A cost-benefit analysis of small-holder floating-house fish farming in Chau Doc City, Vietnamese Mekong Delta

Smallholder floating-house aquaculture supports vital riverine livelihoods in the Vietnamese Mekong Delta but faces increasing environmental and hydrological pressures. This study conducts an empirical Cost-Benefit Analysis (CBA) to evaluate the economic viability, cost drivers, and adaptation strategies of smallholders in Chau Doc City in An Giang Province. Primary data were gathered through semi-structured interviews with 35 fish farmers across three distinct river reaches. Enterprise budgets standardized to a modal cage capacity of 128 m³ revealed marked spatial disparities in profitability. Smallholders operating along the Chau Doc and Bassac Rivers generated positive net returns (mean USD 5,833 and USD 6,101 respectively), benefiting from favorable natural flow dynamics that lowered feed and veterinary medication expenditures. Conversely, farms at the River Intersection operated at substantial net losses (-USD 7,132) due to excessive cage volumes, hydraulic turbulence, and debris accumulation that created severe diseconomies of scale. In response to yield declines reported by 68.6% of respondents, farmers deployed autonomous adaptations, including peripheral aquatic plant bio-buffers, compressor-hose diving for seasonal cage relocation, and diversification into resilient or high-value species such as eels. Furthermore, operations depend heavily on unpaid household labor (74.3%) and face demographic vulnerabilities, with over 91% of primary operators aged 30 or older and predominantly male (77.1%). Policy interventions must prioritize localized water governance, tailored risk-management credit tools, and succession initiatives that engage women and youth to secure long-term livelihood resilience.