Fish species are expected to shrink in size by up to 24% because of global warming, say scientists.
The scientists argue that failure to control greenhouse gas emissions will have a greater effect on marine ecosystems than previously thought. Previous research has suggested that changing ocean temperatures would affect both the distribution and the reproductive abilities of many species of fish. This new work suggests that fish size would also be heavily affected.
The researchers built a model to see how fish would react to lower levels of oxygen in the water. As ocean temperatures increase, so do the body temperatures of fish. But, according to lead author, Dr William Cheung, from the University of British Columbia, the lower level of oxygen in the water is key. Warmer waters could decrease ocean oxygen levels and greatly reduce fish body weight. On the other hand, rising temperatures directly increase the metabolic rate of the fish's body function. This leads to an increase in oxygen demand for normal body activities. So the fish will run out of oxygen for growth at a smaller body size.
The research team also used its model to predict fish movements as a result of warming waters. The group believes that most fish populations will move towards the Earth's poles at a rate of up to 35km per decade. So in, say, the North Sea, says Dr Cheung, one would expect to see more smaller-body fish from tropical waters in the future.
Taking these factors into consideration, the research team concludes that fish body size will shrink between 14% and 24%, with the largest decreases in the Indian and Atlantic oceans.
When pared with actual observations of fish sizes, the model seems to underestimate what's actually happening in the seas. The researchers looked at two case studies involving North Atlantic cod and haddock. They found that recorded data on these fish showed greater decreases in body size than the models had predicted.
Dr Alan Baudron, from the University of Aberdeen, UK, believes smaller-sized fish could seriously affect the ability of fish to reproduce. Smaller fish produce fewer and smaller eggs which could affect the reproductive potential of fish stocks, he said.
【小题1】What's the main idea of the passage?A．Global warming makes fish smaller.B．Global warming makes fish decrease in numbers.C．Global warming affects the fish distribution.D．Global warming affects the ability of fish to reproduce.【小题2】What is the key factor making the fish smaller now?A．The rising body temperatures.B．The lower level of oxygen in the water.C．The increasing metabolic rate.D．The normal body activities.【小题3】We can infer that as ocean temperatures increase .A．more big fish will be born in the seaB．fish tend to swim towards the shoreC．fish tend to move towards the warm areasD．fish tend to move towards the colder areas【小题4】What does the underlined word underestimate mean?A．make an exact prediction ofB．make too low an estimate ofC．make too high an estimate ofD．make a careful study ofA
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(答案→)A
解析：文章大意：科学研究表明，由于全球变暖，使得鱼变得越来越小。
【小题1】A主旨大意题。根据大意及文章第一句Fish species are expected to shrink in size by up to 24% because of global warming, say scientists.可以归纳出文章的主旨大意。故A正确。
【小题2】B细节判断题。由第三段But, according to lead author, Dr William Cheung, from the University of British Columbia, the lower level of oxygen in the water is key. Warmer waters could decrease ocean oxygen levels and greatly reduce fish body weight.可得水中的氧气是关键。故B正确。
【小题3】D推理判断题。根据本段文章中第四段The group believes that most fish populations will move towards the Earth's poles at a rate of up to 35km per decade.可以推测鱼趋向于朝更冷的地方移动。故D正确。
【小题4】B词义推测题。根据文章的倒数第二段They found that recorded data on these fish showed greater decreases in body size than the models had predicted.可知underestimate为“低估”之意。故B正确。