89 F
Davis

Davis, California

Wednesday, August 4, 2021

What sharp teeth you have

“Everybody calls me Dr. Hammerhead,” said Peter Klimley.

Klimley’s proud of his nickname, and he should be. He earned it.

Klimley has traveled the world to study sharks. In 2003, he wrote a book called The Secret Life of Sharks. And today he works as a professor of wildlife, fish and conservation biology at UC Davis.

“Hammerheads are the Ph.D.’s of the shark world,” he said. “I was the first person to get in the water and study their behavior.”

I heard of Klimley when I read a recent report out of UC Davis estimating the number of great white sharks off the central coast of California. Klimley was an adviser to the report’s primary author, Taylor Chapple. While studying animal behavior is important, Chapple and Klimley wanted to know the actual population size.

“People didn’t really know how many there were, so they would pick out of a hat the number 500 or so,” Klimley said.

Turns out there are only about 219 sharks off our coast.

“I think what we’re seeing is the last of their kind,” said Patric Douglas, CEO of Shark Diver, a commercial company that leads shark-watching expeditions.

Douglas is not a scientist, but several years ago, he worked with Klimley to establish a shark-tagging program where scientists and eco-tourism businesses work together. Douglas called the 219 estimate “frightening.”

“I thought the population was more like 1,000 animals,” Douglas said.

Because scientists didn’t know the great white population before now, Klimley couldn’t say whether 219 was a frightening number, but he did explain why sharks are in danger.

Weirdly, evolution actually seems to have hurt their ability to survive.

Sharks are what are called “apex” predators. That means they are at the top of the food chain. But Klimley said it is important to look at predator/prey relationships as less of a chain and more of a “pyramid.” On land, there are typically three levels of the pyramid, and there are fewer organisms on each level. This pyramid goes something like grass then elk then wolf.

The ocean is a different sort of ecosystem because there are many more pyramid levels; In the waters off California, zooplankton eat phytoplankton, small fish eat zooplankton, sea lions eat small fish and great white sharks eat sea lions. If the pyramid were this tall on land, then bears would eat wolves.

Because there is less food at each level of the pyramid, sharks have to compete for their meals. One way of making sure food is available is for sharks to reproduce slowly and keep the population down. Klimley said it takes great white sharks between 10 and 12 years to be able to reach maturity, and female sharks have only five to nine offspring.

This slow-and-steady system worked for millions of years – until humans arrived.

According to Klimley, shark pups are very vulnerable to fishing. They are either caught for their meat or tangled up in nets meant for other species.

“We need to concentrate on eating species that grow quickly,” said Klimley. “Sharks are not those species.”

Klimley and Douglas think that the more people learn about those 219 sharks off the central California coast, the more people will care about conservation.

“Let’s get busy and get the word out,” Douglas said.

Klimley believes programs like “Shark Week” have already given sharks a celebrity status.

“That may, in the end, by the very reason these sharks survive,” Klimley said.

MADELINE McCURRY-SCHMIDT hopes she never sees a bear eating a wolf. That is definitely the 37th sign of the apocalypse. If you’ve witnessed the end of times, e-mail Madeline at science@theaggie.org.

LEAVE A REPLY

Please enter your comment!
Please enter your name here