Shrimp farming utilizes large concrete ponds or enclosures where juvenile shrimp grow until of harvestable size (Rosenberry 2006a; EJF 2004; Kungvankiv 1984). Typically shrimp ponds are located on an estuary or near coastal waters to provide a source of brackish or saltwater (Cardenal 1997). Three types of shrimp farm designs (extensive, semi-intensive, and intensive) exist. Extensive, or low-density, farms raise natural assemblages of shrimp, crab and fish by enclosing mangroves and intertidal areas in large ponds. Extensive shrimp farms occur predominantly in tropical regions and constitute 59% of farms and have stocking densities of 1-3 shrimp per square meter (Rosenberry 2006a; EJF 2004). Semi-intensive systems, which constitute 29.5% of farms, use small ponds from which natural vegetation is cleared. Semi-intensive shrimp farms have stocking densities of 5-8 shrimp per square meter and typically require stocking of wild shrimp fry (EJF 2004; Kungvankij 1984). Intensive systems constitute 11.5% of farms and use small ponds cleared of natural vegetation. Intensive shrimp farms have stocking densities of over 20 shrimp per square meter (EJF 2004).

Extensive shrimp farming occurs largely in Vietnam, Indonesia and Ecuador. Semi-intensive farming occurs in Honduras, Mexico, Columbia, Ecuador and China, while intensive shrimp farming is common throughout major shrimp farming regions of the world including Thailand, Indonesia, and Taiwan (Rosenberry 2006a).

The world's production of farm-raised shrimp is dominated by developing countries located in tropical regions. Farm-raised shrimp production has increased dramatically in recent decades (EJF 2004; Paez-Osuna 2001; Naylor et al. 1998; Cardenal 1997). From the early 1980s to the mid-1990s, shrimp aquaculture production has grown by a factor of 7, and today farms supply more than one quarter of the shrimp consumed worldwide (Huitric et al. 2002; Naylor et al. 1998; Cardenal 1997). Along with increased shrimp production, the intensity and density of shrimp farms has exploded along tropical coastlines (Cardenal 1997).

Lure by profits, many private investors and governments promote the growth of intensive shrimp farms throughout the developing world (EJF 2004). Large, intensive shrimp farms remove large tracts of mangroves and wetlands, and discharge greater quantities of effluent than smaller, low-density extensive systems (Rosenberry 2006a). Dramatic increases in intensive shrimp systems throughout exporting nations in the last few decades continue to increase environmental impacts (EJF 2004; Naylor et al. 1998).

The dramatic increase in shrimp aquaculture has been widely supported by national governments, private investors and international development and aid agencies motivated by increased profits, foreign exchange and employment (EJF 2004; Naylor et al. 1998).

Most shrimp farms use a combination of live feeds, such as microalgae and brine shrimp nauplii, with a prepared feed (Rosenberry 2006a). Extensive, or low density, shrimp farms often do not feed at all, depending upon natural assemblages of prey present in the system to support developing shrimp (Rosenberry 2006a). Semi-intensive and intensive shrimp farms, in contrast, rely on the addition of feed to support growth. Within the major exporting countries of farm-raised shrimp, prepared shrimp feed typically contains between 30-35% fishmeal and 3% fish oil (Rosenberry 2006a; Naylor et al. 1998).

Typically, shrimp feed contains between 30 to 35% of fishmeal (Rosenberry 2006a; Naylor et al. 1998). Shrimp farms in many Asian exporting nations rely largely on natural foods such as molluscs, crustaceans and 'trash fish' caught as bycatch in local fisheries, including wild-caught shrimp fisheries (Rosenberry 2006a). In many tropical shrimp trawl fisheries, bycatch which was formerly discarded is now being utilized (Zeller and Pauly 2005; FAO 2001). Since many tropical shrimp trawl fisheries occur adjacent to low-income, food deficient countries, local governments do not discourage the amount of bycatch being caught, but rather encourage its use once it is caught (FAO 2001). Most of the 1.8 million tones of bycatch produced by the Chinese shrimp trawl fishery, for example, provide feed for the Chinese aquaculture industry (FAO 2001). In Southeast Asia ¨C where exports supply the majority of shrimp to the U.S. - government agencies offer assistance in the move towards the use of bycatch species for the production of traditional food products and aquaculture feeds (FAO 2001). Recent analyses also suggest a trend of increased utilization of bycatch amongst the countries of Central America and the Caribbean. In Belize, Colombia, Costa Rica and Nicaragua, between 20 to 30% of bycatch produced by shrimp trawl fisheries is now being utilized (FAO 2001).

Feed conversion ratios (FCRs) for farmed shrimp are high. Although environmental conditions and the quality of feed can result in varying FCRs, the average FCR for P. monodon according to a recent study is 2.77 (Salama 2005).

The production of farmed shrimp results in numerous biological and chemical wastes, including uneaten feed, waste products, antibiotics, fertilizers, disinfectants and pesticides (EJF 2004; Paez-Osuna 2001). Moreover, the nature of shrimp to slowly nibble food particles causes substantial loss of highly organic feed, which farms frequently discharge directly into the environment (Rosenberry 2006a). Shrimp farm effluents can lower the quality of the surrounding water, overwhelm the environment and create conditions favorable for shrimp pathogens (Rosenberry 2006a).

Shrimp farms typically rely on tidal flow and diesel pumps to continually flush out wastes and introduce freshly oxygenated water to the ponds (Rosenberry 2006a; Cardenal 1997).
Effluent discharge depends largely on the type of farm design (extensive, semi-intensive, or intensive). Extensive (low-density) farms exchange 0-5% of their water each day (Rosenberry 2006a). Semi-intensive farms exchange between 0-25% of their water per day, while intensive (high-density) farms exchange 30% or more of their water per day (Rosenberry 2006a). The high exchange rates associated with intensive shrimp farms frequently cause environmental problems (Rosenberry 2006a; Cardenal 1997).

Given the varying degrees of effluent treatment among the existing farm systems, the large number of exporting nations supplying farmed shrimp to the United States and the difficulties in differentiating between wild-caught and farm-raised shrimp imports (National Marine Fisheries Service trade data does not seperate between wild-caught and farm-raised imports; NMFS 2006), we chose to award a score of 2.00 for this factor

The destruction of mangroves associated with shrimp farming exposes coastal areas to erosion, flooding, storm damage, altered drainage patterns, and loss of critical habitat for a large number of marine and terrestrial species (EJF 2004). Since mangroves and other wetlands act as a natural filter for pollutants and sediments, destructive shrimp farming practices can affect adjacent habitats, such as coral reefs and seagrass beds (EJF 2004). The loss of mangroves has been associated with declines in wild fish and shrimp populations (EJF 2004). Degradation of water quality by shrimp farm effluent has also been linked to declines in wild fish and shrimp populations (EJF 2004).

Shrimp farms frequently exchange biological and chemical wastes including shrimp waste products, uneaten feed, antibiotics, pesticides and other additives with surrounding coastal waters (Rosenberry 2006a; EJF 2004; Quarto 1998). In Asia, intensive shrimp farms typically succeed for only 2 to 5 years, before pollution and disease problems associated with high stocking densities force their closure (Rosenberry 2006a; Quarto 1998).

The escape frequency of farm-raised shrimp is not known. The Giant Tiger Shrimp, Penaeus monodon and the Western White Shrimp, Penaeus vannamei, account for approximately 85% of shrimp production throughout the world (Rosenberry 2006b). Native to the Indian Ocean and the southwestern Pacific Ocean from Japan to Australia, P. monodon represents one third of shrimp production in Asia (Rosenberry 2006b). Although P. monodon are large and fast growing, captive breeding is difficult and hatchery survival is low. Native to the Pacific Coast of Central and South America from Mexico to Peru, the Western White Shrimp, P. vannamei, represents more than 99% of shrimp production in the Western Hemisphere. High survival rates of P. vannamei, in contrast to P. monodon, led shrimp farms throughout Asia to cultivate non-native P. vannamei, which now supply the majority of shrimp production around the world (Rosenberry 2006b).

The effects of non-native farmed shrimp on local populations of fish and shellfish are not well understood (Quarto 1998; Cardenal 1997). Since further research is still needed in this area, we chose to neither add nor subtract for this factor.

Most intensive shrimp farms suffer from high mortality rates due to disease. Referred to as 'boom and bust' cycles, shrimp farm production often peaks and plummets in response to major disease outbreaks. Major shrimp disease outbreaks occurred in the Philippines (1988), Taiwan (1987-8, 1993), Sri Lanka (1989), Thailand (1991, 1996), Ecuador (1989, 1994, 2000), China (1993), Vietnam (1993), Indonesia (1994), Bangladesh (1994, 1996) and India (1995) (Rosenberry 2006a; EJF 2004; Paez-Osuna 2001). Shrimp farms throughout the Western Hemisphere suffer from Whitespot disease, formerly common to the Eastern Hemisphere, while shrimp farms in the Eastern Hemisphere suffer from the Taura virus which arrived from the Western Hemisphere (Rosenberry 2006a). Since its first appearance in 1992 in Ecuador, the Taura virus (also referred to as Taura syndrome) has spread to every shrimp producing country in the Western Hemisphere, with the exception of Venezuela, and threatens many shrimp farms throughout the Eastern Hemisphere (Rosenberry 2006a).

Shrimp farming occurs in over 50 countries, with developing nations in tropical regions supplying 99% of the production (Rosenberry 2006a; EJF 2004). Typically shrimp farms are located on an estuary or near coastal waters which provide a source of brackish or saltwater (Cardenal 1997). Shrimp farm development damages important wetland habitats, including mangroves, salt flats and marshes, mudflats, and freshwater wetlands and degrade surrounding habitat with effluent discharge (EJF 2004; Paez-Osuna 2001; Cardenal 1997).

Recent estimates suggest that shrimp farming development contributes as much as 38% of recent mangrove loss worldwide (EJF 2004; Paez-Osuna 2001). Since mangroves act as natural filters, mangrove loss exposes coastal areas to erosion, flooding and storm damage and removes critical habitat for a large number of marine and terrestrial species (EJF 2004). Increased erosion and siltation that occurs in areas where extensive mangrove clearance occurred can destroy important downstream habitats, such as seagrass beds and coral reefs (Cardenal 1997). Mangroves provide breeding and nursery habitat for a substantial proportion of the earth's fish and shellfish populations. Direct relationships between declining mangroves and declining fish catches have been observed (Cardenal 1997).

In addition to habitat destruction, shrimp farms dispose effluent into the surrounding ecosystem, introducing salt to surrounding soil and water and degrading the quality of coastal waters (Quarto 1998; Naylor et al. 1998). Brackish water leaving intensive shrimp farming operations infultrates from culture ponds into the groundwater, threatening domestic and agricultural water supplies (Paez-Osuna 2001).

In many exporting nations, shrimp farms utilize larval and adult shrimp collected from the wild (EJF 2004; Paez-Osuna 2001; Kungvankij 1984). The collection of wild shrimp larvae, or fry, removes large quantities of non-target fish and invertebrate species. Bycatch rates associated with shrimp fry collection are believed to be the highest of any fishery (EJF 2004). The shrimp aquaculture industry in Bangladesh depends largely on wild seed (ie. larval and juvenile shrimp) collection (FAO 2001; Cardenal 1997). Although seed collectors remove more than 2 billion larvae of Tiger Prawn, Penaeus monodon, annually, this figure represents only 2% of the total catch; the remainder consisting of other Penaeid shrimp, prawns, finfish larvae and zooplankton species (FAO 2001). Wild fry collectors in India, remove an estimated 160 fry of fish and other shrimp species for every 1 fry of P. monodon (EJF 2004).

Shrimp farms utilize a number of deterrents in efforts to scare off migrating birds, which often land on shrimp farms and consume large quantites of shrimp. Detterents including noise cannons, rockets and scarecrow work with minimal success. Since birds are protected in almost all exporting shrimp farming nations, harmful or lethal predator deterrents are not commonly used to deter predation (Rosenberry 2006a).