Catfish farming in Viet Nam – the challenges of change
In the Mekong Delta of Viet Nam, the farming of catfish (Pangasianodon hypophthalmus), also known as tra, sutchi, Pangasius, and striped catfish, has been hailed as a global success in aquaculture production. The sector currently produces over 1.2 million tonnes of fish in a pond acreage of less than 6 000 hectares (ha) and employs over 170 000 people. In 2009, it generated an export income of over US$1.4 billion. This success has triggered the development of subsidiary sectors for feed production, food processing and waste recycling. This boom in production, which has occurred within a relatively short period of time, a decade or less, has transformed traditional backyard farming into a vibrant commercial activity. Over 97 percent of the final product is exported to over 100 nations and territories (De Silva and Phuong, 2011). Catfish production has provided an acceptable alternative ‘white fish’ in global markets (Duc, 2010; Little et al., 2012).
An increasingly efficient farming system with a comparatively lower carbon footprint
Catfish farming is the highest yielding activity in the primary production sector. The global average is 250 to 400 tonnes per ha per crop. The table below gives details on the estimated protein and fishmeal usage in the sector. Catfish farming uses only 146 600 tonnes of fishmeal and no fish oil.
Total Production | 1,200,000 t | De Silva and Phuong, 2011 |
|---|---|---|
Average FCR (feed conversion rate) | 1.45 | Phan et al., 2009 |
Total feed used | 1,740,00 t | |
Average protein content in feed | 26-30% | |
Total protein used for production | 487,200 t | |
Estimated fish meal used in production | 146,160 t | If 30% of protein derived from fish meal |
From 2005 to 2010, catfish processing improved significantly. About 1 kg of processed product was derived from 1.69 kg of fresh fish, and overall ‘waste’ was reduced. This waste is converted into fish oil and fishmeal, which is used as animal feed. It is not dumped in landfills and other forms of disposal. At least three of the country’s biggest processing plants are involved in this activity.
Catfish farming has been criticized by some environmentalists who claim that it uses excessive amounts of feeds and produces excessive effluent discharge. However, this criticism is not backed by scientific evidence. Little et al. (2012) show that from a comparative perspective, the environmental impact of catfish farming in Viet Nam is relatively low. Also, the overall emissions from tra catfish farming contributes less than 1 percent of total suspended solids, nitrogen and phosphorous in the Mekong Delta as whole. For an activity that produces over a million tonnes of food and generates a revenue in excess of US$1 billion, this level of discharge is miniscule (De Silva and Phuong, 2011).
The mean water consumption was of farm volume of approximately 6.4 megalitres per tonne with a discharge of 3.4 megalitres per tonne. This level of water consumption is much lower than for shrimp farming in ponds, (11-43 megalitres per tonne) and the tank culture of salmonids (252 megalitres per tonne) (Beveridge et al., 1991). Phan et al. (2009) estimated the total water consumed in 2007 was that 4 371 gigalitres (one billion litres), based on 683 000 tonnes of catfish production in the whole of the Mekong delta. Out of this total, 2 754 gigalitres was discharged back to the river. The amount of water used for producing of a tonne of catfish was 4 023 cubic metres, or four cubic metres per kg. In North America, catfish farming in ponds uses an estimated 40 cubic metres per kg. The reduced level of water consumption per unit of product in Viet Nam is an indication of the high intensification of production. It is interesting to note that water lost through evapotranspiration in rice cultivation is estimated to be around 1.7 cubic metres per kg of rice, but productivity of rice is 4.5 tonnes per ha and with an export of 115 kg of nitrogen per ha.
The water and nutrients lost through drainage from aquaculture ponds can be used to irrigate or fertilize crops, either on dikes or in adjacent fields (Prein, 2002). In stagnant systems, (e.g. ponds that are extensively fed or aerated), drainage is irregular and limited at maximum to a few days per year. In such systems, the use of drainage water is impractical for crop production, unless the drainage water can be stored in a deep reservoir for later use (Mires, 2000). Nevertheless, small-scale farmers often consider their pond primarily as a reservoir, from which water can be drawn daily for crop or animal production and household use (Luu, 1999). By integrating aquaculture and water storage, the water for aquaculture is shared with other farm activities, which greatly increases water use efficiency in the sector.
The resilience of catfish farming has been tested primarily by market forces. The sector, which continues to thrive, provides a classic example of the effective recycling of waste and has a relatively low carbon emission scenario compared to most primary production sectors.
The Mekong River has the eighth highest discharge of all major rivers in the world. Catfish farming is done in the lower reaches of the delta where water resources are plentiful. This enables the sector to operate effectively and reap high yields. However, expansion of the farming area and greater intensification of production may not be possible. A further reduction of the discharge levels to the Mekong River will be a crucial factor to the sector’s sustainability.
Is catfish farming in Viet Nam well adapted to climate change?
This highly productive aquaculture system may not be well prepared to face climate change. Rising sea levels pose a real threat in the lower Mekong. Catfish farms may be exposed to increased salinity in the mid and long term. In the short term, catfish farming may be sensitive to some climate change variability and trends. For example, increasing temperatures and changes in the hydrological patterns may trigger disease outbreaks. A tight biosecurity framework is currently not in place, and given the high density of farms and very high density of fish production, a disease outbreak could devastate the sector.
Catfish farming can become more climate-smart through the better planning of farm locations, improved water and nutrient management, and enhanced integration with other farming systems. However, a more urgent measure is a tighter biosecurity framework. Catfish farming can also become more climate-smart by implementing an ecosystem approach to aquaculture that would ensure the participation of all stakeholders and improve their understanding of climate change-related risks and prevention measures. For example, increasing salinity could be addressed by moving farms upstream, although this is admittedly an unlikely scenario. A more long-term approach to adaptation would be to develop catfish varieties that are more resistant to salinity.