反比关系配对题

　　正反比关系配对题，是依据原文内容判断题干同选项之间为正比关系、反比关系或无关系。做这类题目时，除了留意语言重现，还要注意表示数量变化的词汇。

　　Disappearing Fish

　　1 Sea fishing grew rapidly in the decades after the Second World War. Mechanisation increased the fishermen’s catch in traditional grounds and then carried them to distant waters for more. After the world catch had tripled to over 60 million tones in only 20 years, fishing developed more slowly in the 1970s and 1980s, like the rest of the oil-shocked world economy. In 1989, when the sea catch rose above 86 million tones, the growth stopped.

　　2 In 1990 and 1991, the two most recent years for which the Food and Agriculture Organization (FAO) has figures, the world catch began to shrink. It has not been a dramatic fall--only a few percent overall. But experts at the FAO, in common with many fisheries scientists, now believe that the limit to sustainable catches of wild fish was exceeded decades earlier. In more and more waters, too few fish have been left in the sea to maintain levels needed for spawning. Thus fishermen are consuming the very resource that should yield their catch.

　　3 When catches of the most valuable fish in the waters of the northern hemisphere, such as turbot and halibut, started to fail, fleets began instead to chase other species that had been thrown back as "trash" only a generation before--whiting, spiny dogfish and others. They also fished distant waters and found massive catches of a few other low-value species. The FAO notes that it was these short-lived catches-___ of fish such as Alaska Pollack, Peruvian anchoveta and Japanese pilchard____that greatly increased the total world catch in the 1980s.

　　4 But the true, downward trend in fishing worldwide was masked because these catches were measured in tones, not dollars. Moreover, the world’s 3 million or so fishing boats cannot hope for further yields of that kind. There are no more waters and few species that have not been explored. The world’s fishermen say they operate at a loss: $22 billion in 1989, not counting capital expenditure or profit from unreported illegal catches.

　　5 Almost all the 200 fisheries monitored by the FAO are fully exploited. One in three is depleted or heavily overexploited, almost all in the developed countries. Governments have encouraged this excess, by subsidising fishermen, often as a form of regional aid and in response to failing catches. Although fishermen still catch relatively few of the 15,000 existing species of fish, most of the remainder are expensive to catch, taste bad, or both.

　　6 Overfishing is not the only threat to the world’s fisheries, although it is the most severe. Development and pollution are also reducing fish numbers. According to Paul Brouha, director of the American Fisheries Society, between 11 and 15 million salmon once spawned in the Columbia river system. Now there are only 3 million, of which 2.75 million are spawned artificially. So much of the river system has been dammed that only 250,000 salmon can find their way back to old spawning grounds. According to a recent study, three-quarters of the American catch comprises species that depend upon estuaries (often as a habitat for young fish, which can safely feed in the shallow waters).

　　7 But estuaries are themselves vulnerable. Almost a third of the world’s 5.5 billion people live within 60 kilometres of the sea, polluting inshore waters with effluent from industry, and farmland. Lagoons and wetlands are filled to make land; mangrove forests are cut down; fresh water is taken in large quantities upstream, affecting the salinity of estuaries and the growth of young fish.

　　8 For all the damage that they cause, overfishing and pollution rarely lead to extinction (though even this is possible for a few large, slow-growing and valuable species, such as the bluefin tuna). Nor, at least for many years yet, will fish be off the menu for those who have enough money. Indeed, as the price of fish climbs and biotechnology develops, the most valuable fish will increasingly be farmed. Fish farming, or aquaculture, yielded more than 12 million tones in 1990, and is growing by more than 10% a year. Fin-fish make up almost 70% of the total, shellfish a quarter, and shrimp about 6%. But intensive fish farming tends to damage coastlines. And, though the technology is developing rapidly the FAO doubts whether farmed fish will account for more than 12% of world fish consumption by the end of the century.