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  3. Don’t Waste Our Oceans [A]For too long, marine life has been largely open for the taking by anyone possessing the means to explo

Don’t Waste Our Oceans [A]For too long, marine life has been largely open for the taking by anyone possessing the means to explo

admin2015-02-12  59
问题                     Don’t Waste Our Oceans
[A]For too long, marine life has been largely open for the taking by anyone possessing the means to exploit it. Rapid advances in technology have meant that the ability, reach and power of vessels and equipment used to exploit marine life now far outweigh nature’s ability to maintain it. If left unchecked, this will have far reaching consequences for the marine environment and for people who depend on it. Ocean life comes in an incredible array of shapes and sizes — from microscopic plankton to the largest of the great whales. Yet many species have been, or are being, driven towards extinction through devastating human impacts. The key threats facing our ocean creatures include:
Industrial Fishing
[B]Many marine ecologists think that the biggest single threat to marine ecosystems today is overfishing. Our appetite for fish is exceeding the oceans’ ecological limits with devastating impacts on marine ecosystems. Scientists are warning that overfishing results in profound changes in our oceans, perhaps changing them forever. Not to mention our dinner plates, which in future may only feature fish and chips as a rare and expensive delicacy.
The fish don’t stand a chance
[C]More often than not, the fishing industry is given access to fish stocks before the impact of their fishing can be assessed, and regulation of the fishing industry is, in any case, woefully inadequate. The reality of modern fishing is that the industry is dominated by fishing vessels that far out-match nature’s ability to replenish fish. Giant ships using state-of-the-art fish-finding sonar can pinpoint schools offish quickly and accurately. The ships are fitted out like giant floating factories—containing fish processing and packing plants, huge freezing systems, and powerful engines to drag enormous fishing gear through the ocean. Put simply: the fish don’t stand a chance.
Ocean life health check
[D]Population of top predators, a key indicator of ecosystem health, are disappearing at a frightening rate, and 90 percent of the large fish that many of us love to eat, such as tuna, swordfish, marlin, cod, halibut, skate, and flounder — have been fished out since large-scale industrial fishing began in the 1950s. The depletion of these top predator species can cause a shift in entire oceans ecosystems where commercially valuable fish are replaced by smaller, planktonfeeding fish. This century may even see bumper crops of jellyfish replacing the fish consumed by humans. These changes endanger the structure and functioning of marine ecosystems, and hence threaten the livelihoods of those dependent on the oceans, both now and in the future.
Fisheries collapse
[E]The over-exploitation and mismanagement of fisheries has already led to some spectacular fisheries collapses. The cod fishery off Newfoundland, Canada collapsed in 1992, leading to the loss of some 40,000 jobs in the industry. The cod stocks in the North Sea and Baltic Sea are now heading the same way and are close to complete collapse. Instead of trying to find a long-term solution to these problems, the fishing industry’s eyes are turning towards the Pacific — but this is not the answer. Politicians continue to ignore the advice of scientists about how these fisheries should be managed and the need to fish these threatened species in a sustainable way.
Bycatch
[F]Many fisheries catch fish other than the ones that they target and in many cases these are simply thrown dead or dying back into the sea. In some trawl fisheries for shrimp, the discard may be 90 percent of the catch. Other fisheries kill seabirds, turtles and dolphins, sometimes in huge numbers.
[G]Estimates vary as to how serious a problem bycatch is. Latest reports suggest that around eight percent of the total global catch is discarded, but previous estimates indicated that around a quarter of which might be thrown overboard. Simply no one knows how much of a problem this really is. The incidental capture, or bycatch, of mammals, seabirds, turtles, sharks and numerous other species is recognized to be a major problem in many parts of the world. This figure includes non-target species as well as targeted fish species that cannot be landed because they are, for instance, undersized. In short, anywhere between 6.8 million and 27 million tones offish could be discarded each year, reflecting the huge uncertainties in the data on this important issue.
[H]The scale of this mortality is such that bycatch in some fisheries may affect the structure and function of marine systems at the population, community and ecosystem levels. Bycatch is widely recognized as one of the most serious environmental impacts of modern commercial fisheries.
The victims
[I]Different types of fishing practices result in different animal species being killed as bycatch: nets kill dolphins, porpoises and whales, longline fishing kills birds, and bottom trawling devastates marine ecosystems.
[J]It has been estimated that a staggering 100 million sharks and rays are caught and discarded each year. Tuna fisheries, which in the past had high dolphin bycatch levels, are still responsible for the death of many sharks. An estimated 300,000 cetaceans(whales, dolphins and porpoises)also die as bycatch each year, because they are unable to escape when caught in nets. Birds dive for the bait planted on long fishing lines, swallow it(hook included)and are pulled underwater and drowned. Around 100,000 albatrosses are killed by longline fisheries every year and because of this, many species are facing extinction.
[K]Bottom trawling is a destructive way of "strip-mining" the ocean floor, harvesting the species that live there. As well as the target fish species, this also results in bycatch of commercially unattractive animals like starfish and sponges. A single pass of a trawl removes up to 20 percent of the seafloor fauna and flora. The fisheries with the highest levels of bycatch are shrimp fisheries: over 80 percent of a catch may consist of marine species other than the shrimp being targeted.
Technology
[L]Many technical fixes exist to reduce bycatch. Turtle exclusion devices are used in some shrimp fisheries to avoid killing turtle species. In the case of longline fisheries, the process of setting the hooks can be changed and bird-scaring devices employed which radically cut the numbers of birds killed. To avoid dolphins being caught in nets, other devices can be used. Pingers are small sound-emitting and dolphin-deterring devices that are attached to nets, but they are not always effective. Escape hatches(consisting of a widely spaced metal grid, which forces the cetacean up and out of the net)have also been used.
[M]Although these devices may have a role to play, they cannot address the whole problem. Such devices need continual monitoring to check how well they work and assess any potential negative effects they may have. Realistically they will probably only be used in areas with well-developed fishery management and enforcement agencies.
[N]On a global level, probably the only effective way to address the problems of bycatch is to control fishing effort. This will be best achieved through the creation of marine reserves. Nonetheless, in the case of highly mobile species such as seabirds and cetaceans, the only effective way of preventing bycatch is to discontinue the use of particularly damaging fishing methods.
Defending Our Oceans
[O]Fundamental changes need to be made in the way our oceans are managed. This means that we must act to make sure that human activities are sustainable, in other words that they meet human needs of current and future generations without causing harm to the environment. Accordingly, governments must set aside 40 percent of our oceans as marine reserves. Marine reserves can be defined as areas of the ocean in which the exploitation of all living resources is prevented, together with the exploitation of non-living resources such as sand and gravel and other minerals.
Shrimp fisheries has the highest levels of bycatch.
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