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第一段
1 .Listen to part of a lecture in an Environmental Conservation class.
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第二段
1 .Next I want to talk about the collapse of the North American Cod population.
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2 .Let's look at Cape Cod in the northeastern United States.
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3 .the area was named Cape Cod because there was so many Cod fish in the waters just off its shores,
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4 .so many that the first Europeans who fished there in the 17th century reported it was better than in New Finland, Canada.
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5 .At that time, New Finland's Cod fishery was so rich that people said it was possible just to lower a bucket in the water,
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6 .pull it out and it would be full of cod,
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7 .but Cape Cod was even better,
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8 .so the fishing industry there did great until after the 1940s. Uh, there were simply too many fishing vessels,
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9 .sophisticated vessels, competing for fewer and fewer fish.
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10 .In the 1940s there were still about four hundred million pounds of fish caught at Cape Cod every year.
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11 .Just 50 years later though, by the 1990s,
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12 .commercial cod fishing there had become unprofitable.
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13 .The annual catch had gone down about 5% of its 1940s' level.
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第三段
1 .And here's what's so fascinating:
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2 .as more and more fishing vessels with better and better fishing technology were competing for cod,
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3 .this competition was causing changes to the biology of the fish and these changes were making it more and more difficult for the cod population to sustain itself.
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第四段
1 .Changes to the biology of the fish?
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第五段
1 .Well, if a cod fish could reproduce earlier than usual,
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2 .it'd have a better chance of passing on its genes to the next generation before being caught, right?
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3 .And sure enough, biologists noticed that around Cape Cod,
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4 .the cod were beginning to mature at an earlier age than normal.
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第六段
1 .Prior to the population collapse, cod usually took about 8 to 10 years to fully mature, to start to reproduce,
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2 .and they lived around 40 years total.
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3 .So cod had about 30 years of active reproductive life.
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第七段
1 .But now, cod were beginning to reproduce at a younger age, at 3 to 4 years old,
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2 .and they were living shorter lives because they were being caught,
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3 .so they had fewer years within which to reproduce.
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第八段
1 .Additionally, even though some fish in the population were maturing at an earlier age,
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2 .none was actually growing faster.
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3 .No cod has a way of speeding up its rate of growth.
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4 .So the younger reproductive age actually meant that smaller fish were reproducing.
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5 .And when you're a small cod reproducing,
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6 .you produce fewer eggs than a large cod.
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7 .The smaller cods simply don't have the body mass to reproduce as many eggs.
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8 .The overfishing pressure on the cod population was pushing the cod into an evolutionary corner.
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9 .They were having a harder and harder time surviving.
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第九段
1 .But what can be done to prevent other scenarios like this?
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2 .I mean obviously we need a better way to manage environmental resources.
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第十段
1 .Well, what do you guys suggest? Carol?
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第十一段
1 .Hmm, uh, maybe privatize the resource?
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2 .A private owner would want to manage the resource efficiently in a sustainable way.
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第十二段
1 .Ok, but the problem is privatization doesn't necessarily result in better management of an environmental resource.
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2 .Any ideas why it wouldn't?
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第十三段
1 .Well, an individual owner might not properly assess the limits of the resource.
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2 .So they could be just as prone to overexploiting that resource as a group where lots of people have access to it.
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第十四段
1 .Yes. Well, like in the 1970s,
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2 .when it was already clear the North American cod population was declining dramatically,
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3 .the US and Canada declared a 200-mile exclusive economic zone in the waters around Cape Cod.
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4 .By declaring an exclusive economic zone, you see,
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5 .these two countries were trying to extend their territorial waters.
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6 .Basically it was as if they were saying: 'we're the private owners. We own these waters. So we own the rights to the fish in them too.
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7 .Essentially the two countries told fishing vessels, trollers from all other nations, to get out of the cod fishing area.
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第十五段
1 .You'd think that would be good news for the cod because there'd be less fishing.
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2 .However, The US and Canada wanted to expel foreign trollers only in order to increase the number of their own fishing fleets.
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3 .The total number of fishing trawlers actually increased.
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第十六段
1 .Another possible solution, pass laws that regulate use of the resource.
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2 .But for regulation to be effective, penalties for breaking the law have to be large enough to deter violators.
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