New Science Paints Picture of Salmon Shark Diet - NBC Bay Area

New Science Paints Picture of Salmon Shark Diet

New Science Paints Picture of Salmon Shark Diet
Joe Rosato Jr.
Stanford researcher Aaron Carlisle looks at a picture of a salmon shark on his computer inside the Hopkins Marine Station in Monterey. December 2014

If you hear a snippet of the ominous musical score from the film Jaws, you probably won't conjure up an image of a salmon shark.

In fact, there’s a good chance you’ve never even heard of a salmon shark.

But this lesser-known cousin of the famous white shark is out there - indeed munching on salmon - following some unknown trajectory between California and Japan.  

“Until relatively recently, it’s been pretty poorly studied,” said Aaron Carlisle, a researcher with  Stanford University's Hopkins Marine Station in Monterey. “Salmon sharks just for some reason kind of fell through the cracks.”

Salmon shark vertebrae under study at Stanford University's Hopkins Marine Station. December 2014
Photo credit: Joe Rosato Jr.

It’s not to say these sharks were basking in complete obscurity; they’re fished in Alaska where they turn up each year to dine on an endless salmon smorgasbord. But Carlisle and other marine researchers wanted to know more about these creatures and their travels.

Carlisle and his team have now turned to an experimental process in which isotopes are taken of the sharks’ vertebrae which hold bands of information, kind of like the rings of a tree. By tracing the bands, scientists can see what the sharks ate during each year of their life, which in turn revealed where they ate it.

 “If you eat a squid in California,” said Carlisle, “that looks different than the same kind of squid in Alaska.”

Through the testing, the research revealed some sharks which visited Alaska, turned up at the back door of the research center - in the Monterey Bay. They also visit Hawaii and Baja.

The team is using the isotope track in conjunction with traditional electronic tagging to get a more elaborate picture of the sharks’ travels.

“What’s really becoming cutting edge,” said Hopkins research coordinator Steve Litvin, “is using these advanced techniques together to give us much deeper knowledge than we ever could with only one.”

Researchers at Stanford may try using the isotope tracing with other marine life, including white sharks.

The information gleaned about the sharks could be used by fishery managers to set regulations to protect the shark, like continuing bans on gill nets in some areas salmon sharks frequent.

“If you actually want to conserve and manage the population,” Carlisle said, “what you really need to understand is the survival.”
 

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