Shrimp farmers perceptions on factors affecting shrimp productivity in integrated mangrove-shrimp systems in Ca Mau, Vietnam

Vietnamese mangroves in the Mekong Delta have been degraded and lost by war, coastal development and aquaculture since the 1950s. However, to promote replanting and support local livelihoods Ca Mau province issued 20-year mangrove leases to local farmers in 1991 for 70:30 forest:exploitation, which was later changed to 60:40 in 2010. Extensive integrated mangrove-shrimp systems were particularly attractive to poor farmers and understanding their perceptions on factors affecting productivity as well as socio-economic, technical and financial characteristics can aid solutions to better management. Shrimp productivity is variable and concern from the local producers that this could be because of age of mangrove stands in the systems led to this study. Forty-six households were selected at random based on different mangrove ages (2–4, 5–7, 9–12 and > 12 years old) in Lam Hai commune, Ca Mau province. The structured questionnaires with both quantitative and qualitative methods, a participatory approach, principal component analysis (PCA), and analytic hierarchy process (AHP) were employed to evaluate the effects of mangrove ages on pond environment and shrimp productivity. The average farm area was 4.9 ± 1.9 ha, with forest:exploitation ratio of 60:40. Mean shrimp productivity was 188.1 ± 94.7 kg ha−1 yr−1 and this was not significantly different between the four ages of mangrove systems. High variable costs of pond dredging meant the lowest profit margin was recorded in >12 years old mangrove stands but the highest profit margin was found in 9–12 years. Water level management was identified as a key factor in stepwise regression analysis. The farmers’ responses to the criteria for integrated mangrove-shrimp pond management under different mangrove age systems differ and are discussed.