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Photos, credit US Coast Guard San Francisco

On Wednesday October 16 an aggregation of approximately 20 sharks were observed by two US Coast Guard helicopter patrols.  The Coast Guard helicopter from Station San Francisco reported to Gulf of the Farallones National Marine Sanctuary Media Relation Specialist Mary Jane Schramm that crews observed approximately 20 sharks between 10 and 18 feet off the coast.  When contacted, a US Coast Guard media spokesperson from San Francisco confirmed the sightings between Pacifica and Ocean Beach, approximately 100 yards offshore.

“Although salmon sharks also swim off our coast this time of year and resemble juvenile white sharks, the photos taken from 500 feet indicate they are white sharks. It is impossible to get a frame of reference regarding size from the photographs, so we must rely on the Coast Guard’s estimate of 10-18 feet,” said David McGuire, Director of the San Francisco shark conservation group Shark Stewards.

Scientists refer to the great white shark, carcharodon carcarias, as white sharks. Known as the Northeast Pacific population, the west coast of the United States hosts one of the world’s few aggregation of white sharks.

“White sharks routinely swim off the central California coastline but attacks on humans are extremely rare. An unusual number of juvenile white sharks under 10 feet long have been observed this year, likely associated with the unseasonably high water temperatures along the coast,”adds McGuire. “With 12 miles of coastline covered we would not refer to this as a cluster and certainly not a swarm, as one news reporter put it, but a loose aggregation.”

White sharks do not school, but they do aggregate off feeding zones such as Ano Nuevo and the Farallon Islands. The sharks are scattered over a 10 -12 mile section of the Bay Area coastline.  One photograph shows two sharks separated by hundreds of meters, while others all show individual sharks.

Large sharks are usually offshore at haul outs of seals and sealion like the Farallon Islands, Ano Nuevo or off Drakes Bay, while juveniles tend to be more coastal. A probable sub-adult shark was recorded by camera phone preying on a pinniped inside the San Francisco Bay. Elephant seals and other species of sea lions and seals are the adult sharks favored prey.  This event was unusual because it was inside the bay and recorded, but the predation is natural and common along the coastline. Another predation on a sea lion was observed off Pacifica this summer.

Shark Stewards will be out searching for sharks using drones (where legal) and are making contact with public safety agencies to update the public as we can obtain information on sightings, and using the twitter feed with the #SharkWatch.

Shark Stewards has set up  #Sharkwatch system on twitter so that surfers, kayakers, swimmer or other observers can alert others.  A  project of the California Academy of Sciences and Shark Stewards, observations and a citizen science data base called SharkWatch using the App iNaturalist records observations of sharks along the coast,and the Pacific Coast Shark Research Committee accounts for all verifiable observations, including human encounters.

In early July an aggregation of mostly juvenile white sharks was observed off Sea Cliff State Beach off Aptos CA.  The beach was closed until the sharks were no longer observed and there were no incidents.

“There is no cause for alarm, but there is reason for caution when entering the ocean this time of year.  An 18 foot shark is very large, mature shark and can cause considerable harm to seals or humans, ” said McGuire.  I wont stop enjoying the ocean, but I might swim and surf somewhere else for a few days after a confirmed seal predation or sighting. We do not want to have any accidents.”

Ocean goers are advised to use prudence, obey posted signs and the signs of nature. Other methods of avoiding an encounter with sharks are located on the Shark Stewards website.

Press

Gang Of About 20 Great White Sharks Spotted Off Ocean Beach And Pacifica SFGate
20 GREAT WHITE SHARKS SPOTTED OFF SAN FRAN’S OCEAN BEACH TetonGravity Research
20 great white sharks spotted 100 yards off Northern California coast LA Times
Large cluster of great whites surprises, concerns shark experts SFGATE
Cluster Of 20 Great White Sharks Spotted Swimming Off Pacifica, SF Ocean Beach CBS News
CLUSTER OF GREAT WHITES SPOTTED OFF NORCAL US Coast Guard sees 20 sharks - up to 18 feet - off Pacifica and San Francisco Surfline

Shark Stewrads Pod cast of Interview with Jenny Stock, KWMR Radio http://cordellbank.noaa.gov/education/radiopodcast2015.html

Shark Stewards is a non profit project of The Earth Island Institute
Copyright © *2015* *David McGuire*, All rights reserved.
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