Winner, Winner Shrimp for Dinner. A Peek at Aquaculture in Vietnam
By Mary Medley
Bubba was right. Shrimp anyway you want it, and Vietnam is there to provide it. The question remains: how will the shrimp economy, Vietnam’s 4th biggest export grossing $2.2 billion annually, adapt to climate change? The problem does not lay directly in harvesting the shrimp itself, but rather in the environmental and socioeconomic consequences. Mangroves have been destroyed for shrimp mono-cropping, pathogens have been spread, and communities divided. Shrimping can be highly profitable for those involved, elevating families from poverty, but being involved in the business is luck of the draw. Farmers in areas where rice can be cultivated have to grow it even if they would prefer the higher profit shrimp. With issues of salinity intrusion rice productions are threatened, and the government mandates rice sovereignty within the country in order to guarantee food security for Vietnam. So how will farmers supplement their income while meeting the requirements to grow rice and working within the bounds of the environment?
Aquaculture has replaced many mangrove forests in the past few decades. In Soc Trang province mangroves used to extend 2,000 meters inland, now they are a meager 20 meters. Mangrove forests provide a buffer to coastal farmers holding sedimentation and acting as a shield when tropical storms and cyclones haunt the coasts of Vietnam. Unfortunately this protective barrier now acts in patchy fashion. The lands have been exchanged for the economic gain of shrimp cropping. It is as they say, “dong talks,” and farmers in more rural areas can see the tangible effects of more money, but do not realize that short term economic gains will not be sustainable if the Delta along with their homes are under water.
One way to solve this is integrated systems of shrimp farming that works within the mangroves. Farmers can chose to use the natural tidal process and rudimentary dykes to harvest shrimp naturally, and the process requires less inputs of larvae and feeding. When opened at high tidal periods dykes allow the brackish water in, bringing in natural food for the crustaceans. The shrimp even fetch a higher price on the commercial market. Sadly, relaxed law enforcement allows poachers to harvest shrimp in such regions illegally at night. Overfishing has been damaging a well-balanced sustainable system so it’s been up to farmers to meet global shrimp demand.
The export market is not flooded with naturally raised shrimp though. Shrimp on the global market from Vietnam are most likely farm raised. The options on your menu for tonight’s dinner are whiteleg shrimp (Litopenaeus vannamei) or black tiger prawns (Penaeus monodon); both have their benefits and issues. The shrimp start out in a hatchery, with temperature, salinity and oxygen level controls. During their juvenile period a complex feeding system is occurring. Brine shrimp larvae, common to the United States, are being raised to feed their bigger juvenile crustacean cousins. As the whiteleg shrimp and black tiger prawns get larger they are moved into their new homes, farming ponds. Whitelegs take a short 3 months to develop to harvestable size in the pond and black tigers take five. Whitelegs are now more commonly farmed because of their shorter maturity period and their pathogen free nature, but black tiger fetch a higher price on the market and are more desirable. Nets drape over the ponds to prevent the disease spread by birds from leapfrogging from shrimp pond to shrimp pond. Probiotics and lye are used for water quality. Intensive shrimp farming is efficient but it degrades the natural environment and exacerbates the effects of climate change.
Most Vietnamese would prefer shrimp cropping year round. The process is less intensive than rice farming and puts the families in a better financial situation. People more inland where brackish waters don’t reach do not have a choice though; there rice cultivation is necessary. There are new systems of combining rice and shrimp farming. Early in the crop season, August to January, rice is grown and harvested in freshwater. Then during the dry season, the dikes are opened and brackish water fills fallow fields and provides a habitat for growing shrimp. This allows for the rice requirement by the government, but also allows farmers to increase their profits.
Vietnamese farming has been put on the chopping block. The balancing act of meeting global demand and working within the local environment has required aquaculture to become a system dependent on unnatural inputs, so in fact long term nobody in the system is winning. I am hopeful that shrimp isn’t always what’s for dinner, but is still available for the sake of Mekong farmers.