How Dense Is Too Dense? Stocking Density, Survival and Welfare on Vietnamese Shrimp Farms
A study in Aquaculture International, co-authored by Chung Thanh Phan (HAPRI Research Associate) and Diem Thi Hong Vo, finds that on Vietnamese shrimp farms stocking density is better understood as part of a management bundle than as a stand-alone welfare ‘dose’. Within this sample, the authors find that universal density thresholds are difficult to justify unless they are conditioned on production system and complementary inputs.
Context
Shrimp aquaculture supports coastal livelihoods and export revenue in Viet Nam. Stocking density is a key intensification choice in the sector, with implications for productivity and animal welfare.
On commercial farms, however, density is not chosen in isolation. It is chosen alongside inputs such as aeration and monitoring, and within distinct production systems, which makes inference from observational data difficult.
Methods
The authors analyse a survey of 210 shrimp farms in Viet Nam covering five systems, from extensive to super-intensive production. Welfare is measured with a composite welfare-impairment severity index, which averages five observable indicators scored 1–5, and with an ordinal feeding-response severity measure. Survival is modelled with fractional logit models that include system fixed effects and flexible density terms, the composite index with ordinary least squares, and feeding severity with an ordered logit model. Internal-consistency, principal-component and leave-one-out checks assess the index, while trimming extreme densities and quantile regressions test the survival results.
Key findings
In simple bivariate comparisons, higher stocking densities coincided with both higher survival and greater welfare-impairment severity.
In the regression models, density effects were imprecise: the survival spline suggests some curvature but no robust overall density gradient.
Aeration intensity remained a positive correlate of survival.
Alternative weightings of the welfare index and models of its individual components did not uncover a gradient between density and impairment severity.
Policy implications
The authors state that the most direct policy implication is that universal density thresholds are unlikely to be credible welfare rules unless they are conditioned on system and complementary management capacity.
Keywords:
Shrimp Aquaculture
Stocking Density
Animal Welfare
Survival Rate
Vietnam
Aeration
Link:
Citation:
Phan, C. T., & Vo, D. T. H. (2026). How dense is too dense? Stocking density, survival, and welfare impairments in Vietnamese shrimp aquaculture. Aquaculture International, 34(6).
