Tuesday, April 28, 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

    Yolo Basin Foundation celebrates 25 years, announces major fund drive

    By Felicia Alvarez | From Page: A1 | Gallery

     
    Teens embrace public art through Pence Gallery program

    By Anne Ternus-Bellamy | From Page: A1 | Gallery

    Robotics team members reflect on their big win

    By Kellen Browning | From Page: A1

     
    City’s eco-classes will explore water, wildlife, pests, composting

    By Special to The Enterprise | From Page: A1

    Many hands make light work

    By Enterprise staff | From Page: A1 | Gallery

     
    Capay Organic hosts Cinco de Mayo party

    By Special to The Enterprise | From Page: A3

     
    Yolo County Bar Association honors Magna Carta, probation chief

    By Special to The Enterprise | From Page: A3

    Sierra Club leaders will meet April 30

    By Enterprise staff | From Page: A3

     
    Pedro party, lunch benefit Yolo Hospice

    By Enterprise staff | From Page: A4

     
    Author — injured arm in sling — will sign her new book

    By Jeff Hudson | From Page: A4 | Gallery

    Chicken manure compost class planned

    By Enterprise staff | From Page: A4

     
    Party celebrates release of Lescroart’s new novel

    By Enterprise staff | From Page: A4

    Curious about calculus? Try Barcellos’ new book

    By Special to The Enterprise | From Page: A4

     
    Master Gardeners teach workshops throughout county

    By Enterprise staff | From Page: A4

    Faithful Partner Fund established for K-9 officers

    By Special to The Enterprise | From Page: A4 | Gallery

     
    Vacaville contractor convicted of fraud

    By Enterprise staff | From Page: A5

    Holmes’ Green Team wins state award

    By Special to The Enterprise | From Page: A5 | Gallery

     
    Blueberries, apricots arrive at Sutter market

    By Enterprise staff | From Page: A7 | Gallery

    New UCD art lecture series named for Thiebauds

    By Special to The Enterprise | From Page: A7 | Gallery

     
    Pinball show features lots of free play

    By Enterprise staff | From Page: A7

    Asian garden open for tours this weekend

    By Special to The Enterprise | From Page: A10 | Gallery

     
    .

    Forum

    Waking up to the awful truth

    By Creators Syndicate | From Page: B5

     
    David Brooks: Love and merit

    By David Brooks | From Page: A6

    Davis’ active transportation plan is right on target

    By Special to The Enterprise | From Page: A6

     
    Dog’s freedom isn’t worth it

    By Letters to the Editor | From Page: A6

    Vaccine bill is vital for our health

    By Letters to the Editor | From Page: A6

     
    Thanks for camera’s return

    By Letters to the Editor | From Page: A6

    Tom Meyer cartoon

    By Debbie Davis | From Page: A6

     
    .

    Sports

    Huge first frame lifts DHS to huge baseball win

    By Spencer Ault | From Page: B1 | Gallery

     
    Blue Devil girls run it up on Grant

    By Enterprise staff | From Page: B1

    UCD golfers move into first at Big West Championship

    By Enterprise staff | From Page: B1

     
    Another big inning does in Devil softballers

    By Thomas Oide | From Page: B1

     
    AAA roundup: Cardinals break out big bats in Davis Little League win

    By Enterprise staff | From Page: B3 | Gallery

     
    .

    Features

    .

    Arts

    Get a positive vibe Wednesday from Tha Dirt Feelin’

    By Enterprise staff | From Page: A3 | Gallery

     
    Momentum Dance Company plans spring concert

    By Special to The Enterprise | From Page: A3 | Gallery

    Sacramento Youth Symphony holding open auditions

    By Special to The Enterprise | From Page: A9Comments are off for this post

     
    Winters Theatre Company performs on the Big Day of Giving

    By Enterprise staff | From Page: A9

    There’s no place like home in DMTC’s ‘Wizard of Oz’

    By Bev Sykes | From Page: A9 | Gallery

     
    ‘Contempt of Court’ next up at Winters Theatre Company

    By Special to The Enterprise | From Page: A9

    Have breakfast in Oz on May 16

    By Enterprise staff | From Page: A9

     
    Black Sea Hotel to perform in Village Homes

    By Enterprise staff | From Page: A9

    DMTC’s young performers present a steam-punk ‘Snow White’

    By Special to The Enterprise | From Page: A9 | Gallery

     
    .

    Business

    .

    Obituaries

     
    .

    Comics

    Comics: Tuesday, April 28, 2015 (set 1)

    By Creator | From Page: B5

     
    Comics: Tuesday, April 28, 2015 (set 2)

    By Creator | From Page: B7