World Aquaculture Magazine - March 2021

40 MARCH 2021 • WORLD AQUACULTURE • WWW.WA S .ORG which provides more than 70 percent of their annual household income. (The average annual household income in Bangladesh is US$ 2162.) Trend in Shrimp Farming Area and Productivity Shrimp productivity was greatest in 2000 and since then has continued to decline until 2010 and then slightly but consistently increased (Fig. 1). The relatively good productivity and market prices in 2000 likely inspired more farmers to adopt shrimp farming, which was reflected by the increased farming area, with the greatest level in 2005 (Fig. 1). However, the farming area has consistently declined since 2005, probably because of the high-risk nature of extensive shrimp farming. Comparative Progress In 1998, Bangladesh produced 66,000 t of shrimp. In the same year India pro- duced 81,000 t and Vietnam produced 116,000 t (Neiland et al. 2001). In 2014, produc- tion in Bangladesh remained almost the same, 68,217 t (DOF 2015). For comparison, in the same year, India pro- duced 385,700 t and Vietnam 492,200 t. Progress in India and Vietnamwas due to the shift in farming to Pacific white shrimp Litopenaeus vannamei , which is now responsible for the majority of their production, government invest- ment in developing farming infrastructure and policies to force the industry to extend their support to smallholder farmers. In addition, in Vietnam, integration of extensive shrimp farms with mangrove forestry, switching to an organic farming approach and certification Farmers carrying boxes of PLs bought from the local market to their ponds (Photo: WorldFish). Traps placed in a pond for regular shrimp harvests without dewatering or much labor (Photo: WorldFish). FIGURE 1. Trend of changing shrimp farming area and productivity from 2000 to 2019 (DOF 2000, 2005, 2010, 2015 and 2019). TABLE 6. Small interventions that can make a big difference in the extensive shrimp farming. Ty p e o f Y i e l d Y i e l d w i t h I n c r e a s e d Gr o s s ma r g i n Gr o s s ma r g i n I n c r e a s e d i n t e r v en t i on c on t r o l i n t e r v en t i on Pr odu c t i v i t y c on t r o l i n t e r v en t i on g r o s s ma r g i n (kg /ha) (kg /ha) (%) (US$) (US$) (%) Increase water depth 20 cm 243 338 39 753 1537 104 Add supplementary feed 1% of shrimp body weight 243 660 172 753 1773 136 Increased depth + supplementary feed 243 811 234 753 2154 186 Supplementary feed (1% of BW) + 2 short cycles + 20 cm increased depth 243 857 253 753 2230 196