Sunday Express 

A bone to pick
Thursday April 20 2006 17:21 IST

Maneka Gandhi

Because the oceans of the world have been decimated by over-fishing and rivers are increasing being polluted, people are beginning to eat more farmed fish. When you eat farmed fish you don’t just eat a creature brought up in a sterile pond. You also eat the dead bodies and manure of chickens, pigs and ducks.

The United Nations Food and Agriculture Organisation calls this system ‘Integrated Livestock Fish Farming’ and says it should be done in developing countries to help the poor get protein. In spite of the Mad Cow crisis when cattle were fed sheep meat, no one seems to be worried about the feeding of faeces to fish which will be consumed by humans.

Few people know that most pond-fed farmed fish in India are fed on a diet of human waste and sewage. And the countries that use human faeces to feed fish are India, China, Sri Lanka, Malaysia, Korea, Indonesia, and Nigeria.

I have seen how it works. Small plots of dug out land are given on contract to poor people in the villages for fish farming. These aquaculture ponds are stocked with fish, and used as bathrooms by the owners and their friends, to wash cattle, and throw manure into. Every few weeks, the fish are taken out and sold in the local market. The ponds stink and are covered with a green slime. Basically these are toilets that pay for themselves - an economic sulabh shauchalaya.

Raising fish on excreta, nightsoil or wastewater is encouraged by fishery experts, (bureaucrats who come around once in a while) as it is ‘‘natural food’’ for fish. It does not matter that human or animal faecal solids, use of raw sewage or fresh nightsoil in fish ponds should be prohibited for health reasons.

A wide range of fish species have been cultivated in aquaculture ponds receiving human waste, including common carp, Indian major carps, Chinese silver carp, pighead carp, grass carp, crucian carp, Nile carp, tilapia, milkfish, catfish, kissing gouramy, giant gourami, silver barb and freshwater prawns. The selection reflects local culture rather than fish optimally suited to such feeding. For example, Chinese carps and Indian major carps are the major species in excreta-fed systems in China and India. Tilapia are better suited to excreta-fed systems but carp is eaten more as is milkfish which does poorly in these adverse environmental conditions.

Many of these ponds that are fertilised with human excreta grow duckweed which is used not just as feed for carp but also for chickens and ducks. Every now and then the overload of excreta and toxic sewage hits the oxygen supply and all the fish come belly up. Ever so often you hear of thousands of fish dead in lakes that are fed with the town’s sewage. This happens mainly at night when the phytoplankton have higher rates of respiration and so the dissolved oxygen in the water becomes less. The phytoplankton develop as a result of the nutrients contained in the waste. Phytoplankton provide feed for the largest percentage of fish farmed in Asia.

Fish also die when the bacterial load becomes too much for their frail bodies to bear. One of the main reasons for ponds ‘‘failing’’ is high ammonia concentration in the waste thrown into the pond. After both sewage and faeces have large amounts of urea and urine. Ammonia is toxic to fish in the concentration range 0.2 - 2.0 mg/l. However, the tolerance of different species of fish varies, with tilapa species being least affected by high ammonia levels. In ponds receiving large quantities of ‘‘organic matter’’ (this is the scientific term used by the industry for excreta and sewage so as not to drive you away!), sediments accumulate and release chemicals such as methane and sulphides.

Though dissolved oxygen is essential to the fish at 5 mg/1, the level in excreta-fed ponds is usually at an absolute minimum of a little less than 1mg/l leading to many other diseases that are undetected by the fish grower but will show up in the fish eater.

Scientists say that, while yields are satisfactory from waste fed fish ponds, higher yields could be achieved if the fish were fed other foods such as cereals. They also say pond nutrition needs to be diversified from just faeces. I could have told them that! How much weight can a fish put on by just eating excreta? But this is not going to happen ecause cereals cost money and excreta is free.

What are the health impacts of eating sewage and human faeces via fish? For one, human faeces is very toxic in itself. Sewage has heavy metals and persistent pesticides in it and these concentrate themselves in the body of the fish. Today fish are the largest PCB (a set of carcinogenic chemicals), heavy metal and mercury carriers in the world. Fish that eat algae, phytoplankton, duckweed that eat the faeces and sewage accumulate heavy metals and poisonous chemicals just as fast in these sewage ponds.

Do you think a fresh healthy fish smells? Nope. The ‘‘fishy’’ smell you get is the chemical smell of a rotting body. A high phenol content in the sewage fed to fish ponds in Wuhon, China, caused the fish flesh to smell of phenol.

Have you even looked at the fish you buy? A 1989 study done on the effects of municipal wastewater on three species of fish confirmed that even moderately toxic effluent caused cardiovascular and skeletal defects, depression of heart rate and lower growth rates.

What does your faeces carry? Pathogens so toxic that the fish becomes a smelly living time bomb. Human excreta contains menstrual blood, urine, hormones, bacteria, viruses, protozoa and worms - and of course all the diseases the human is carrying from diarrhoea to tuberculosis to diabetes to cancer. Waste water or sewage contains fat, oil, metals, chemical substances from everything ranging from soap to paint and industrial waste water.

Scientists have came up with an answer to that. It’s called Depuration - a process whereby the fish is “made acceptable for the market” by holding in clean-water ponds for several weeks at the end of the growing cycle. However, depuration doesn’t work because most of the owners of ponds don’t have the space and the ability to get pure water - they simply net the fish from the waste water pond and send it to market. Also, experiments on depuration show it doesn’t work on heavily contaminated fish.

The Indian Council for Agricultural Research (ICAR) says river fish are beoming rarer - of the 34 lakh tonne fish production in India only 2 lakh comes from rivers, the rest from manmade fisheryponds. The Indian Institute of Oceanography has found human faeces in all the fish in India. This is what we call progress - humans paying to eat their own and everyone’s else's faeces.

Bon appetit.

The writer can be contacted at

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