Striped Catfish Farming
Mekong Delta
Striped catfish, also known as pangasius, tra catfish, basa, and sutchi catfish, in the Mekong Delta, Việt Nam, is one of the fastest-growing species and the third most important freshwater aquaculture species.
In the wild, the natural distribution of the species was restricted to a small geographical area in Việt Nam, Thailand, Lao, and Cambodia in the Mekong and Phraya River basins. Wild populations of striped catfish face threats from over-exploitation, habitat degradation including changes in water quality and flow, and fragmentation of river habitat. Wild striped catfish was once an important fishery and food source in Cambodia, Lao, Thailand, and Việt Nam but is in serious decline. Striped catfish wild populations in their native range are listed as Endangered on the IUCN Red List as it is declining fast in the water of its origin. As a result, the species in the wild mainly persists from escapee or semi-captive populations.
Striped catfish is groundfish, meaning, living and feeding near the bottom as well as in midwaters or near the surface, typically living within the ranges of PH 6.5-7.5 and 22-26 Celsius. The species is a large, fecund, fast-growing omnivore, feeding primarily on algae, plants, zooplankton, insects, fruits, crustaceans, and trash-fish.
Striped catfish seems almost custom-made for life on a fish farm. It can tolerate far greater stocking densities than other catfish species – up to 70 fish per square meter – and can gulp air if pollution and overcrowding drive oxygen in the water too low.
Việt Nam is the source of more than 90 percent of the world’s striped catfish exports, which has increased 50-fold in the last decade. The majority of striped catfish is farmed in 23 square miles (641,203,200 Square Feet) of ponds across nine provinces of the Mekong River Delta. From the 1940s to the 1990s, only a handful of small-scale commercial farms dotted Việt Nam’s Mekong Delta. But in the early 2000s, the industry grew explosively thanks to new aquaculture techniques and booming demand overseas.
In recent decades, striped catfish has been translocated for aquaculture to Bangladesh, India, China, Indonesia, Myanmar, Nepal, Pakistan, and many more countries.
Three production systems dominate in striped catfish farming: ponds, cages, and net pens. Striped catfish are mostly produced at a large scale from large ponds having a depth of over 2 m. In comparison with ponds, cages allow higher fish densities and have higher productivity. The density of cages is high in areas where the water is deeper and the current is stronger.
As captive breeding developed, aquaculture of striped catfish expanded, particularly in Việt Nam and to a lesser extent in Thailand and Cambodia, taking advantage of abundant spawning producing relatively large numbers of larvae that are easily harvested from flowing rivers, ponds, tanks, and cages.
Thankfully, the availability of captive breeding technology has reduced pressure on wild stocks and fish production is booming, but long-term broodstock management is still a work in progress. In the past and still in practice today, broodstock selected for induced spawning must weigh at least 1.75 kg for females and 1.5 kg for males. Females take at least three years to reach sexual maturity in captivity (being then over 3 kg in weight), while males often mature in their second year. A mature female can spawn over one million eggs. Broodstock is discarded when they reach 10 kg or when the relative productivity (number of viable eggs produced) is less than 5 % of the female weight. Hatcheries normally recruit new broodstock on a regular basis every two to three years; new broodstock is obtained both from grow-out farms and the wild. Striped catfish farming needs continuous research agency or industry-led breed improvement program such as occurs for other major aquaculture species. Genetic improvement programs on catfish have started in 2007. Some of the main purposes of the program were to select breed and production of hybrids with closely related species to counter climate change, including for salinity tolerant strain of striped catfish.
Striped catfish is one of the three top consumed freshwater fish types (after carps and tilapia) having extensive supply chains and markets covering over 135 countries in the US, Europe, and Asia. Asian has been the 3rd biggest consumer of Vietnamese striped catfish. The striped catfish from Việt Nam has become an affordable “white fish” in the Western world, and it is acceptable on the huge global market for cheap white fish. In Việt Nam, most production is exported.
Challenges and Improvement needed
The impact of floating fish farms is another challenge facing the Mekong delta because farmers use hormones and fertilizers to grow the fish faster than the normal growth rate, polluting the water, which then causes other farmers downstream to introduce even more external chemicals. Per kg striped catfish produced, waste containing 46gm nitrogen and 14gm phosphorus is produced. About 70% of striped catfish farmers discharge untreated effluents to the river. The remaining 30% of farmers discharge to rice fields or gardens, where part of the nutrients is reused.
Discharging effluents pollute surface waters and increase the risk of horizontal disease transmission. Survival in striped catfish ponds is less than 70% mainly due to disease. More than 15 diseases/syndromes are commonly occurring in striped catfish farming.
Sustainable farming of striped catfish depends on good management of in-pond farming waste. Expanding farming and intensification, without following Best Management Practices (BMP), can lead to the accumulation of large amounts of organic waste in the pond bottom. This waste cannot be utilized by the phytoplankton and its oxidation exhausts the dissolved oxygen deep in pond bottom soils, forming toxic metabolites thereby contributing greatly to deteriorating water quality and incidence of diseases.
To overcome these problems and satisfying international market requirements on fish quality, striped catfish consumers and producers are expected to become more aware of whether the producers are applying sustainable production methods utilizing BMP. These methods start with managing the pond environment to reduce pathogenic bacteria loads, thus reducing fish diseases and accelerating the removal of waste compounds.
Under climate change, environmental parameters most likely to affect striped catfish productivity are increased temperature variation, precipitation, shrinkage of the freshwater zone, as the result of sea-level rise.
Escaped farmed striped catfish can compete with wild fish, throwing ecosystems out of balance. Wild striped catfish also suffer when their food sources are co-opted to make farmed striped catfish feed. Additionally, the health problems that plague striped catfish farms often lead to the inappropriate use of veterinary medicines and chemicals, which can negatively impact wild fish stocks, the environment, and human health.
