Assessing and modelling farmers ’ decision- making on integrating aquaculture into agriculture in the Mekong Delta

Contrary to the global trend of specialization within agriculture, the rice-based Vietnamese production systems have diversified into integrated agriculture–aquaculture systems. Economic liberalization in 1986 resulted in an explosive increase in rice production and a rapid diversification. This paper describes the history and dynamics of these systems in the Mekong Delta, and the farmers ’ decision-making in this process. Subsequently, we use fuzzy logic to simulate farmers ’ decisions to opt for no aquaculture or one of four fish-production systems: waste-fed, pellet-fed, rice–fish, and ditch–dike, i.e., fish–fruit. In a reaction to changing market opportunities the farmers developed these systems either from the depressions left after building a homestead or after raising dikes to improve irrigation and drainage for rice and fruit trees. The decision-making was simulated in a two-level hierarchy decision-tree. The first layer handles the farmer’s production preferences for rice, fruit or fish, with composed variables for land, water, labour, capital and market. The second layer simulates the choice between five options: no fish, and the four alternative fish-production systems. The model allowed a farmer to prac-tise different aquaculture systems at the same time. The fuzzy model simulation predicted the frequen-cy distribution of fish production systems fairly accurately, but performed poorly when classifying indi