Is formalin present in your fish? Here’s how to buy unadulterated seafood

With fear over reports of formalin in your fish, arm yourself with basic tips on how to identify fresh fish and minimise risks of buying adulterated seafood

July 16, 2018 12:04 pm | Updated 01:27 pm IST

When foreign news sources spoke about mercury levels in fish, it seemed very far away from our shores. But now, formalin, a cancer-inducing chemical used illegally to preserve fish, is right here: in our markets, in the curries we eat at home, in our bodies. ( Refer to The Hindu report dated July 9, 2018).

Rather than falling prey to fear and issuing a complete ban on bringing home this important source of nutrients (iodine from sea fish, healthy fats, vitamins A and D, phosphorus, magnesium, selenium) here’s what we can do to minimise risks of picking fish with harmful chemicals.

Ask questions

Get to know your fishermen and women. And ask them questions about where and how your fish was caught. This means avoiding shopping in supermarkets. Building a relationship of transparency and trust with the people who produce and sell your food is the only way to ensure pure, unadulterated food supply chains. Try and source directly from small-scale fishermen, who catch seasonal fish, and supply you with local varieties. This advice is comparatively easy to follow if you live along the coast.

Choose alternatives

Shouldn’t the smell of formalin raise red flags? Typically, formalin has a strong smell, which should immediately put off consumers. However, most of the formalin used to preserve seafood is diluted to the extent that the smell is not easily detectable.

Furthermore, because it is injected deep into the flesh, the smell may not become apparent until we cut into the flesh. It is only worth investing this time for varieties that give really high returns, that is, high value and popular varieties of seafood. Therefore, choosing alternatives to popular varieties will reduce your chances of encountering formalin-laced fish.



Some fishmongers point to red gills as the way to detect whether fish is fresh. Differentiate between reddish-maroon, which reflects freshness and maroonish-black, which is a sign of starting decay. However, when formalin is used in a fish, the fish retains the red coloured gills. Red gills could be a false symbol of freshness. So gauge the appearance of the fish as a whole.


Many fishermen and fish traders never take care to preserve anything other than the meat, whether in ice or using formalin. Therefore the condition of the fins and tail will immediately reveal the freshness. If the fins have started to shrivel and decay, then avoid the fish. It is easy to miss the fins, because they remain folded, and are often the first part of the fish to be cut off, but insist on seeing them spread out, so you can tell whether the fish is fresh.


Really fresh fish have clear eyes. The eyes of fish that have been dead for over two days start becoming cloudy. If your fish comes from small-scale fishermen, you are likely to have fish with clear eyes, since they often do not have the capacity to go out fishing for more than two days.


A third characteristic is the firmness of the raw meat at room temperature. The meat should be firm and offer resistance to pressure, but not be rubbery. If it is rubbery, that suggests formalin preservation; if the flesh is soft, it suggests that decay has started to set in. Fish that are freshly caught from the sea still have a layer of mucous over their scales. Once the scales have started to dry out and feel more like sandpaper, you can tell that the fish is old.


Fresh fish do not smell fishy. The fishy smell that we associate with seafood exists only in fish that have started to decay. Instead, fresh fish have the salty smell that we associate with clean seas. At the same time, formalin-laced fish may not have a fishy smell, so the way to distinguish between formalin-contaminated and fresh fish is to look for flies. As a great seafood eater and wildlife biologist, hailing from Kerala says, “Always go to the fish shop with flies, because the flies can tell whether the fish have been contaminated.”


What is seafood?

One of the main issues that allows the proliferation of unsavoury practices in seafood storage is the fact that many consumers lack knowledge about what it is that they are eating. If a prawn or a fish is cultured in a pond on land, can it be considered seafood? If this prawn has never even seen the sea, let alone grown up in it, on what basis do we call this seafood? At this juncture we make a clear distinction between aquatic animals grown in aquaculture and real seafood that was caught from the sea. Therefore, the same distinctions need to be made when discussing the problem of adulteration in what is being reported as seafood.

Reports of the presence of formalin in seafood have discussed adulterants in detail, but rarely focus on what is being adulterated. In 2011, a report from Delhi focussed on the presence of formalin. In 2014, there was a seizure in Kerala, contaminated with both ammonia and formalin, and in 2016 this issue arose in Mangalore. These reports described in detail the effects of the adulterants:

    • Ammonia is typically used to slow the melting of the ice, but is corrosive and could permanently damage human intestinal tissue at high concentrations.
    • Formalin is used to preserve the fish itself and is typically injected into the fish or prawn. Formalin, or formaldehyde, has both short- and long-term impacts on health. In the short term it poses a risk of spontaneous abortion for pregnant women and also lowers immunity. In the long term it can decrease fertility and has been identified as a carcinogen.

In other news

Twenty eight tonnes of fish and prawns preserved with formalin were seized from across the country last month. Reportage of this seizure featured pictures of species as varied as sailfish and sardines. In fact, the offending seizures consisted of prawns, and freshwater fish from aquaculture. Some past seizures have implicated the most high-value varieties of sea fish but the majority of the seizures have been grown in farms for aquaculture. Therefore one easy way to reduce your chances of eating formalin-laced fish is to choose real seafood over aquaculture grown food.

(Divya Karnad and Chaitanya Krishna co-founded InSeason Fish, a sustainable seafood initiative)

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