(Photo: Rob Stewart/Oceana )
A new study says sharks are necessary for healthy oceans, but commercial fishing is taking a toll on their populations. Each year, tens of millions of sharks are caught only for their fins. KPBS Environmental Reporter Ed Joyce spoke with a marine biologist at the Scripps Institution of Oceanography about the role of sharks in the ocean ecosystem.
Sharks have been swimming in the world's oceans before dinosaurs roamed the Earth. But whether they're still around in the next century is in doubt.
The group Oceana has a new report that says sharks are key players in keeping oceans healthy. Stuart Sandin is a marine biologist at UCSD's Scripps Institution of Oceanography.
Sandin: Sharks by and large are the top predators in most marine ecosystems. And what we know is that predators serve a unique role. They minimize the incidence of disease of prey species. There's no reason to believe that sharks, as top predators are in terrestrial systems.
The Oceana study says some shark species are now in danger of extinction. Sandin says that's because sharks have been exploited for decades - and we're seeing the results now.
Sandin: We as a human society are starting to exploit the center of the ocean right now. The last areas that have healthy populations of sharks and these are now under threat as well.
The Oceana report says humans kill more than 100 million sharks worldwide each year. And the practice of shark finning alone kills 26 to 73 million sharks a year.
Because a bowl of shark fin soup can cost up to $100, the fins are prized, but Sandin says that comes at a higher price for sharks.
Sandin: The harvest for wasting the entire meat of that animal -- what it allows a fishing boat to do is to kill a lot more sharks than it actually uses.
He says while more research is needed into the importance of sharks, they need protection now.
Sandin: What we need is something that's analagous to the national park system in the United States. Large areas of coastal environments that are protected from fishing, that we don't kill sharks that we don't want.
Sandin says there are two facts he'd like us to keep in mind about sharks.
Sandin: For that reason alone it seems conservative and important to protect them -- to remove them from the entire planet without understanding yet what they've done and what their role used to be.
When people think about sharks, the predatory great white gets a lot of attention, but there are 350 shark species -- and most of them are not after humans.
Sandin: The myth of a shark as a beast that will only kill people is something of a myth -- the majority of sharks the sharks feed lower on the food chain the sharks interact with me more like they're dogs, curious dogs, then like a vicious predator that has anything out for me. The majority of experiences that people have with sharks are very similar.
Many of us have snorkeled or gone on dive trips to swim with nurse sharks or leopard sharks - and Sandin says, like most shark species, they're not threatening.
Sandin: Here in San Diego one of the best activities... La Jolla Cove and look at the aggregation of leopard sharks. They're just beautiful animals and have no negative impacts on people.
Doctor Stuart Sandin is a marine biologist at the Scripps Institution of Oceanography in San Diego.
The new report from Oceana is called "Predators as Prey - why healthy oceans need sharks."
Ed Joyce, KPBS News.
