Last week, Seafood Watch, the sustainable seafood watchdog program from the Monterey Bay Aquarium, released new and updated recommendations for giant tiger prawns and whiteleg shrimp farmed in Vietnam. The report brings good news for consumers and the environment, as certain farming systems have graduated from Avoid (red) to Good Alternative (yellow) in their ratings.
Giant tiger prawns farmed in rice-shrimp, shrimp-mangrove, or extensive ponds are a Good Alternative, while those produced in intensive ponds are rated Avoid. Whiteleg shrimp farmed in rice-shrimp ponds are a Good Alternative, but those produced in intensive ponds are rated Avoid.
Shrimp is the single most consumed seafood in the United States. In 2017, 1.5 billion pounds of shrimp, much of it traveling from South and Southeast Asia, arrived on American plates. Since then, Seafood watch has made significant progress to measure and improve the environmental, economic and social sustainability of Asian shrimp farms.
The new assessment covers four production systems: intensive ponds systems and three types of extensive pond systems. When they last assessed shrimp in Vietnam in 2017, they consider only three categories: extensive ponds and shrimp-mangrove ponds for giant tiger prawns and intensive ponds for whiteleg shrimp, all of which were rated Avoid (red).
“In these new assessments, we were able to break down extensive ponds into three sub-categories largely thanks to better data availability,” says Cory Nash, Seafood Watch outreach manager. “In-country projects and improved industry relationships have also improved our understanding of these systems. This change in scope helped drive some of these ratings to Good Alternatives.”
A shrimp farmer in Vietnam.
The report covered three types of extensive ponds: (1) improved extensive ponds; (2) shrimp-rice ponds, where both shrimp and rice are grown together on a rotational basis depending on seasonality and salinity levels, and (3) shrimp-mangrove systems, a type of silvoculture that combines shrimp production and mangrove forestry.
In intensive pond systems, farmers provide feed and actively manage ponds at varying degrees of intensity using tools like water treatments, mechanical aeration, and chemicals. This system generally has a higher stocking density (more shrimp per pond). Extensive pond systems, on the other hand, usually have a lower stocking density and use minimal to no feed or chemicals. Instead, they make use of natural tidal cycles or crops to provide food and water maintenance.
Two types of shrimp-rice systems exist in Vietnam: rotational rice-shrimp systems where the two crops are produced consecutively/separately in the paddy fields/ponds, and secondly, in combined co-culture systems where both crops are produced at the same time with ditches and platforms in the ponds for the shrimp and rice respectively.
“Shrimp farming systems like shrimp-rice and mangrove-shrimp ponds usually have a lower stocking density and use minimal to no feed or chemicals, unlike intensive shrimp farms,” says Nash. “Instead, they make use of natural tidal cycles, habitats, or crops to provide food and water maintenance. These ponds in Vietnam are now rated Good Alternative according to the Seafood Watch sustainability rating scale. And we hope that many of these systems can progress to a green (Best Choice) rating in the near future.”
In the combined production of shrimp and mangrove forestry, stocking densities are low, external feed or fertilizer is not used, and the shrimp feed on natural organisms within the pond. Water is exchanged tidally. Shrimp yields are 300–400 kg per hectare per year, and the mangrove trees are harvested at 10- to 20-year cycles.
An extensive pond system for farming shrimp sustainably in Vietnam.
“Mangroves are fantastic at stabilizing the soil against erosion, buffering against climate change, and providing habitat for many species, including the native prawns,” says Nash. “When shrimp farming can co-exist with mangrove buffers and forests, sustainable production can flourish. However, verifying that mangroves aren’t intensively cut down in favor of shrimp production remains a challenge.”
As consumers, however, it’s often difficult to know where seafood comes from. The seafood supply chain is complex, and the lack of traceability is a huge obstacle the industry needs to improve. “This lack of transparency is the reason that we encourage consumers to ask, ‘Do you sell sustainable seafood?’” says Nash.
“You can also ask: Where is the seafood from? Is the seafood wild-caught or farmed-raised? How was the seafood caught or farmed? Your questions let businesses know they should sell seafood caught or farmed in ways that don’t harm the environment.”
Consumers can also refer to Seafood Watch recommendations and guides to help them make sustainable choices.