Elephant Seal News

Buoy deployed to detect sharks near elephant seal colony

Special to The CambrianOctober 21, 2013 

A shark-tracking buoy was deployed by, from left, Capt. Mark Tognazzini of the The Bonnie Marietta, scientist Taylor Chapple, Ph.D., and first-mate Bill Skok.


Friends of the Elephant Seal recently teamed with researchers from Hopkins Marine Station to deploy a buoy off Piedras Blancas to track tagged white sharks near the elephant seal rookery about 12 miles north of Cambria.

The Stanford University researchers have been tagging and tracking white sharks for more than a decade. Led by Dr. Barbara Block, they are working to create a “Wired Ocean” to track and monitor sharks in real-time.

The buoy, deployed on Saturday, Oct. 12, can detect any of the 100-plus white sharks that Block's team has tagged off the California coast if they enter the area around Piedras Blancas. The information will be linked with the free iOS app Shark Net to bring the information to the public.

The buoy is part of a array of buoys positioned near Point Reyes, the Farallons, Año Nuevo and now Piedras Blancas as part of the Global Tagging of Pelagic Predators project.

White sharks are one of the primary predators of elephant seals. Because of the interest in the risks to elephant seals at Piedras Blancas, Friends of the Elephant Seal donated funds for the equipment installed here. The project was carried out in consultation with California State Parks.

While we have rarely seen evidence of sharks in the area, their presence is of considerable concern to visitors to the seal rookery. The experience at the Farallon elephant seal rookery is that the shark population began a significant increase 20 years after the first seals came there. That rookery, Point Reyes and Año Nuevo define a region known as the “Red Triangle” because of the high number of sharks in the area.

From 1991 to 2010 the number of pups born in those rookeries did not change from its 1991 count of 2,700. Over that same time span, the number of pups born at Piedras Blancas grew from 0 to 4,300 and on Santa Rosa, San Miguel and San Nicholas Islands the count grew from 16,100 to 33,100. The density of sharks near the rookery appears to be a very important factor in the prosperity of a rookery.

The buoy off Piedras Blancas will detect a shark’s location within 4 feet and transmit the detection immediately to a satellite and to Friends of the Elephant Seal. This will help in finding out how often tagged white sharks are patrolling the area.

The buoy was installed from Capt. Mark Tognazzini’s boat The Bonnie Marietta out of Morro Bay. Tognazzini has more than three decades of experience in commercial and passenger fishing and ocean research. He holds a U.S. Coast Guard Masters license, is trained in emergency response and holds certification in sea survival training.

Joan Crowder’s Elephant Seal News column is special to The Cambrian. Friends of the Elephant Seal is a nonprofit organization dedicated to educating people about elephant seals. For details, call 924-1628 or visit www.elephantseal.org.

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