Research Shows How Fishing for Sharks Also Affects Other Sea Animals
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This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein. And I'm Steve Ember. On our program this week, we will tell how fishing for sharks may affect other sea animals. We will also tell about a newly identified large cat and warnings for drugs to treat sleep disorders. And, we will report on a proposed system for measuring harmful substances.
Several recent studies have linked human activities to reduced numbers of sharks in the world's oceans. Scientists now say a sharp decrease in the number of large sharks in the Atlantic Ocean has helped some kinds of fish. They say such fish are now threatening other sea animals.
Canadian and American scientists studied the effects of people fishing for sharks in the Northwest Atlantic over the past thirty-five years. Results of their studies were published in Science magazine.
The scientists say one effect of shark fishing has been an estimated ninety-nine percent decrease in some shark populations. They say the loss of larger sharks has caused a population explosion among fish like skates and rays. Such fish and smaller sharks have increased in number along the east coast of the United States.
Sharks usually eat skates and rays. The scientists say these fish feed on shellfish, which are disappearing from the ocean. They say other sea animals are also being threatened by the area's changing environment.
Demand for shark fins has been rising in Asia. Shark fins are used for medical purposes and also for food. The popularity of shark-fin soup in China has made the demand for these animals greater.
For one of the studies, scientists from Canada examined information from private fishing companies and other research projects. They noted a sharp decrease in eleven kinds of great sharks since the nineteen-eighties.
One of the scientists was Julia Baum of Dalhousie University. She says the World Conservation Union earlier this year listed great hammerhead and scalloped hammerhead sharks as being in danger of disappearing. The group also reported the dusky and sandbar sharks as being threatened.
Other scientists agree that the shark population decrease may be linked to the increase of smaller fish. But they say the decrease in sharks is not the only cause. They debate how much the decrease has affected other fish species. Other theories for these changes include pollution and loss of native waters for some animals.
Environmental activists recently announced the discovery of a new kind of clouded leopard. The wildlife group W.W.F. says the new species is found on the Southeast Asian islands of Borneo and Sumatra.
Until now, the clouded leopards there were believed to be the same as those living on the Asian mainland. Yet tests of genetic material show the animals are, in fact, very different. The two species of clouded leopard also have physical differences. Scientists found they have different markings, and different colors over their skin.
The Bornean clouded leopard is the largest animal hunter on Borneo. On Sumatra, only the Sumatran tiger is larger. The new species of clouded leopard has the longest canine teeth for its size of any cat. It hunts lizards, monkeys, and small deer.
Researchers believe the clouded leopard of Borneo may have separated from the mainland population more than one million years ago. Genetic tests have shown about forty differences between the two species.
Researchers estimate that between five thousand and eleven thousand clouded leopards live in the rain forest called the Heart of Borneo.
Stuart Chapman is the W.W.F. international coordinator for the Heart of Borneo program. The program is aimed at protecting plant and animal life in on the island. Mr. Chapman says biologists have seen the clouded leopard of Borneo for more than a century and not known it was different. He says identification of the new species shows the importance of protecting the Heart of Borneo. The biggest threat to these large cats is the destruction of the areas where they live.
The discovery of the clouded leopard comes weeks after the W.W.F. reported that scientists had identified at least fifty-two new plant and animals species on Borneo.
A British study has found that alcohol and tobacco products are more dangerous than some illegal substances. The study identified alcoholic drinks and tobacco as more harmful than illegal drugs like marijuana or ecstasy.
David Nutt of Bristol University in Britain and other researchers produced the study. They proposed a system for listing harmful substances. The system is based on evidence of the harm created for the user and for other people. Results of the study were published in The Lancet magazine.
The researchers proposed three ways to measure the possible harm that a substance causes. The first measure is the physical harm to the user. The second is the ability of the drug to create a sense of dependence in the user. The third is the effect of a drug's use on the community.
The researchers asked two groups of experts to create lists of the most dangerous drugs. The experts included psychiatrists who study drug dependence, and legal or police officials with scientific knowledge. The experts were asked to consider twenty drugs, including cocaine, ecstasy, and heroin. Study organizers then combined the two lists to create general ratings of each substance.
The experts generally agreed with each other. However, they did not agree with Britain's current rating system for dangerous substances.
The experts agreed that the most dangerous of the twenty substances was heroin. Cocaine was the second most dangerous. Drinking alcohol was the fifth-most harmful on the combined lists. Smoking tobacco was ninth on the combined lists. Marijuana was eleventh. And, ecstasy was near the bottom of the list.
Professor Nutt says he hopes that the study will create a debate within Britain and other areas about how these drugs should be controlled.
The United States Food and Drug Administration has ordered companies to place strong warnings on thirteen drugs that treat sleep disorders. It also ordered the makers of the sleeping drugs to provide information for patients explaining how to safely use the pills.
The F.D.A. announced in March that some of the drugs can have unexpected and dangerous effects. These include the risk of life-threatening allergic reactions. They also include rare incidents of strange behavior. These include people cooking food, eating and even driving while asleep. The patients later had no memory of doing these activities while asleep.
Last year, a member of the United States Congress said he had a sleep-driving incident. Patrick Kennedy, a representative from Rhode Island, crashed his car into a security barrier near the building where lawmakers meet. The accident happened in the middle of the night and no one was hurt. Mr. Kennedy said he had earlier taken a sleep medicine. He asaid he was also being treated with a stomach sickness drug that can cause sleepiness.
A Food and Drug Administration official said the serious side effects of sleep disorder drugs appear to be rare. But, he also said there are probably more cases than are reported. He said the agency believes the risk of such behaviors could be reduced if people take the drugs as directed and do not drink alcohol while taking the drugs.
This SCIENCE IN THE NEWS program was written by Caty Weaver and Brianna Blake, who also was our producer. I'm Steve Ember. And I'm Barbara Klein. Join us again next week for more news about science in Special English on the Voice of America.