OTHER ENVIRONMENTAL ISSUES

Disease

Crumlish et al. (2002) identified the bacteria Edwardsiella ictaluri, a disease native to North America and Ictalurid catfish, in farmed river catfish cultured in the Mekong River Delta.

This was the first time this disease was recorded in Pangasiid catfishes. As yet it is not known whether the bacteria was indigenous but previously unknown, or if it was introduced from overseas. There are no data as yet to show that wild stocks have been affected by this disease. Additionally there is no evidence to suggest that wild Pangasiid stocks are suffering more disease as an impact of contact with cultured Pangasiid catfishes, particularly those in cages.

Effluent

Monoculture of Pangasiid catfishes in cages which are open net containers, and ponds which are drained into canals and rivers, impact on the natural water environment by increasing nutrient and suspended sediment loads and increasing Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD).

The high water temperatures in the Mekong Delta region of Viet Nam allow primary consumers to proliferate which rapidly break down ammonia, nitrates, and organic matter released in faecal wastes from Pangasiid cages and ponds. However despite this, anoxic conditions can occur in localised areas where there are more cages and ponds than the carrying capacity of the area can sustain.

Other issues

Diseases and water quality issues pose serious threats to the future of the industry. Export markets will in the future increasingly demand that products live up to both product quality standards as well as social and environmental sustainability standards. If Viet Nam’s current level of export is to be maintained (and, according to official targets, even increased) standards will have to be developed and implemented for the industry. The Sustainable Aquaculture Group of Viet Nam is proposing to commence a study on the Pangasiid production carrying capacity of the Mekong Delta region of Viet Nam in 2008.