问题 问答题 论述题

详述养殖鱼类人工繁殖的催产过程。在不同季节怎样安排产卵时间和利用不同水层的水。

答案

参考答案:

一、亲鱼成熟度鉴定目前,主要是依据经验从外观上来鉴别,对雌鱼也可直接挖卵观察。从外观上鉴别可概括为“看、摸、挤”3个字。看就是观察亲鱼腹部是否膨大;摸就是用手触摸亲鱼腹部是否柔软有弹性;挤是用手挤压亲鱼腹部两侧是否有精子或卵子流出。

1.雄亲鱼

成熟的雄鱼,从头向尾方向轻挤腹部即有精液流出,若精液浓稠,呈乳白色,入水后能很快散开,说明亲鱼性成熟好;若精液量少,入水后呈线状不散开,则表明尚未完全成熟,若精液呈淡黄色近似膏状,表明性腺过熟,精巢退化。

2.雌亲鱼

(1)外形观察成熟雌鱼腹部明显膨大,后腹部生殖孔附近饱满、松软且有弹性,生殖孔红润,将鱼腹朝上托出水面,可见腹部两侧卵巢轮廓明显。亲鱼成熟较好。

(2)取卵观察用挖卵器直接从卵巢中取出卵粒进行成熟度鉴别比外形观察更可靠,但可能造成卵巢损伤。若卵粒大小整齐,饱满有光泽,全部或大部分核偏位,表明亲鱼性腺发育成熟,可以马上用于催产;如果卵粒小,大小不均匀,卵粒不饱满,卵核尚未偏位,卵粒相互集结成块,不易脱落,表明卵巢尚未发育成熟,需要进一步强化培育;如果卵粒扁塌,无光泽,卵膜发皱,则表明亲鱼性腺已开始退化,不适宜催产。

二、催产激素

目前用于鱼类繁殖的催产剂主要有绒毛膜促性腺激素(HCG)。鱼类脑垂体(PG)、促黄体素释放激素类似物(LRH-A.等。

三、催产方法

(一)催产季节鱼类人工繁殖生产实际中,应根据以下方面选择最适宜的催产时期。

1.鱼的种类

2.气候

3.性腺发育成熟度

(二)亲鱼捕捞与配组

(三)催产剂注射

1.注射剂量

2.注射液配制

3.注射方法催产剂注射包括体腔注射法和肌肉注射法。

4.注射次数注射催产剂常用一次注射、二次注射两种方法,极少数采用三次注射。一次注射就是将催产药物一次性注人亲鱼体内,二次注射就是将催产药物分两次注入鱼体内。采用二次注射时,一般第一针注射药量偏低,占总预定药量的10%~20%,第二次将剩余药量全部注射人亲鱼体内。5效应时间

四、产卵设施的准备

1.产卵池:使用前要进行彻底的消毒处理。

2.洞穴式人工鱼巢:供喜欢在洞穴中进行配对交配、产卵受精,等鱼类作为鱼巢

3.植物式人工鱼巢:供产黏性卵鱼类作为鱼巢,受精卵附着孵化。

4.其他:担架(鱼夹)、脸盆、毛巾、羽毛、注射器、天平、生理盐水等。

填空题
单项选择题

Americans are often contrasted with the rest of the world in terms of material possessions. We are accused of being materialistic, gadget crazy. And, as a matter of fact, we have developed material things for some very interesting reasons. Lacking a fixed class system and having all extremely mobile population, Americans have become highly sensitive to how others make use of material possessions. We use everything from clothes to houses as a highly evolved and complex means of ascertaining each other’s status. Ours is a rapidly shifting system in which both styles and people move up or down. For example:

The Cadillac (卡迪拉克) ad men feel that not only is it natural but quite insightful of them to show a picture of a Cadillac and a well-turned out gentleman in his early fifties opening the door. The caption (标题) underneath reads, "You already know a great deal about this man. "

Following this same pattern, the head of a big union spends an excess of $100, 000 furnishing his office so that the president of United States Steel cannot look down on him. Good materials, large space, and the proper surroundings signify that the people who occupy the premises (建筑物及其周围所属土地) are solid citizens, that they are dependable and successful.

The French, English, and the Germans have entirely different ways of using their material possessions. What stands for the height of dependability and respectability with the English would be old-fashioned and backward to us. The Japanese take pride in often inexpensive but tasteful arrangements that are used to produce the proper emotional setting.

Middle East businessmen look for something else-family, connections, friendship. They do not use the furnishings of their office as part of their status system; nor do they expect to impress a client by these means or to fool a banker into lending more money than he should. They like good things, too, but feel that they, as persons, should be known and not judged solely by what the public sees.

One of the most common criticisms of American relations abroad, both commercial and governmental, is that we usually think in terms of material things. "Money talks," says the American, who goes on talking the language of money abroad, in the belief that money talks the same language all over the world. A common practice in the United States is to try to buy loyalty with high salaries. In foreign countries, this maneuver almost never works, for money and material possessions stand for something different there from they do in America.

The American who says "Money talks" believes that ().

A. money tells more about a person than anything else does

B. money stands for the same thing all over the world

C. money cannot be used everywhere to do whatever a person wants

D. money cannot buy friendship and loyalty