问题 问答题 简答题

论述气泡病发生的病因、症状以及防治措施?

答案

参考答案:

1)病因:第一、甲烷和硫化氢形成的小气泡。第二、水中气体过饱和(氧和氮)

2)症状:病鱼肠内、体表、鳃或血管内含有气泡,发病鱼苗浮于水面,失去平衡,随着体力的耗尽而死亡。

3)防治措施:

1、避免池中腐殖质过多。

2、防止浮游生物过量繁殖。

3、发现气泡病,每667m2水面用4~6kg食盐水全池泼洒或直接冲入新水。4、鱼苗运输时不要进行急剧送气。

阅读理解

The incident took place on Sunday,the 25th of June. On that particular day,a south wind had been gusting(劲吹) on and off all morning. It was not strong enough to cause us any concern,so we carried on our daily work, not suspecting what was about to happen.

The storm gave us very little warning. Black clouds loomed over the distant horizon(地平线) so suddenly that we were taken by surprise. Even then,we were not really worried,as the clouds seemed to be moving over our house and towards the distant mountains. Then,just as the clouds had moved inland,the wind suddenly swung around in a full circle and we were facing a major storm.

Instantly,we were busily preparing for the worst. The whole family had experienced such a storm before and everyone remembered the damage it had caused to stock and crops. There was very little we could do about the crops. But we needed to protect the animals in case the river flooded again. My older brother called his sheep-dog and began driving our small flock of sheep to higher ground above the river. If the river flooded,they should be safe there.

In the meantime,my father was mending a shed roof that had partly fallen down after many years of fine service. If the tin flew off,it could damage the house. My younger brother began hurriedly carrying firewood under the shelter. My job was to help Mum board up the windows. If the storm developed into a cyclone(旋风),the boards would protect the glass.

The storm raged for four hours,pouring more rain on us than we had seen in the last five years. As expected,the river broke its banks and came slowly up towards the house and the stock..

Then,just as we were beginning to lose hope,the storm stopped as suddenly as it had begun. The animals were safe,and the roof was still nailed on. “All’s well that ends well ,”said my mother.

56.When the black clouds appeared suddenly in the distance,           .

A. the family were surprised    B. they were extremely worried

C. they were preparing for the worst    D. they faced the storm bravely

57.“There was very little we could do about the crops” indicates that           .

A. little damage would be done to the crops          B. they had everything ready for the crops

C. they felt unable to protect the crops                 D. the crops should be safe enough there

58. The underlined word “ stock” in the third paragraph refers to          .

A. money owned by the family                     B. goods for sale

C. supplies for family use                            D. farm animals    .

59.It can be inferred from what the mother said that          ·

A. they had no damage at all                               B. everything went beyond their expectation

C. everything was under control                   D. the family could have suffered a greater loss

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