Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Great white shark population in good health along California coast, UF study finds

17.06.2014

The Great White Shark is not endangered in the Eastern North Pacific, and, in fact, is doing well enough that its numbers likely are growing, according to an international research team led by a University of Florida researcher.

George Burgess, director of the Florida Program for Shark Research, said the wide-ranging study is good news for shark conservation. The study, to be published June 16 in the journal PLOS ONE, indicates measures in place to protect the ocean's apex predator are working.

Scientists reanalyzed 3-year-old research that indicated white shark numbers in the Eastern North Pacific were alarmingly low, with only 219 counted at two sites. That study triggered petitions to list white sharks as endangered.

"White sharks are the largest and most charismatic of the predator sharks, and the poster child for sharks and the oceans in general," said Burgess, whose research program is based at the Florida Museum of Natural History on the UF campus. "If something is wrong with the largest, most powerful group in the sea, then something is wrong with the sea, so it's a relief to find they're in good shape."

The National Marine Fisheries Service (NMFS) was petitioned to add white sharks to the endangered species list but declined, based on its own research, bolstered by a preview copy of the study by the international team, said Heidi Dewar, a fisheries research biologist. NMFS estimated the Eastern North Pacific population at about 3,000 sharks.

"We determined there were enough animals that there was a low to very low risk of extinction, and in fact, most developments suggest an increasing population," Dewar said.

Burgess and his colleagues assembled a 10-member team with expertise in all facets of shark biology: demography, population dynamics, life history, tagging and movements, fishery biology and conservation, and mathematical modeling. The team has studied sharks from Florida to California, Alaska to Hawaii, and around the globe.

White sharks can be notoriously difficult to count. They are highly mobile and migratory and group themselves by age, sex and size. Unlike marine mammals, they do not surface to breathe. Some gather at aggregation sites to dine on seals, others stay at sea, dining on fish. Most tagging studies use photographic tags – pictures of unique markings, such as nicks on fins or scars – and those markings can change over time.

Population estimates, however, are important to conservation. Sharks are sensitive to overfishing, both as bycatch for fisherman seeking other fish and as targets for sport or in areas where shark meat is a delicacy. White sharks are protected in many areas internationally, including the west coast of the United States, but because they swim in and out of jurisdictions, they are still vulnerable, and the older study raised concerns.

For their reanalysis, the international team examined the two aggregation sites where the earlier count was obtained, the Farallon Islands and Tomales Point, which attract seals and the sharks that feed on them. They found that the sub-populations at both sites were so fluid, with both resident and transient sharks, that it would not be possible to extrapolate a total population number. To get a better picture of the white shark population in the Eastern North Pacific, the team decided to examine several other known aggregation sites, from Mexico into British Columbia and Alaska.

The team also conducted a demographic analysis to account for all life stages for the sharks at Farallon Islands and Tomales Point and found that the total population is most likely at least an order of magnitude higher – rather than just over 200 sharks there likely were well over 2,000.

"The listing of a species as 'endangered' places substantial demands on governments," Burgess said. "Listing species that are not under the threat of biological extinction diverts resources away from species genuinely at risk. We want to use our resources for the neediest species."

The earlier study also compared shark population numbers with other apex predators, such as polar bears and killer whales. That study, however, ignored the differences in the community structures for those three species and the fact that polar bears and whales, as mammals, are easier to count.

"That we found these sharks are doing OK, better than OK, is a real positive in light of the fact that other shark populations are not necessarily doing as well," said Burgess, a co-founder of the Shark Specialist Group of the International Union for the Conservation of Nature. "We hope others can take our results and use them as a positive starting point for additional investigation."

###

Writer: Cindy Spence, cindyrspence@ufl.edu, 352-846-2573

Source: George Burgess, gburgess@flmnh.ufl.edu, 352-318-3812

George Burgess | Eurek Alert!

More articles from Ecology, The Environment and Conservation:

nachricht Managing an endangered river across the US-Mexico border
18.07.2016 | International Institute for Applied Systems Analysis (IIASA)

nachricht The European pet trade is jeopardising the survival of rare reptile species
13.07.2016 | Helmholtz-Zentrum für Umweltforschung - UFZ

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Self-assembling nano inks form conductive and transparent grids during imprint

Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.

To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...

Im Focus: The Glowing Brain

A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology

On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...

Im Focus: Newly discovered material property may lead to high temp superconductivity

Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.

While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.

Im Focus: Mapping electromagnetic waveforms

Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.

Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...

Im Focus: Continental tug-of-war - until the rope snaps

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

GROWING IN CITIES - Interdisciplinary Perspectives on Urban Gardening

15.07.2016 | Event News

SIGGRAPH2016 Computer Graphics Interactive Techniques, 24-28 July, Anaheim, California

15.07.2016 | Event News

Partner countries of FAIR accelerator meet in Darmstadt and approve developments

11.07.2016 | Event News

 
Latest News

From vision to hand action

26.07.2016 | Life Sciences

Severity of enzyme deficiency central to favism

26.07.2016 | Life Sciences

The Glowing Brain

26.07.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>