Don't tell that to your local sushi chef. Over the past three decades, the fish export trade has grown fourfold, to 30 million tons, and its value has increased ninefold, to $ 71 Billion. The dietary attractiveness of seafood has stoked demand. About 90% of the ocean's big predators like cod and tuna--have been fished out of existence. Increasingly, fish and shrimp farms are filling the shortfall. Though touted as a solution to overfishing, many of them have--along with rampant coastal development, climate change and pollution devastated the reefs, mangroves and seagrass beds where many commercially valuable fish hatch.
Steven Murawski, chief scientist at the U. S. National Marine Fisheries Service, finds Worm's headlining prediction far too pessimistic, Industry experts are even more skeptical "There's now a global effort to reduce or eliminate fishing practices that aren't sustainable," says industry analyst Howard Johnson. "With that increased awareness, these projections just aren't realistic."
Perhaps. Still, the destructive fishing practices that have decimated tuna and cod have not declined worldwide, as Johnson suggests. Up to half the marine life caught by fishers is discarded, often dead, as bycatch, and vibrant coral forests are still being stripped bare by dragnets. Worm argues that fisheries based on ecosystems stripped of their biological diversity are especially prone to collapse. At least 29% of fished species have already collapsed, according to the study, and the trend is accelerating.
what's a fish eater to do? "Vote with your wallet," says Michael Sutton, who runs the Monterey Bay Aquarium's Seafood Watch program in California. Since 1999, the aquarium has handed out pocket guides listing sustainably harvested seafood. The Marine Stewardship Council has partnered with corporations to similarly certify wild and farm-raised seafood. Some 370 products in more than two dozen countries bear the British group's "Fish Forever" label of approval. Wal-Mart and Red Lobster, among others, have made commitments to sell sustainably harvested seafood.
But that's just a spit in the ocean unless consumers in Japan, India, China and Europe join the chorus for change. "If everyone in the U. S. started eating sustainable seafood," says Worldwatch Institute senior researcher Brian Halweil, "it would be wonderful, but it wouldn't address the global issues. We're at the very beginning of this."
It can be inferred from the first paragraph that ______.
A.fishermen are afraid of pirates and storms most.
B.people should take measures to secure fish supply.
C.about 50 years later, we won't be able to eat fish.
D.Worm expects global catch data to continue surging.
第2题
设信道带宽为4kHz,信噪比为,30dB,按照香农定理,信道最大数据速率约等于()。
A.10Kb/s B.20Kb/s C.30Kb/s D.40Kb/s
第3题
设信道带宽为4kHz,信噪比为30dB,按照香农定理,信道的最大数据传输速率约等于
A.10 Kb/s
B.20 Kb/s
C.30 Kb/s
D.40 Kb/s
第4题
● 设信道带宽为4kHz,信噪比为30dB,按照香农定理,信道的最大数据速率约等于(16) 。
(16)
A. 10Kb/s
B. 20Kb/s
C. 30Kb/s
D. 40Kb/s
第6题
● 设信道带宽为4kHz,信噪比为30dB,按照香农定理,信道的最大数据速率约等于(16) 。
(16)
A. 10Kb/s
B. 20Kb/s
C. 30Kb/s
D. 40Kb/s
第8题
根据香农定理,带宽为4000Hz、信噪比为30dB的信道容量是()。
A.20Kbps
B.21.7Kbps
C.40Kbps
D.42.7Kbvs
第9题
设信道带宽为4000Hz,信噪比为30dB,按照香农定理,信道容量为 (15) 。
A.4Kb/s
B.16Kb/s
C.40Kb/s
D.120Kb/s
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