提取牡蠣(Raising Oysters)
in the oysters were raised in much the same way as dirt farmers raised tomatoes- by transplanting them. first, farmers selected the oyster bed, cleared the bottom of old shells and other debris, then scattered clean shells about. next, they "planted" fertilized oyster eggs, which within two or three weeks hatched into larvae.
the larvae drifted until they attached themselves to the clean shells on the bottom. there they remained and in time grew into baby oysters called seed or spat. the spat grew larger by drawing in seawater from which they derived microscopic particles of food. before long, farmers gathered the baby oysters, transplanted them once more into another body of water to fatten them up.
until recently the supply of wild oysters and those crudely farmed were more than enough to satisfy people's needs. but today the delectable seafood is no longer available in abundance. the problem has become so serious that some oyster beds have vanished entirely.
fortunately, as far back as the early 1900's marine biologists realized that if new measures were not taken, oysters would become extinct or at best a luxury food. so they set up well-equipped hatcheries and went to work. but they did not have the proper equipment or the skill to handle the eggs. they did not know when, what, and how to feed the larvae.
and they knew little about the predators that attack and eat baby oysters by the millions. they failed, but they doggedly kept at it. finally, in the 1940's a significant breakthrough was made.
the marine biologists discovered that by raising the temperature of the water, they could induce oysters to spawn not only in the summer but also in the fall, winter, and spring. later they developed a technique for feeding the larvae and rearing them to spat.
going still further, they succeeded in breeding new strains that were resistant to diseases, grew faster and larger, and flourished in water of different salinities and temperatures. in addition, the cultivated oysters tasted better!
-
四級作文:工作還是讀研
在日常的學習、工作、生活中,大家都不可避免地要接觸到作文吧,藉助作文人們可以反映客觀事物、表達思想感情、傳遞知識資訊。你知道作文怎樣寫才規範嗎?下面是小編收集整理的`四級作文:工作還是讀研,僅供參考,歡迎大家閱讀。Forundergraduatescollegestudents,decidi...
-
難忘的父親節關於父親節的英語作文帶翻譯
在學習、工作或生活中,大家對作文都不陌生吧,藉助作文可以宣泄心中的情感,調節自己的心情。爲了讓您在寫作文時更加簡單方便,以下是小編整理的難忘的父親節關於父親節的英語作文帶翻譯,僅供參考,歡迎大家閱讀。父親節快到了,美術老師佈置了一項作業——爲父親製作一張...
-
關於過年英語作文300字三篇
在日復一日的學習、工作或生活中,大家最不陌生的'就是作文了吧,作文是人們把記憶中所存儲的有關知識、經驗和思想用書面形式表達出來的記敘方式。相信寫作文是一個讓許多人都頭痛的問題,以下是小編爲大家收集的過年英語作文300字3篇,歡迎閱讀,希望大家能夠喜歡。過...
-
一封信英語作文10篇
在平凡的學習、工作、生活中,大家都接觸過書信吧,書信是一種應用文體,是人們普遍使用的一種交際工具。相信寫信是一個讓許多人都頭痛的問題,下面是小編精心整理的一封信英語作文,希望能夠幫助到大家。一封信英語作文1尊敬的英語老師:您好!我的名字叫:xxx,是您的新學生。...