That matters because theory suggests that the maximum sustainable yield that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels.

　　①Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account.

　　②They believe the data support an idea current among marine biologists, that of the “shifting baseline.”

　　③The notion is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past.

　　④That matters because theory suggests that the maximum sustainable yield that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels.

　　⑤Most fisheries are well below that, which is a bad way to do business.

　　参考译文

　　①(观点：总)迈尔斯博士和沃尔姆博士认为他们的工作将提供一个准确的捕捞数量基线，它是未来渔业管理层必须要考虑的事情。

　　②(具体：分1)他们认为这些数据支持了现在海洋生物学家的一种观点，即“变化中的基线”。

　　③(并列：分2)这种观点认为人们还没发觉海洋中的巨大变化，因为他们只顾了过去相当短的一段时期的情况。

　　④(并列：分3)而这很重要，因为理论认为当目标物种的生物量达到原始基数的 50%左右时，从渔场中能够获得最 大的可持续产量。

　　⑤(并列：分4)大部分渔场都远没达到这个水平，这对于渔业而言是很不利的。