70 DECEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG vegetables and fruits and rice is the most common form of IAA (17 percent of farms), followed by integration with only vegetables and fruits (16 percent), and integration with only rice (12 percent). The potential for integration of terrestrial foods is related to the type of aquaculture practiced. Giant freshwater prawn is produced in freshwater or low-salinity environments and is thus well-suited to integration with terrestrial foods. Shrimp (mainly black tiger shrimp) is produced in saline water that damages terrestrial food crops, making crop integration more difficult. However, there is significant overlap in the range of salinities in which both crustacean species can thrive, giving rise to a diverse mix of IAA. Most households producing prawn integrate with agriculture (81 percent), whereas IAA is only moderately common for households that produce only fish (35 percent), and comparatively rare for those producing shrimp (15 percent). The diversity of production in our sample varies by farming system and by the combinations of foods produced on each farm. Farms harvested an average of nine aquatic products each, while the 32 percent of households that produced vegetables and fruits harvested 3.5 types each on average. Figure 5 presents the economic productivity per hectare by farming system, disaggregated into aquatic foods, vegetables and fruits, and rice. The most profitable farming systems produce fish, prawn, and shrimp with rice, vegetables, and fruits (4,379 USD/ha), and fish and prawn with rice, vegetables and fruits (3,947 USD/ha). The least economically productive farming systems produce fish integrated with rice (1,249 USD/ha), and fish integrated with rice, vegetables, and fruits (1,335 USD/ha). Figure 6 extends this comparison by presenting the economic productivity per hectare, overlaid with estimates of productivity of energy, protein, calcium, iron, zinc, vitamin A, and vitamin B12, expressed as AEs/ha, by farming system. The figure shows that the nutrient productivity of farming systems is partly disconnected from their economic productivity. IAA systems that combine fish and prawn with vegetables and fruits and rice – one of the most economically productive food combinations – also have the highest productivity of energy, protein, iron, zinc, and vitamin A. However, whereas the economic productivity of farming systems that include shrimp but are not integrated with terrestrial foods is close to the sample average, these systems supply much lower-than-average quantities of almost all nutrients per hectare. These results point to positive associations between the integration of terrestrial foods into aquatic farming systems and nutrient productivity. Further Analysis The relationships outlined above are analyzed with greater precision in a regression analysis presented in the full paper, where we divided the three main food groups into four sub-categories of aquatic food and eight sub-categories of terrestrial food, and regressed economic productivity and nutrient productivity against the quantities of each group of foods produced and numerous control variables. We found a positive and significant relationship between the productivity of three out of four aquatic food groups and economic productivity, with yields of crustaceans having the largest positive correlation with economic productivity, followed by yields of carp species. Yields of other stocked fish species, nuts/oilseeds, and vitamin A-rich vegetables are also positively and significantly associated economic productivity. We also found multiple positive and significant correlations between the productivity of foods and nutrients. Unstocked fish species which enter ponds naturally, such as when water is exchanged, are strongly associated with the productivity of multiple key micronutrients. Productivity of green leafy vegetables is highly significantly associated with productivity of iron, zinc, and vitamin A, as is the production of vitamin A-rich vegetables and other vegetables, but with a smaller coefficient. Production of vitamin A-rich fruits and other fruits has smaller and/or insignificant correlations with most nutrients, as do root crops. The yield of nuts/oilseeds is highly positively correlated with calcium and iron productivity. As expected, rice is an important source of energy and plant protein. Further results show that two unstocked small fish species, Amblypharyngodon mola and tengra, Mystus sp, are particularly significant sources of micronutrients. Consumption of small fish species such as these has been shown to improve intakes of calcium, iron, and vitamin A in Bangladesh. This result underlines the importance of the region’s aquatic biodiversity in supporting human nutrition, with the Sundarbans (the world’s largest contiguous area FIGURE 5. Economic productivity by farming system FIGURE 6. Economic productivity and estimates of nutrient productivity by farming system.
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