Look at the four squares [] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? Select a square [] to add the sentence to the passage.
Where would the sentence best fit? Click on a square [] to add the sentence to the passage.
To select a different location，click on a different square.
However, this level of yield did not continue.
我的笔记 编辑笔记
For centuries, commercial fishing off the Canadian Atlantic coast was dominated by cod. The North Atlantic cod fishery operated sustainably for nearly 500 years before suddenly collapsing. From the 1600s through the 1800s, the total Atlantic cod catch ranged from 100,000 tons to 400,000 tons annually. Until 1900, all the cod was salted and dried, with most for export to Europe, where it was a delicacy.After 1900, fishing efficiency improved with larger boats, better nets, and technological enhancements. Freezing replaced the older methods of fish preservation, and by the 1960s, 2 million tons of cod were being harvested annually. By the early 1990s cod populations had dropped dramatically, and the Canadian government closed the collapsed fishery, throwing 35,000 fishers out of work. What went wrong with the management of this fishery?
Two major scientific errors occurred in the management of Atlantic cod stocks during the 1980s and early1990s. First, the estimates of the size of the cod stock were far too high. Cod stocks are estimated by measuring the catch in a series of fishing surveys off the coast. Cod were not randomly spread over the fishing area but were concentrated in high density aggregations; because of this, the estimates of population size were too large. Second, the mortality rate of cod from fishing was grossly underestimated because there are sources of mortality that are not measured by fishery scientists. Young cod that are too small are illegal to sell, and this incidental catch ("bycatch") is usually discarded at sea, causing mortality that is due to fishing but was never measured; because this bycatch did not contribute to the yield of the fishery, it wasn't counted in the harvest. As the abundance of older legal fish was reduced, more and more undersized illegal fish would be caught and discarded. The size of this discarded catch can be enormous, with reports from some fishing trawlers of having to catch 500,000 cod and discard 300,000 undersize fish to get 200,000 legal-sized cod. This increase in mortality rates of young fish would impact directly on how many cod reached the adult age of 6-7 years and could reproduce.
The Atlantic cod collapse has devastated the economy of the Canadian island of Newfoundland and cost Canadian taxpayers at least $4 billion. The recovery of the Atlantic cod will take decades, yet there is continuing political pressure to reopen the fishery. There has been limited evidence of stock recovery during recent years, and cod are only slowly increasing in the absence of a commercial fishery. Fishery scientists estimate that it will take more than a decade to have sufficient population recovery to support a normal fishery for cod. The intervening years look bleak for the fishing industry of Newfoundland, and a fishery that was sustained for 500 years has been destroyed in a few decades.
Because the fishing industry operates in both a social and an ecological framework, it is subject to political conflicts that confront ecological reality. These conflicts are often not resolved, and the fishery suffers. Two forces drive up the fishery's harvest to unsustainable levels. In good years the profits are high and more investments in better boats and better nets are made, and the fishery becomes more efficient. In poor years the government is asked for financial subsidies to maintain employment, and a high harvest rate is maintained when it should be reduced. The net result is to drive the system toward a collapse.
The collapse of the Atlantic cod fishery illustrates "the tragedy of the commons," a term coined by Garrett Hardin in 1968 to describe the overexploitation of resources that are open for anyone to use. Whenever a resource like a marine fishery is held in common by all the people, the best policy for every individual is to overharvest the resource. There can be no reason to stop harvesting at some optimum point because you as an individual can always make more money by overharvesting, and if you do not overharvest, your neighbor will. This overexploitation of common property resources can be averted only by some form of regulations that restrict harvesting, or by converting a common property resource to a private resource through private ownership.
暂无译文