It’s sold in Sweden and other parts of Europe as an inexpensive substitute for the dwindling stocks of cod.
These are farmed in Vietnam in what Swedish Radio News says are very over-crowded tanks or enclosures, and millions of tons of their wastes are reportedly released into the Mekong River. This leads to an over-fertilization that damages the local eco-system, and threatens fish in the river consumed by the local population.
Swedish Radio News says some companies do filter the outgoing water, but the pressure from Europe to keep prices low means that many others cannot afford such measures.
The cultivated Pengasius are also fed meal made from fish caught at sea, which in turn has led to over-fishing there.
The enclosures are just around 50 by 100 meters, which can contain more than 300,000 fish of around 1 kg each. Swedish Radio News says the consequence is that the fish get sick, which has led to the abuse of antibiotics, and the resulting growth in antibiotic resistant bacteria.