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, firstname.lastname@example.org, 352-846-2573
Source: George Burgess, email@example.com, 352-318-3812
George Burgess | Eurek Alert!
Hunting pressure on forest animals in Africa is on the increase
09.02.2016 | Goethe-Universität Frankfurt am Main
Man-made underwater sound may have wider ecosystem effects than previously thought
05.02.2016 | University of Southampton
Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.
The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
09.02.2016 | Event News
02.02.2016 | Event News
26.01.2016 | Event News
11.02.2016 | Life Sciences
11.02.2016 | Physics and Astronomy
11.02.2016 | Earth Sciences