Tuesday, January 27, 2015
YOLO COUNTY NEWS
99 CENTS

Study finds few white sharks off California coast

A white shark (Carcharodon carcharias) investigates a fake seal decoy used by UC Davis researchers. UC Davis/Courtesy photo

By
March 9, 2011 |

In the first census of its kind, research led by UC Davis and Stanford University found that there are far fewer white sharks off central California than biologists had thought.

The study, published Tuesday in the journal Biology Letters, is the first rigorous scientific estimate of white shark numbers in the northeast Pacific Ocean. It is also the best estimate among the world’s three known white shark populations (the others are in Australia/New Zealand and South Africa).

The researchers went out into the Pacific Ocean in small boats to places where white sharks congregate. They lured the sharks into photo range using a seal-shaped decoy on a fishing line. From 321 photographs of the uniquely jagged edges of white sharks’ dorsal fins, they identified 131 individual sharks.

From these data they used statistical methods to estimate that there are 219 adult and sub-adult white sharks in the region. (White sharks are classed as sub-adults when they reach about 8 to 9 feet in length and their dietary focus shifts from eating fish to mostly marine mammals. They are adults when they reach sexual maturity — for males, that is about 13 feet long; for females, it is about 15 feet.)

“This low number was a real surprise,” said UC Davis doctoral student Taylor Chapple, the study’s lead author. “It’s lower than we expected, and also substantially smaller than populations of other large marine predators, such as killer whales and polar bears. However, this estimate only represents a single point in time; further research will tell us if this number represents a healthy, viable population, or one critically in danger of collapse, or something in between.”

“We’ve found that these white sharks return to the same regions of the coast year after year,” said study co-author Barbara Block, a Stanford University marine biologist and a leading expert on sharks, tunas and billfishes. “It is this fact that makes it possible to estimate their numbers. Our goal is to keep track of our ocean predators.”

Satellite tagging studies have demonstrated that white sharks in the northeast Pacific make annual migrations from coastal areas in Central California and Guadalupe Island, Mexico, out to the Hawaiian Islands or to the “White Shark Cafe,” a region of the open ocean between the Baja Peninsula and Hawaii where white sharks have been found to congregate — and then they return to the coastal areas.

In addition to Block and Chapple (who is now a postdoctoral researcher at the Max Planck Institute in Germany), the study’s co-authors are Loo Botsford, professor, and Peter Klimley, adjunct associate professor, both of the UCD department of wildlife, fish and conservation biology; postdoctoral researcher Salvador Jorgensen of Stanford University (who is now a research scientist with the Monterey Bay Aquarium); researcher Scot Anderson of Point Reyes National Seashore; and graduate student Paul Kanive of Montana State University in Bozeman.

The research was funded by the National Oceanic and Atmospheric Association Fisheries through the Partnership for Education in Marine Resource and Ecosystem Management and the NOAA Fisheries/Sea Grant Fellowship Program; the Gordon and Betty Moore Foundation; the National Park Service’s Pacific Coast Science and Learning Center; Monterey Bay Aquarium; UCD Bodega Marine Laboratory; and Patricia King, a member of the Point Reyes National Seashore Association.

— UC Davis News Service

Comments

comments

  • Recent Posts

  • Enter your email address to subscribe to this newspaper and receive notifications of new articles by email.

  • .

    News

    In vino veritas: A criminal case and intrigue in Napa Valley

    By New York Times News Service | From Page: A1 | Gallery

     
    Interfaith event focuses on justice

    By Fred Gladdis | From Page: A1 | Gallery

    Parking lawsuit may be more than meets the eye

    By Dave Ryan | From Page: A1

     
    Crash leads to DUI, hit-run arrest

    By Lauren Keene | From Page: A2

     
    Blizzard howls its way into Boston

    By The Associated Press | From Page: A2 | Gallery

    New-home sales jump 11.6% in December

    By The Associated Press | From Page: A2

     
    Senate Dems block GOP effort to wind down pipeline debate

    By The Associated Press | From Page: A2

     
    Share your love (story) with us

    By Enterprise staff | From Page: A3

    Pets of the week

    By Enterprise staff | From Page: A3 | Gallery

     
    Winter produce, treats available at Wednesday market

    By Enterprise staff | From Page: A3

    Have a ‘Heart to Heart’ with Dr. G

    By Enterprise staff | From Page: A3

     
    Workshop offers tips on GoPro cameras

    By Enterprise staff | From Page: A3

    Sutter Davis Hospital seeks volunteer doulas

    By Special to The Enterprise | From Page: A3

     
    Apply now for Soroptimist service grants

    By Enterprise staff | From Page: A3

    Apply now to be on Davis’ coop crawl

    By Enterprise staff | From Page: A4

     
    Vote for your favorites in Readers’ Choice poll

    By Enterprise staff | From Page: A4

    Thorp receives UCD’s Distinguished Emeritus Award

    By Kathy Keatley Garvey | From Page: A4 | Gallery

     
    Learn nature photography from an expert

    By Enterprise staff | From Page: A4 | Gallery

    Innovation opportunities on the agenda

    By Enterprise staff | From Page: A4

     
    Storyteller relies on nature as his subject on Saturday

    By Enterprise staff | From Page: A4

    Seed swap set Friday at Davis Cemetery

    By Enterprise staff | From Page: A4

     
    VFW post plans Valentine’s Day Heroes Breakfast

    By Enterprise staff | From Page: A4 | Gallery

    Sutter auxiliary seeks volunteers

    By Enterprise staff | From Page: A5

     
    A winemaker’s downfall

    By New York Times News Service | From Page: A7

    Gerber nominations open now

    By Enterprise staff | From Page: A10

     
    .

    Forum

    Taking turns as the halfway house

    By Creators Syndicate | From Page: B5

     
    Wife’s attitude costs her friends

    By Creators Syndicate | From Page: B5

    A family was torn apart, but we survived

    By Special to The Enterprise | From Page: A6 | Gallery

     
    Damage done to democracy

    By Letters to the Editor | From Page: A6

    It’s foggy? Turn on your headlights

    By Letters to the Editor | From Page: A6

     
    Locals will join march for climate change

    By Michelle Millet | From Page: A6

    .

    Sports

    Aggie women almost get a sweep of Portland tennis teams

    By Enterprise staff | From Page: B1 | Gallery

     
    Four DHS wrestlers soar at McClellan Air Force Base

    By Enterprise staff | From Page: B1

    Anatomy of a hoops collapse: Can Aggie men handle the pressure?

    By Bruce Gallaudet | From Page: B1 | Gallery

     
    UCD women need to get in gear for a basketball road trip

    By Bruce Gallaudet | From Page: B1 | Gallery

    UCD swims past Santa Barbara

    By Enterprise staff | From Page: B2 | Gallery

     
    Sports briefs: Eat ribs for the Davis Aquadarts

    By Enterprise staff | From Page: B8

    .

    Features

    Name Droppers: Lea Rosenberg leads Odd Fellows

    By Enterprise staff | From Page: A5

     
    .

    Arts

    Wynonna Judd will perform Feb. 13 in Vacaville

    By Enterprise staff | From Page: A9

     
    DHS Idol finals will be a tough competition

    By Krystal Lau | From Page: A9

     
    ‘Ideation’ a funny, dark, thrilling farce — and more

    By Bev Sykes | From Page: A9 | Gallery

    .

    Business

    .

    Obituaries

    Death notice: Lorraine Bernice DeGraff

    By Special to The Enterprise | From Page: A2

     
    .

    Comics

    Comics: Tuesday, January 27, 2015 (set 1)

    By Creator | From Page: B5

     
    Comics: Tuesday, January 27, 2015 (set 2)

    By Creator | From Page: B7