The mysterious sharks of SF Bay

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It's the San Francisco Ocean Film Festival, which consists of three days of movies on everything from surfing to saving the seas.

Bay area filmmaker /*David McGuire*/ has traveled all over the world photographing and learning about sharks.

He took video in the Pacific Remote Islands. David's latest film is set at home in the San Francisco Bay -- It's called "City of the Shark."

Sharks have a reputation for being aggressive, but David says most are not. Great white sharks no longer live in the bay, and the species that do are actually rather shy.

"There's a large population of sharks in the San Francisco Bay, yet they are difficult to study, they are hard to see and we don't know how many there are," said McGuire.

David shot the film in partnership with the /*Aquarium of the Bay Foundation*/, which has launched a major research project to learn more about bay sharks.

Sharks all over the world are facing serious threats from over fishing and water pollution. So scientists want to know how our local sharks are doing.

"I think there's reason to be concerned about all sharks. I mean generally speaking, their numbers are declining at an unbelievable rate," said Christina Slager from Aquarium of the Bay.

The shark film documents research being done on the Sevengill - the largest shark in the bay.

Scientists want to know more about the Sevengill sharks' habits, and how they use the bay. So researchers from the aquarium and UC Davis are implanting transmitters to track the sharks' movements.

The film follows the entire procedure, up until the shark is released and the transmitter starts working.

The research project is only a few months old, so it will be a while before scientists have anything definite to report. In the meantime, they're hoping this film will remind people about the critical part sharks play in the food-web.

"When you remove sharks from the system, the system has this cascade effect where it eventually degrades, and it becomes unhealthy. So having sharks in the ocean is really important because they maintain a healthy ocean," said McGuire.

The City of the Shark is just one of 35 documentaries, fictional and animated films in this year's /*San Francisco Ocean Film Festival*/. There will also be in-depth panel discussions about issues that affect the ocean.

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