” In 1973, I became the youngest guy on the staff, and the head of the staff.

Read all the questions »

More about Dr. McCosker


Department: Aquatic Biology


Expeditions: 24



Steinhart Aquarium Research

Seafood Guide

Dying for a Bowl of Soup

Shark Finning (PDF)



Aquatic biologist John McCosker talks about this elusive fish that was long thought to be the missing link between fish and amphibians.

Life in the Sea
Aquatic biologist John McCosker has seen a change in the public’s perception of the value of life in the water.

Destructive Fishing
Current shrimp fishing techniques are devastating to the ecology of the ocean, warns aquatic biologist John McCosker.

Shark Fin Soup
Will sharks on this planet go extinct because of human stupidity? So asks our shark expert John McCosker.


Selected Publications and Films

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