Aquaculture smells fishy

  • The severe health implications of eating commercially farmed fish

Feb 19, 2017-

Now that the Ministry of Agricultural Development has announced that it is emphasising commercial fish production, consumers should know the repercussions of eating these fish. Farmed fish are hosts for harmful entities such as sea lice, viruses, chemicals, antibiotic residues, and antibiotic-resistant bacteria. 

In a typical aquaculture facility, fish eggs are hatched in a hatchery. Once hatched, the young fish are transferred to inland ponds, or sections of the sea separated from the main body by nets. To increase production and profits, the density of fish in these enclosures is kept very high. The owners tend to keep adding fish to enclosures until they start dying off. It is only when the rate of death increases beyond 30 percent that the stocking stops. 

These fish are so crowded that they resemble poultry farm chickens that spend their lives huddled in tiny cages where even wing movement is prohibited. In these fish farms, a 2.5-foot-long salmon is typically allotted four feet of water during its entire life. Trout farms are even more crowded with 27 fish packed into four feet of water.

Bacterial growth

Just as children get head lice in crowded boarding schools, fish also suffer from a similar problem of sea lice. Sea lice are marine parasites that feed on the mucus, skin tissue, and blood of fish. Sea lice have an extremely high productive capacity, with an adult female sea louse producing 6-11 egg strings of 1000 eggs each. 

These lice move between fish.

In severely crowded conditions such as the ones presented by fish farms, sea lice move rapidly among fish and have the capacity to consume fish flesh down to the bone. Lesions appear on the body as the lice eat the scales. Once the fishes are killed, the lice remain in the body. This problem exists in farmed fish all over the world. In 2012, the Canadian grocery chain, Sobey’s, had to pull out all the fish from its shops after sea lice were found in them. In Scotland, government inspections showed farms with a minimum of 44 lice per fish.  Irish “organic” farms showed between 54-71 sea lice per farmed salmon—over five times the government’s allowed maximum. If this is the case in countries with strict quality checks, imagine what happens in India where there is no checking of farms.

Furunculosis bacterium has been found in sea lice. This bacterium is also known as staphylococcus aureus; the bacterium afflicts humans with pus filled boils or furuncles on the human head and can increase in severity to the point where an individual may get a fever, swollen lymph nodes, and fatigue. 

Chemical overdose

Instead of reducing the fish in the inland ponds, fish farms deal with the problem of sea lice by increasing the toxic pesticides poured into the water. In the last 10 years, use of these poisonous chemicals has gone up 10 times. Pesticides administered to control sea lice include organophosphates which cause cancer in humans. Dichlorvos was used for many years and was replaced by azamethiphos. Both cause human mutations. 


Cypermethrin and deltamethrin are the two pyrethroids commonly used to control sea lice. In humans these cause difficulty in breathing, tremors, incoordination, rash, lower sperm counts, and breast cancer. The main drugs used are avermectins. Since these drugs are toxic for humans, the fish farm is supposed to stop them 175 days before killing the fish. But who’s counting?

Amoebic gill disease is another problem in most fish farms. As the most prevalent disease, amoebic gill disease is potentially fatal and is caused by the amoeba Neoparamoeba perurans. To bring down the mortality rate, levimasole, which is used to deworm cattle (and administered as an anti-cancer drug for humans), is added to the water at 10 parts per million. Chloramine and chlorine dioxide are also used.

Since the fish are crowded and living in chemical waters, they are so physically stressed that their immune systems are weakened, making them prone to  numerous infections. With the limited space, fish rub against each other and the sides of cages, damaging their fins and causing infections. Aquaculture operators use strong antibiotics to control these infections. The most frequent fish infections treated with antibiotics are skin ulcers, diarrhea, and blood sepsis. The micro-organisms responsible for these infections belong to bacterial families that also produce infections in humans.

These antibiotics are administered to the fish in the feed, baths, and as injections. An unlimited amount of oxytetracycline and flumequine is used, and this stays in the body. One study has found up to 578.8 milligrams of oxytetracycline and flumequine per kg in trout and sea-bass farms. 

The antibiotics used in aquaculture, either for prophylactic or therapeutic purposes, accumulate in the tissue of aquatic animals. When consumed by humans, these drug residues cause allergies, toxic effects, and changes in the intestinal microbial fauna. The residue of chloramphenicol in food consumed by humans can even result in aplastic anaemia, which leads to very serious bone marrow diseases. Nitrofuran antibiotics are also used, and are known to cause cancer in humans. So, not only do humans get bacteria with their fish, they also consume antibiotics. 

Bacteria also tend to develop a resistance, with salmonella and E Coli bacteria identified as the first to become antibiotic resistant. Evidence shows that the bacteria Typhimurium DT104, which is a cause of salmonellosis in humans and animals, originated in fish farms in Asia which use florfenicol extensively. 

Antibiotics in farmed fish also cause allergies and poisoning. The use of antibiotic quinolones is unrestricted in countries with growing aquaculture industries, such as India, China, and Chile. For example, in Chile, statistics indicate that annually 10-12 metric tons of quinolones are used in human medicine and approximately 100-110 metric tons of these antibiotics are used in aquaculture. These broad-spectrum antibiotics have serious side effects associated with tendinitis and tendon rupture, causing permanent disability. Nervous system effects include insomnia, restlessness and, in rare cases, seizures, convulsions, and psychosis. Common side effects include gastrointestinal effects such as nausea, vomiting, and diarrhoea, as well as headache and insomnia. 

Chemical fertilisers and pesticides are used widely in fish farms. The fertiliser is used to increase the growth of fish food and they remain in the body of the fish. A piscicide is a fish poison used to eliminate a dominant species of fish in a body of water, as the first step in attempting to populate the body of water with a different fish. They are also used to combat parasites. Piscicides are widely used in India. So are formalin and malachite green, commonly used as disinfectants. Malachite green has been reported to cause cancer, physical abnormalities, and lung collapse.

Fish farming has more than tripled within the past 15 years. Do you want to risk eating them?

To join the animal welfare movement contact gandhim@nic.in, www.peopleforanimalsindia.org

Published: 19-02-2017 08:50

User's Feedback

Click here for your comments

Comment via Facebook

Don't have facebook account? Use this form to comment