Shrimp farming has not able environmental impacts. Once released, the shrimp pond effluent water adds acid and salt to soil, often making eh affected land unsuitable for plants. The released waste can also lead ot eutrophication of nearby marine environments. This means that the nutrient dense shrimp waste can cause plant and algal blooms in marine environments, leading to a lack of oxygen that kills other marine species.
Mangroves are an important part of any coastline and help in maintaining the biodiversity of the area in addition to adding to physical protection by acting as a bio-shield to fragile coastal areas. Attracted by the demand for shrimp in the developed countries, shrimp aquaculture has expanded rapidly, mainly in the subtropical and tropical lowlands of America and Asia. To date, approximately 1-1.5 milliion ha of coastal lowlands have been converted into shrimp ponds, comprising mainly salt flats mangrove areas, marshes and agricultural lands. The impact fo shrimp farming of most concern is the destruction of mangroves and salt marshes for pond construction. Compatibility wit other users, the presence of buffer zones, maintaining an acceptable balance between mangroves and shrimp pond area, improved pond design, reduction of water exchange, and an improved residence time of water, size and capacity to assimilate effluents of the water body, are examples of ways to mitigate the adverse effects. The use of mangroves and halophytes as bio filters of shrimp pond effluents offers an attractive tool for reducing the impact in those regions where mangrove wetlands and appropriate conditions for halophyte plantations exist. Healthy seed supply, good feed with the use of prophylactic agents, good water quality, and lower stocking densities are examples of actions suggested t control disease in shrimp farming.
Key Instructions for Eco-Friendly Shrimp Culture:
- Ensure that the discharge of shrimp farm waste water does not result in long term increase in nutrients of suspended solids in the open waters. The integration of effluent treatment system as a part of the shrimp farm will assist to improve waste water quality and provide long-term strategies for sustainable shrimp farming.
- Do not clear mangroves for shrimp pond construction. Conserve the existing mangroves; deforestation not only affects the mangrove ecosystem but also it reflects negatively on shrimp farming both in India and globally. Presence of mangroves near shrimp ponds cause no harm, rather they are beneficial in many ways. Mangrove trees are the best buffers against winds and waves. Mangroves trees (root, leaf and stem extracts of Rhizophora apiculata) have many medicinal properties. They are found to inhibit human pathogenic organisms.
- Mangroves provide a good environment for the reproduction and growth of other commercially important fishery resources, therefore providing livelihoods for local communities. Avicennia marina and Rhizophora apiculata is the most common mangrove plants found in most of the coastal states which can be grown in varying salinities. The fruiting season of Avicennia marina is from October to November. The ideal season for planting the seedlings is July to November.
- Mangrove seedlings could be easily grown in the nurseries with the locally available seeds/ wildlings. Necessary help for raising seedlings could be secured from the local forest department or organizations like M.S.Swaminathan Research Foundation, Coastal Community Development Agency. Develop mangrove plantations near the existing shrimp farms and nearby mangrove areas through planting of mangrove seedlings.
- Plant mangroves where ever they can be grown on the river and sea side of shrimp ponds in the inter-tidal zone. Planting of mangroves in drain canals and effluent treatment ponds could improve the water quality by absorbing nutrients and other organic pollutants. The mangrove plantations along the bund help in stabilization of banks and prevent soil erosion during floods and reduce sedimentation of ponds during flood.
- Protect the newly planted mangroves with fencing to prevent grazing by animals. Encourage nearby farmers to plant mangroves along their bunds. When contemplating mangrove rehabilitation, special attention must be paid to seed availability, site elevation, spacing of planting, salinity and fresh water runoff, flooding, wave and tidal actions, weed eradiation, nursery techniques monitoring, community participation and total cost of restoration measures.
Mangrove afforestation is being taken up at a large scale in Bangladesh, India and Vietnam principally to provide protection in cyclone- prone areas as well as to generate economic benefits to the poor coastal communities. Restoration of mangroves has received a lot of attention worldwide for several reasons. Firstly, the long ignored ecological and environmental values of mangrove forests have been documented for many mangrove areas. Secondly, there is a subsistence dependence on natural resources from mangrove forests. In addition, large losses of mangroves have occurred throughout the world leading to coastal erosion, decline of fishery resources and other environmental consequences, some of which is in need of urgent attention. Restoration provides an opportunity to improve or enhance the landscape and increase environmental quality. As responsible aquaculture practices become important, protecting mangroves is a core issue.
Source : NaCSA