Coastal Habitat Degradation
Mangroves are one of the world's most threatened habitats. Mangrove ecosystems, found in tidal regions throughout the tropics and sub-tropics, not only support local subsistence economies, but offer "ecosystem services" such as recycling of nutrients, coastal protection against floods and hurricanes, and provision of breeding and feeding grounds for fish and crustaceans. Studies in Thailand have estimated the total economic value of intact mangroves as a minimum of $1,000 and possibly as high as $36,000 per hectare. In comparison, shrimp farming was valued at only about $200 per hectare. Yet, one estimate suggests that, of the total global mangrove losses of the past two decades, as much as 38% is attributable to shrimp farm development. In some countries or areas, shrimp farming continues to be the primary threat to mangroves.
Destruction of mangroves has left coastal areas exposed to erosion, flooding and storm damage, altered natural drainage patterns, increased salt intrusion and removed critical habitats for many aquatic and terrestrial species, with serious implications for biodiversity, conservation and food security. Shrimp farm development has also led to the degradation of other important habitats, such as salt marshes, freshwater wetlands and non-mangrove coastal forests. Adjacent coastal and marine ecosystems such as seagrass beds and coral reefs are also threatened. This is due to pollution, in part from shrimp farms, and the loss of mangroves and other wetland habitats, which act as natural filters for terrestrial pollutants and sediments. | ||||
Depletion of wild fish stocks
Mangrove loss has been linked to localised declines in wild fish stocks, resulting from the absence of nursery and feeding grounds afforded by the mangroves for a wide range of juvenile fish. In southeast Asia, mangrove-dependent species account for approximately one third of yearly wild fish landings excluding trash fish. In Thailand an estimated 434g of fish and shrimp are lost from capture fisheries per kg of shrimp farmed in mangrove areas due to habitat conversion alone. In areas of cleared mangrove in Malaysia, local fishermen reported a drop in income of up to 86% within a few years. Degradation of water quality by shrimp farm effluent also has serious implications in terms of depletion of wild fish and shrimp stocks. Bycatch or capture of non-target fish and invertebrate species in places where ponds are still stocked using wild shrimp fry, or where hatcheries still utilise wild adult brood-stock, is hugely wasteful. The by-catch rates associated with juvenile shrimp (fry) collection are thought to be the highest of any fishery. For every fry of the tiger shrimp, Penaeus monodon, collected in India, an estimated 160 fry of fish and other shrimps are lost. At just three collection centres in West Bengal between 62 million and 2.6 billion by-catch fry are estimated to be removed from the ocean in the course of collecting shrimp fry each year. Much of the bycatch consists of juveniles of commercially and ecologically important species, and the very large bycatch can significantly impact biodiversity and capture fisheries production, with serious social repercussions. Even the seemingly reasonable assumption that aquaculture is an efficient way to produce new protein is undermined by the continued use of wild-caught raw fish and fish meal and oil in feeds for growing shrimp. Farming shrimp intensively or semi-intensively can require fish inputs of more than double the weight of the shrimp produced, leading to a net loss of protein and additional pressure being placed on marine reserves for direct human consumption. | ||||
Misuse of chemicals and antibiotics, and coastal pollution
In many commercial shrimp aquaculture systems, farmers stock shrimp at high densities and use high levels of feed, pesticides, antibiotics and other chemicals in order to maximise profits and combat disease. Concerns surrounding such pollutants include their persistence, toxicity, stimulation of resistance, nutrient enrichment, and possible effects on the health of farm workers and consumers. Both chemical and organic wastes from shrimp farms pollute the marine environment. This pollution may be exacerbated by the location of shrimp farms in wetlands due to the loss of the natural filtering services provided by these habitats. Salinisation and depletion of ground and surface water can reduce the productivity of agricultural land surrounding shrimp farms and leave water unusable for drinking or bathing and negatively affect food security and opportunities for income generation for rural communities. | ||||
Spread of DiseasesThis can have a devastating effect on the industry, as well as damaging local subsistence when diseases spread from ponds to wild populations. When the deadly white spot syndrome virus (WSSV) disease hit Ecuador in June 1999, it cut its production by more than 70%. This had national economic implications, as well as socio-economic costs - a total of 150,000 jobs were lost in the shrimp farming industry. | ||||
Introduction of Exotic SpeciesThere are concerns of the impacts of "escapees" in the wild. White shrimp such as Litopenaeus vannamei are the preferred species for consumption for the world's largest shrimp market - the USA. This species, native to the Pacific coast of Mexico and Central and South America as far south as Peru, has been introduced in many other countries such that, for example, it now constitutes 71% of China's total shrimp production. While this species offers various advantages, there are still risks and uncertainties associated with such introductions.
More generally, it is now becoming apparent that many of the introductions and movements of aquatic animals have been responsible for the introduction, establishment and spread of aquatic animal pathogen species (parasites, viruses, bacteria and fungi). Combined with this problem of importing new pathogens is the potential for interbreeding with, and displacement of, native species, with unknown effects on the genetic diversity and ecology of native fauna. If the exotic species were to become established in the wild, there could be a risk of competition with native species. Unfortunately, little is currently known about the effects of cultured shrimp on wild populations and biodiversity but the above risks each have the potential to cause unexpected and far-ranging adverse effects, accompanied by severe socio-economic impacts, particularly as native Penaeid shrimp species support fisheries of commercial importance in several countries, and crustaceans and shrimp are also significant in artisanal coastal fisheries. Read more in EJF's report Farming the Sea, Costing The Earth | ||||
Social impacts and Human Rights Abuses
It is not only the coastal environment that is under threat, but also the lives and livelihoods of countless people who depend upon the services provided. More traditional subsistence economies are undermined as shrimp farms frequently "privatise" public lands and waterways, and restrict local subsistence fishery activities (both through destruction of habitat and preventing access). Hundreds of thousands of coastal people have been displaced, in some cases following land seizures involving use of force. | ||||
Human rights infringements - conflicts over land use have resulted in threats, intimidation of opponents of shrimp farming, and, in at least 11 countries, people have been murdered as a result of such conflict.
Child labour has been reported from a number of countries. Children either collect shrimp fry, spending long hours in water, or work in processing plants for long hours in often squalid condition. Education and health are seriously compromised. Women's lives have been especially impacted as their access to resources and water have diminished. Women have suffered sexual abuse and violence in processing plants and at the hands of armed shrimp farm guards. Read more in EJF's report Smash and Grab |
