In the past oysters were raised in much the same way as dirt farmersraised tomatoes - by transplanting them. First, farmersselected the oyster bed, cleared the bottom of old shells and other debris,then scattered clean shells about. Next, they plantedfertilized oyster eggs, which within two or three weeks hatched intolarvae. The larvae drifted until they attached themselves to the cleanshells on the bottom. There they remained and in time grew into babyoysters called seed or spat. The spat grew larger by drawing in seawater fromwhich they derived microscopic particles of food. Before long,farmers gathered the baby oysters, transplanted them in other waters to speed up their growth, then transplanted them once more intoanother body of water to fatten them up.
Until recently the supply of wild oysters and thosecrudely farmed were more than enough to satisfy peoples needs.But todaythe 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 1900s marinebiologists 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 theproper 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 thatattack and eat baby oysters by the millions. They failed, but they doggedlykept at it. Finally, in the 1940s a significant breakthrough was made.
【考研优美英语作文的背诵034】相关文章:
★ 英语六级作文
最新
2020-09-15
2020-09-15
2020-09-15
2020-08-28
2020-08-28
2020-08-28