The area of shrimps farmed in the Tam Giang Cau Hai Lagoon expanded dramatically from 1995 to 2004, but then declined
steadily. An exploratory investigation of the shrimp supply chain conducted in 2009 revealed that well- established relational
contracts between shrimp farmers and wholesalers had succumbed to environmental risk following persistent and
widespread outbreaks of disease in the Lagoon. These outbreaks have been attributed to water pollution, which - in turn -
has been linked to the rapid expansion and intensification of shrimp production. While privatisation of the lagoon bed
encouraged farmers to adopt more intensive production methods, over- intensification can be attributed to the open access
nature of lagoon water, which allows farmers to externalise the cost of their water pollution. This study evaluates a range of
pollution abatement instruments against well-known criteria and concludes that transferable quotas for shrimp seed would be
the most effective policy instrument given prevailing social, institutional, organisational and political conditions. Even so, the
introduction and administration of seed quotas pose major challenges that would require co-management with local user
groups