欢迎北师大版的教师们踊跃上传自己的课件、教案、辅导资料、练习题、单元测试题等教学资料，让我们共同创建一个教学资料的共享空间。
本版管理员：Sophie QQ: 346903996
Overfishing is Emptying World's Rivers, Lakes, Experts Warn
Ocean species such as cod, dolphins, and sea turtles have been grabbing headlines as victims of unsustainable fishing.
But policymakers and the media are neglecting freshwater rivers and lakes that are also being emptied of fish, a new report warns.
Scientists say exploitation of fish stocks is threatening biodiversity in fresh waters globally while also putting jobs and food supplies in developing nations at risk.
"Overfishing of inland waters is a neglected crisis," said the report's co-author Kirk Winemiller, a fish researcher at the Texas Agricultural Experiment Station in College Station.
"Most of the focus is on oceans, with inland waters rarely mentioned," he added. "Yet fish from inland waters are more threatened than those in oceans."
Rivers and lakes highlighted in the report, published today in the journal BioScience, include the Mekong River in Southeast Asia.
The river is home to the Mekong giant catfish—believed to be the world's largest freshwater fish—and various other huge but increasingly threatened species.
Other critically endangered fish cited in the study include the Murray cod of the Murray River Basin in Australia and the lake sturgeon in the Great Lakes of North America.
Fourfold Increase
The report reveals that humans are fishing their way through different-size fish, starting with the largest, then targeting progressively smaller species until there's nothing left to catch.
"Tens of millions of people in developing countries fish inland waters for food and to earn a living," Winemiller said. "Typically fishing pressure shifts from species to species as preferred types or those more easily captured decline in number."
The report stresses the need for government agencies and fisheries experts to work with local people to manage "critically harvested" waters.
The authors say overall harvest from the world's lakes and rivers has quadrupled since 1950. The current catch is estimated at around 8.5 tons (8.7 million metric tons) annually. That figure doesn't include fish taken by anglers, which often go unrecorded.
Two-thirds of the total catch is taken in Asia, with China alone home to some 12 million fishermen.
Average yearly fish consumption in the Mekong Basin in Southeast Asia is estimated at 123 pounds (56 kilograms) per person. Items on the menu include some of world's largest and rarest river fish, including the Mekong giant catfish, freshwater whipray, and giant barb.
Zeb Hogan, a fish biologist at the University of Wisconsin at Madison and a National Geographic Society emerging explorer, has been collecting data on these fish in Cambodia and Thailand.
Hogan says catches of the legendary Mekong giant catfish, which can grow to 660 pounds (300 kilograms) and 9 feet (2.7 meters) in length, have fallen drastically in recent years—from 60 in 1995 to just 4 in 2005.
"There may be a season soon when no fish are caught," he said.
The researcher says there is currently no comprehensive conservation strategy to save these fish from extinction.
He says priorities should include sustainable catch limits for rare Mekong species and the creation of freshwater protected areas.
"Environmental education is also very important," Hogan added. "Few people know about the endangered animals of the Mekong or how important fish are to the livelihoods of people living within the basin.
"Had a coordinated effort been undertaken a decade ago, the situation would not be so dire."
Diminishing Returns
The report says big fish are particularly vulnerable to being captured in nets, and the global trend in overfished waters is towards fish of ever diminishing size.
"Large adult fish are the broodstock that sustains the population," said David Allan, lead author of the report and a conservation biology professor at the University of Michigan in Ann Arbor.
"[Fertility] increases with body size, so large females are especially important reproductively."
And as populations of bigger fish dwindle, smaller species take their place. The Queme River in Benin, West Africa, has seen large predatory fish like the Nile perch replaced by small species of cichlids and catfish.
Allan says fishermen lower their targets accordingly to fill their nets, using smaller mesh sizes to catch the fish that are available.
Depleted fish stocks can have serious repercussions on freshwater ecosystems. The researchers point to the example of waters in western Canada and Alaska where the rotting bodies of Pacific salmon, which die after breeding, provide vital nutrients.
"As salmon populations have decreased because of overfishing and other causes, declines have also occurred in lake productivity and juvenile salmon recruitment," the authors state.
They also warn that overfishing has the potential for severe impacts on human health, especially in developing nations.
For example, increased incidence of schistosomiasis in Africa has been linked to declines of fish species that eat the snails carrying the disease-causing parasites.
欢迎北师大版的教师们踊跃上传自己的课件、教案、辅导资料、练习题、单元测试题等教学资料，让我们共同创建一个教学资料的共享空间。
本版管理员：Sophie QQ: 346903996
Outbreak of red tide kills 300 000 fish in Seto Sea, Japan (Yomiuri Shimbun, 24 Jul 2004) An outbreak of red tide in the Seto Inland Sea off Ehime, Kagawa and Hiroshima prefectures has killed about 300 000 fish, including red sea bream and flatfish, it was learned Thursday (22 July 2004).
The outbreak also has upset the timing of tides in the area, local government officials said.
The phytoplankton Chattonella ovata, which causes the red tide, was collected for the first time off the Utsumicho district of Fukuyama, where red tide also has been reported. In the fish farms around the area, about 25 000 flatfish -- worth about 17 million yen [~ US$155,000] -- have died.
The same plankton was found off Takuma, Kagawa Prefecture, where about 18,000 yellowtail, worth 26.1 million yen [~ US$238,000], have died.
A different type of phytoplankton began to spread in the eastern area of Kitanada Bay off Tsushima, Ehime Prefecture, around 12 Jul 2004. The red tide outbreak there now covers about 1 kilometer and has killed about 250,000 red sea bream, worth about 121.5 million yen [~ US$1.1 million], being raised by the Kitanada Fishery Association.
As the bloom season drops off, we are having to go further afield to get news of blooms. There is a lot going it seems:
From the Philippine Star, 23 May 2000, by Mayen Jaymalin
The Philippines Department of Health (DOH) cautioned the public yesterday against eating shellfish as toxic red tide organisms have once again been detected in Manila Bay.
Dr. Eric Tayag, chief of the DOH-Infectious Disease Control Service, said eating shellfish may lead to red tide poisoning, which is common from May to August. "These are the months when toxic organisms usually breed," Tayag said. "There is still no ban on Manila [shellfish], but we are urging the public to take caution in eating shellfish products during these months."
Results of monitoring by the Bureau of Fisheries and Aquatic Resources (BFAR) showed the presence of the red tide organism, Pyrodinium bahamense, in portions of Manila Bay in Bataan, Cavite and Navotas. Densities of toxic red tide organisms in the water and shellfish gathered from these areas, however, remained within the tolerable level. A red tide shellfish ban is imposed when the organism density is 500 cells per liter of sea water, and when the red tide toxin level is 40 micrograms per 100 grams of shellfish meat.
The BFAR has already imposed a ban in Balite Bay, Davao Oriental as shellfish harvested there revealed a toxicity level of 46 micrograms per 100 grams of shellfish meat.
Red tide has closed shellfishing beds in Eastham and Orleans, Cape Cod, Massachussetts, USA
An outbreak of potentially toxic red tide has closed all shellfishing beds in Eastham and Orleans. Michael Hickey, chief shellfish biologist for the
state Division of Marine Fisheries, said Wednesday the beds will remain closed until at least Tuesday.
Hickey said the levels found in samples taken Tuesday showed 118 micrograms of the toxin per 100 grams of mussel meat. State regulations require closures when toxin levels reach 80 micrograms. Hickey said the algae producing the toxin normally show up later in the spring, when water and air temperatures are on the rise. He said the Cape Cod red tide is the first he has heard of anywhere in New England this year. The closure only affects bivalves mussels, clams, quahogs, oysters and scallops. Lobsters, crabs and shrimp are not subject to the closure.
China Facing Growing Impact of Red Tides
China has been experiencing increasing red tides off the Chinese coast since the 1990s due to increasing pollution caused by industrial waste
water, according to an official report. During the past decade, a total of 200 red tides have been registered and over the past three years there had been 45 major red tides, causing 240 million U.S. dollars in direct economic losses, the recently issued annual report by the State Oceanic Administration of China said.
The report predicts that about 20 to 30 red tides are expected to occur this year in the coastal sea waters, compared with 19 last year. The report
is based on the results of China's largest survey of 2.68 million sq. km of sea waters under its jurisdiction.
The 45 major red tides occurred in the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea. Most of them took place in the seas off the coasts of Guangdong, Shandong, Zhejiang and Liaoning provinces and Shanghai. About 4 billion tons of industrial waste water are discharged annually into the sea, resulting in the accumulation of organic pollutants blamed for the growing outbreaks of disastrous red tides, the administration said. Red tides may also destroy marine lives and bring harm to marine cultivation industries.
China has monitored a large red tide spotted last week off the coast of east China's Zhejiang Province, the first discovered this year in Chinese
waters. The red tide covered 1000 sq. km in the Zhoushan area between the north latitude of 28 and 29 degrees.
Cape Town mussels killed and can kill
The white mussels that washed out at Bloubergstrand this week died after being paralyzed by red tide toxins. Marine and Coastal Management (MCM) staff have warned the public not to eat any shellfish on the West Coast from Cape Point northwards as they may also be poisonous.
MCM marine scientist Trevor Probyn said they had run tests on some of the dead mussels, known as otter mussels, and had found the
dinoflagellate Alexandrium catenella in them. "This is the bad one, the red tide toxin [presumably saxitoxins] causes paralysis and has been known to kill humans. Shellfish are fairly resistant to it, but some are susceptible. What might have happened is the toxin weakened them or paralyzed them and when they were washed out by waves in stormy weather, they could not burrow back into the sand," he said.
Source: The Boston Globe and Associated Press 2 June 2000 [edited]
The first major onset of red tide in 7 years has closed all of southern Maine's clam flats, and officials say the ban could last through the first
month of the state's prime tourism season. The state closed flats from Kittery to just south of Pine Point in Scarborough earlier this week, then
extended the ban to Small Point in Phippsburg.
In red tide, a kind of algae bloom releases toxins known as paralytic shellfish poison. It is unclear what causes the algae blooms. The state has
found amounts of paralytic shellfish poison at more than 100 times the allowable level, according to John Hurst, director of biotoxin monitoring
of the Department of Marine Resources. It will be several weeks before the algae blooms dissipate and the shellfish purge themselves of the toxin, he said.
If ingested by people, the toxin can cause vomiting and tingling sensations in fingers and can be fatal if the level of toxins is high. Lobster and
other fish are considered safe to eat because red tide doesn't affect them. About 1,500 people hold commercial clamming licenses in Maine. They harvest about $10 million worth of clams annually, making clams Maine's fourth most valuable seafood species.
"These guys who make a living from it are going to be hard pressed," said Dave Corbeau, Scarborough's shellfish warden and harbor master. He said he will patrol the beds at night because he fears some people will try digging despite the ban. Clam lovers most likely will find their seafood of choice has become expensive and hard to get.
"The price is going to go sky-high," said Richard Lamontagne, manager of the Clambake Restaurant at Pine Point. "We'll have to go to upstate Maine." He said he will pass the cost on to his customers and use frozen clams.
The Harbor Fish Market in Portland probably won't be selling clams at all, according to Ben Alfiero, one of the owners.
Red tide caused a 5-week closure of clam flats in Maine in 1993.
课件22张PPT。Protecting the Sea Unit 1 Lesson 2I am sailingDiscussion2.What do you think are the causes of
sea pollution?3.What are the solutions to the problem?1. What is sea pollution?Key words:pollute, pollution, over-fishing,
industrial waste,
agricultural waste,
plastic, oil, chemicals, rubbish, ban,
deal with a problemWhat’s the subject of zhi Hong’s
science project?What are the problems about?the first part It is about protecting the sea.First, there's . Second, there's .pollutionover-fishingthe second part What causes over-fishing?Are there more fishermen catching more fish?That's when people fish and the number of fish too low. Some fish may disappear .too muchfallsaltogetherthey hope to catch more fish, but there are less fish to catch.the third part What causes pollution?All sorts: chemicals, , , oil; most of them come from agricultural and waste. plasticrubbishindustrialWhat solutions does government do to pollution?Government departments look for ways to pollution, keep a record
of of pollution, finding where it comes from , people who have broken the law. reducelevelspunishingthe fourth partThe government tries to the number of that people can catch.
They also try to people to get other kinds of .What solutions for over-fishing?controlfish helpjobsthe fifth part1.Really?2.Do you mean3. It sounds like4. Are they?5. Yes , I suppose it must be.6. That’s a good idea!Q5Fang zhou is asking Zhi Hong about her science project.
FZ: Hey, Zhi hong, what did you do for your science project?
ZH: I did something about protecting the sea.
FZ: Protecting the sea from what?
ZH: Well, first, there's pollution. That's big problem. And second, there's over-fishing.FZ: What's over-fishing?
ZH: That's when people fish too much and the number of fish falls too low. Some fish may disappear altogether.
FZ: Really?
ZH: Yes, now there are too many fishermen fishing in the same place.
FZ: Do you mean that there are more fishermen now than there were before?
ZH: Yes, there are many more. And fishermen today have better technology so they can catch more fish than before.
FZ: So there are more fishermen catching more fish?
ZH: Well, they hope to catch more fish, but there are less fish to catch, so they simply can't.
FZ: That's bad.
ZH: Yes, ZH: Yes, and pollution is very bad,too.
FZ: What causes pollution?
ZH: All sorts: chemicals, plastic, rubbish, oil; most of them come from industrial and agricultural waste.
FZ: It sounds like a big problem.
ZH: Yes, it is a big problem.
FZ: How have these two problems been handled?
ZH: Well, some government departments are trying to deal with the situation.
FZ: Are they?
ZH: Yes, some look for ways to reduce pollution, some keep a record of levels of pollution, other departments are responsible for finding where it comes from and punishing people who have broken the law by causing pollution. Of course, often it's quite difficult to find who's responsible for pollution.
FZ: Yes, I suppose it must be.FZ: What about over-fishing? What can be done about that?
ZH: The government tries to control the number of fish that people can catch. In the worst areas they ban fishing completely for a few months at a time so that the fish numbers can grow again. They also try to help people to get other kinds of jobs so there are less people trying to make a living from fishing.
FZ: That’s a good idea!
ZH: Let’s hope it works.pollutionIndustrial waste plasticoilrubbishban课件31张PPT。北师大版
高中一年级(上)
Unit 7Unit 7 The Sea26 Protecting the SeaHow is the sea important to people?People can get sea food such as: fish , sea animals and plants; The sea is rich in many natural resources. we can get oil, natural gas and some metals, besides, the sea has a great effect on climate on the earth.Japanese ship are killing the whale .How cruel they are!!!The sea is important to us. But with the development of society, human beings explore and seize the sea without limit, as a result, do harm to the sea.over-fishingHarvest fish now ,What about the future?What happened?The oil tanker was upset, oil poured into the sea.What is the result?Who can save the poor birds? In 1989 an oil tanker hit a rock off the northwest coast of Alaska. 35,000 tons of oil poured into the sea. The accident was one of the worst in history. More than 34,000 birds and 10.000 animals were killed. 4,8oo square kilometers of ocean were polluted.The Sea is weepingWhat will happen?industrial wastered tideIs there nothing with us? China has been experiencing increasing red tides off the Chinese coast since the 1990s due to increasing pollution caused by industrial waste.
According to an official report, during the past 20 years , a total of 200 red tides have been registered（经正式鉴定的）causing 240 million U.S. dollars in direct economic losses. The 45 major red tides occurred in the Bohai Sea, the Yellow Sea, the EastChina Sea and the South China Sea. About 4 billion tons of industrial waste water are discharged(排放) into the sea every year , resulting in the accumulation（积累）of organic pollutants blamed（归咎于有机污染物） for the growing outbreaks of disastrous red tides. Red tides may also destroy marine lives（海洋生物） and bring harm to marine cultivation industries(海洋养殖业).1. You are likely to notice something about sea pollution in your city or hometown, please talk about it . 2. If we go on polluting the sea what is the result? If the government go on allowing the industrial waste from factories into the sea and rivers, it is not safe to eat the fish.
If we go on pouring the rubbish into the sea, it is no longer safe for swimming, as a lot of diseases are present in the water.
If we go on polluting the sea like that , children in the future will not see beautiful blue sea.3.What measures do you think we should take?The government should make laws to protect the sea. We take action like them to protect the sea.
cleaning oilThe people of the Green Peace Organization are struggling with the ship for catching whales.What are they doing?Zhi Hong and Fang Zhou are also talking about protecting the sea . What will they say?We should spread the knowledge about protecting the sea and let people realize the importance of the sea.Listen to the tape and choose the right answer.
1.? What can be done about over fishing?
man-made raising fish
B. In the worst areas they ban fishing for several years
C. control the number of fish people can catch????? 2.??What’s the result of over fishing?
A. there are less fish to catch
B. people can fish too much
C. They can catch more fish than before by better technologyA. there are less fish to catch?3.? What are some government departments doing about sea pollution?
A. punishing people who keep a record of levels of population
B.? thinking of ways to reduce population
C. all departments must be responsible for finding where pollution comes from B.? thinking of ways to reduce populationListen to the tape again and fill in the tape.
1.That’s when people fish _________and the number of fish___________. Some fish may disappear altogether.
2.So there are more fisherman ________________?
Well, they hope to_______________, but there are _________to catch, so they____________.too muchfalls too lowcatching more fishcatch more fishless fishsimply can’t3. It mostly comes from _________waste from_________ and ___________ waste from________.
4.?They also try to help people to _____________________, so there are ___________trying to__________________________.
less peoplemaking a living from fishingindustrialagriculturalfactoriesfarmingget other kinds of jobs2. What is the problem 2?pollutionOver-fishingListen to the interview again and answer the questions1.What is the problem 1?3.What are the reasons for problem 2? too many fisherman in the same place, better technology can catch more fish.4. What are the causes of problem1?chemicals , plastic, rubbish, oil, industry waste, from factories and agricultural waste.5. What are the solutions to problem 1? government departments, look for ways to reduce pollution , keep a record of levels of pollution, finding where it come from, punishing polluters who break the law.6. What are the solutions to problem 2? Control the number of fish that people can catch ,ban fishing completely for a few months, help people to get other kinds of jobs. Read through the example dialogue then make up a new one with your partner.
A: What are you going to do for your sea project?
B: I’m interested in history of sea travel.
A: Oh, really?
B: Yes. I want to know how human beings crossed the sea to land other places in small boat.A: Oh! It is hard to imagine .
B: Mm. They were brave and clever enough to explore unknown land.
A: What do you already know about the subject?
B: I know it wasn’t Columbus but the Viking reached America first.A: Oh, were they?
B: Yes, look at the old map. It is thought that the Viking draw the map that was used by Columbus later.
A: Mm. It is too interesting. What do you need to find out about the subject?B: Who were the first people to reach Australia? How did they arrive?
A: Really? How can you find out more about the subject?
B: I get some information from books and the Internet. I’ll make a cartoon about it.
A: Mm, do you really? That’s sounds wonderful!Homework:
Writing
Practise using the useful words about protecting the sea by making sentences with them:
protect, pollute, pollution, waste, deal with, be responsible for, break the law, punish, keep a record of , control, communicate.THANKS AND BYE!
