28 MARCH 2018 • WORLD AQUACULTURE • WWW.WAS.ORG from three major events. Capture of shrimp from the ocean steadily increased until about 2003, after which it fluctuated between 3.2 and 3.6 million t/yr with no clear trend of an increase or decrease (Fig. 1). This has resulted in a growing demand for farmed shrimp. Nutritionally-complete and reasonably-priced shrimp feeds were developed that allowed farmers to produce higher yields than possible in fertilized ponds (Lovell 1988). Relatively inexpensive, mechanical aerators were designed and manufactured that allowed greater shrimp stocking and feeding rates without causing dissolved oxygen depletion (Boyd and Watten 1989). The development in Hawaii of high-health Litopenaeus vannamei broodstock, a penaeid shrimp species native to the western hemisphere, was also a major milestone (Wyban 2009). These broodstock were introduced into Thailand in 2001, and in 2002, Thailand produced 60,000 t of L. vannamei. The culture of this species quickly spread from Thailand to other Asian countries (Briggs et al. 2005, Chavanich et al. 2016). Since 2003, global production of farmed shrimp has increased from slightly over 2 million t to nearly 5 million t in 2015, and the increase in production has resulted mainly from greater L. vannamei production (Fig. 2). A number of penaeid species have been cultured since the 1950s and 1960s. The main species reported in FAO statistics were L. vannamei, Metapenaeus ensis, M. monoceros, Penaeus chinensis, P. indicus, P. japonicus, P. merguiensis, P. monodon, P. penicillatus, P. schmitti, and P. stylirostris. By the late 1990s, P. monodon represented over 50 percent of shrimp production but was overtaken by L. vannamei in 2003. Since then, L. vannamei has accounted for over 50 percent of annual production with its dominance increasing each year (Fig. 2). Production of P. monodon has typically been above 600,000 t/yr since 2000 but, with no clear trend of increase (Fig. 2). In 2015, L. vannamei accounted for 79.6 percent of farmed shrimp, while P. monodon contributed 14.6 percent — these two species represented 94.2 percent of global production (Table 1). The introduction of L. vannamei has changed the features of shrimp aquaculture in Asian countries other than Myanmar and Bangladesh. The effects of this introduction on the characteristics Aquaculture has been practiced for at least two millennia (Stickney 2000) but only recently did it become a significant sector of world seafood production. Most shrimp and fish aquaculture is conducted in ponds and construction of ponds involves land use conversion. Ponds require a water source and often are constructed on the flat land of floodplains near streams or estuaries. Ponds also may be sited in lower areas of watersheds and filled by storm runoff (Yoo and Boyd 1994). Land for ponds usually was formerly in agriculture or was undeveloped natural land that frequently included wetlands (Boyd and McNevin 2015). Penaeid shrimp farming usually is conducted in coastal ponds where saline water can be obtained from nearby estuarine systems or the sea. Shrimp ponds may be sited within the intertidal zone and filled and drained by tidal action or they may be located above mean sea level and saline water pumped into them. Shrimp farming has resulted in salinization of agricultural land (Primavera 2006, Cao et al. 2007, Rahman et al. 2013), conversion of valuable agricultural land to ponds (Lan 2013, Rahman et al. 2013) and clearing of mangrove areas or other coastal wetlands of particularly high ecological value (ADB/NACA 1997). Coastal land conversion to shrimp ponds is a major environmental concern about shrimp farming (Chua 1992, Massaut 1999, Thu and Populus 2007). History and Characteristics of Global Shrimp Aquaculture Shrimp farming has been done for over a century but it did not flourish until the mid-1980s, and around 1,000,000 ha of shrimp ponds were constructed by 1989 (Rosenberry 1991). Verdegem and Bosma (2009) estimated the global area of brackishwater ponds but shrimp ponds were not separated from the total. Examination of their data suggested that there were possibly about 1,800,000 ha of coastal shrimp ponds by 2004. Global shrimp production increased from 620,280 t in 1989 to 2,364,024 t in 2004 — an increase in global pond yield from 620 kg/ha/yr to 1,313 kg/ha/yr. Since 2004, global shrimp production has continued to increase, reaching 4,875,586 t in 2015 (Fig. 1). The great increase in cultured shrimp production resulted Land Use in Shrimp Aquaculture Claude E. Boyd and Aaron A. McNevin FIGURE 1. Global shrimp production (1950-2015). Source: www.fao.org/ faostat/en/. FIGURE 2. Global production of total penaeid shrimp versus production of Litopenaeus vannamei and Penaeus monodon (1990-2015).
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