Mariculture is culture of marine organisms for commercial purposes. Mariculture may carried out in the open ocean, bays and also in tanks, ponds and raceways filled with seawater. In many coastal countries marine fish, prawns, oysters and seaweed are grown in seawater ponds. Apart from food production, mariculture is done to produce fish meal, fish feed, pearls etc.
Mariculture in open oceans
Aquaculture may be done in the open oceans in floating cages, pens and rafts. Research and commercial mariculture facilities in open oceans are under development and operation in Australia, Chile, China, France, Ireland, Italy, Japan, Mexico, and Norway.
Mariculture in ponds
In these ponds seawater is used for growing fish and prawns. Quality of the seawater is maintained by pumping in fresh seawater or by tidal flow. Marine fish or prawn stocklings are grown with supplementary feeding. This is necessarily a closed culture system and all the optimal environmental parameters have to be maintained as in the freshwater aquaculture.
Environmental effects of open sea culture
There are many controversies about open ocean mariculture. The fish kept in pens and cages have to be fed with high quality formulated feed to achieve faster growth rate. Excess feed and fecal matter of the fish may settle on the seafloor and decay, causing pollution, habitat modification and environmental degradation. Resident organisms may move away from the location. Many non-resident organisms may move in to feed on feed waste and detritus available. This may slowly cause Long-term changes in the abundance and demography of marine organisms of the area creating ecological imbalances.
Another serious problem is about the escapees from the pens and cages. The stocked fish seeds are usually hatchery produced and are very likely to have common genetic lineage. If there is some genetic defect in them and if they escape from the pens or cages there is a great danger of their breeding with the wild population and the spread of the defects to the future wild populations. The defect may cause complete loss of the wild populations.
The parasites and diseases in the cultured fish may pass on to the wild population. The cultured fish may be immune to some disease and when this gets passed on the wild populations during mariculture practices, the results may devastating. Very cautious and well researched actions should be taken for mariculture as there may not be time to correct mistakes and whole marine fisheries may get devastated.
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