LONG BEACH, Calif. — They are arguably the king of the sea, or at least near or at the top of the ocean’s food chain.
The great white shark has been cruising the coast in Southern California for a long time, but local researchers and scientists say they’re unsure what the creature eats. Therefore, a team at Cal State University Long Beach’s Shark Lab is trying to figure out the great white shark’s diet.
What You Need To Know
- CSU Long Beach’s Shark Lab have collected muscle and blood samples from great white sharks to figure out their diets
- The samples are stored in a subzero freezer on campus
- Nitrogen signatures show where in the food chain the shark's diet comes from
- Samples were collected in the summer of 2020
In order to figure out what sharks have been snacking on, researcher Yamilla Samora Chacon starts out by collecting samples. She explained that a team goes out in the ocean with a pole that is similar to what they use when tagging sharks. In order to collect blood and muscle samples, they give the shark what she described as “a tiny poke," similar to spearfishing.
“They don’t feel it," said Chacon.
The samples are then stored in a sub-zero freezer on campus so that they're in "good condition" before the team starts drying them.
Chacon explained that the muscle and blood act like a shark’s food diary. The muscle would be like looking at everything the shark ate for a year.
"Blood cells tend to get regenerated faster than muscle," she said. "So, what we’re going to see in the blood is more recent meals the shark has been consuming."
The samples need to be dried and prepped. Chacon uses a mortar and pestle typically found in a kitchen to crush shark tissue into a fine powder. Once the sample is ready, it gets sent to a lab at the University of California Davis to be analyzed for nitrogen and carbon.
"They’re like common elements and all animals need them to survive," said Chacon. "But they get them from their food."
Chris Lowe, director of Shark Lab Director and marine biology professor, explained that the same process of sampling and processing will also have to be done with potential shark prey, such as stingrays, grunion, and more. He added that each creature has what’s called a stable isotopic signature — a unique mix of carbon and nitrogen.
"So the question is, can we differentiate these different preys?" said Dr. Lowe. "And just like 'you are what you eat,' they are what they eat. So that signature should match what different prey they’re eating. And then that gets incorporated into the white shark.”
Chacon noted that carbon signatures are like GPS, offering a map of places sharks like to eat.
"If we compare a shark that is feeding onshore and offshore, we’re going to get different carbonic signatures," said Chacon, who added that nitrogen signatures offer clues into where in the food chain the shark likes to eat from.
The researchers noted this study may get them closer to figuring out what the great white sharks of Southern California are eating without having to do what some shark researchers in other parts of the world have done — including opening up the shark’s stomach, a method Chacon described as “very invasive, and you have to kill the shark.”
The team will be analyzing great whites of all ages and sizes to compare how their diet changes as they grow. Chacon hopes to have all the samples collected during the summer of 2020 by the upcoming summer.