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Blue Revolution - An introduction
Blue Revolution - Aquaculture
Blue Revolution - The Environmental Effects
Case Study - Shrimp Farming
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Blue Revolution - The Environmental Effects
The most serious impact of the blue revolution aquaculture is that, rather than increasing global catches, it may very well lead to lower total productivity of our seas.
The intensive, high-density cultivation of fish and shellfish has environmental effects similar to those of intensive livestock or poultry. First and most evident is the accumulation of organic matter, both in the form of unconsumed feed and faeces. When aqua-cultural activities are conducted directly in the marine or brackish environment, this accumulation may well lead to a process of eutrophication, with associated depletion of oxygen near the sea-bottom or throughout the water column and a proliferation of unicellular algae, some of which may be toxic. Compounding these problems is the pollution by pesticides and antibiotics, used intensively when animals are raised in such high densities. The result is a serious loss of local biodiversity. This has particularly occurred in sheltered waters, such as with salmon in Norwegian and Chilean fjords, with the raising of oysters and mussels in lagoons and estuaries, and with the raising of shrimp in ponds.
The loss of mangrove swamps, usually caused by shrimp farming. The loss of mangrove swamps indeed will cause hundreds of species to lose their homes and will result in many large environmental impacts.
The impacts of wetland loss are an exposure of coastal areas to erosion, flooding, increased storm damage, altered natural drainage patterns, increased salt intrusion, and removed critical habitats for aquatic and terrestrial species.
The intensity of aquaculture ponds for shrimp or other species often leads to abandonment of the land after 5-10 years. The local community then suffers the loss of the land’s economic value and the majority of their coastal ecosystem services – losses that easily exceed the benefits attributable to shrimp farming. For example, one study found that total economic value of an intact mangrove in Thailand exceeds that of shrimp farming by 70%.
The practice of feeding typically low-trophic level herbivore fish, fish meal and fish oil; thus increasing the trophic level of farmed fish. Currently, fish inputs can account for more than 40% of total fish feed inputs. The result is an increase in fish meal produced annually for aquaculture from less than 10% in 1980 to over 40% today. Thus, wild fisheries such as anchovies, sardines, herring, and menhaden continue to be exploited in order to sustain the growth of aquaculture.
The loss of wild seed stock. Many aquaculture operations do not reproduce their own stock; they must harvest juvenile fish, commonly referred to as seedstock, in order to maintain their farms from year to year. Some argue that the fish grow larger and faster in the farm environment (especially if they are fed a large percentage of fish-feed), yet that does not counter the problem of the loss of juveniles within the wild food web.
The introduction of exotics into the environment is a huge impact for both terrestrial and ocean habitats. A prime example of the introduction of exotic species due to aquaculture is Atlantic salmon in the Pacific Ocean. Atlantic salmon has been documented in over 80 rivers in British Columbia alone, and currently, escaped farm salmon dominate the number of wild Atlantic salmon in many European rivers. By introducing exotic species to environments around the world, ecosystems and habitats have been and will continue to be altered and degraded. In fact, the United Nations has declared that the introduction of exotic - or alien - species is the greatest threat to global biodiversity after habitat loss.
Outbreaks of pathogens are also a major risk factor in commercial aquaculture with millions of dollars lost annually. Pathogens can not only wipe out a cultured fishery but they also can infect nearby wild species, which can result in a collapse of these wild fisheries. The best way to combat these two impacts would be to establish pen/cage structure regulations and to reduce the amount of pens/cages in open water. In some areas around the world, including Scottish Salmon farming, farms are installing double layered nets to combat this problem.
Overview of the environmental impacts of Aquaculture, which are magnified by the introduction of Blue Revolution:
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