Seafood can contain TOXINS

Heavy metals and carcinogenic contaminants

In July 2020, Hong Kong’s Consumer Council found excessive levels of the following heavy metals in 46 samples of canned seafood:

  • Cadmium, which can lead to chronic poisoning, was detected in 90% of sardine samples and 60% of tuna samples
  • Inorganic arsenic can cause neurologic and cardiovascular diseases and was detected in over 70% of the sardine samples.
  • Polychlorinated biphenyls (PCBs) are carcinogenic and were detected in nearly half of all sardine samples.
  • Methylmercury was detected in over 90% of all tuna samples. It should be avoided by pregnant women as it hinders foetus development and can cause neurological damage.

Source: 46 Canned Fish Samples Found to Contain Arsenic, Mercury, Cadmium, Lead and Other Metallic Contaminants Rich in Calcium and Protein Contents but Beware of Excessive Sodium Intake

Malachite green

In 2019, CFS found 15 out of 70 freshwater fish samples testing positive for malachite green.

Malachite green is an industrial dye used by some fish farms to treat fish diseases. It is both carcinogenic and genotoxic.

Malachite green in all seafood is banned.

CFS found malachite green in frozen Sabah garoupa (marketed as Brown-marbled grouper). Among imported freshwater fish, Chinese perch (Siniperca sp.) contained the highest level of malachite green of 6.9mg/kg.

To avoid malachite green, the government advises us to buy good fish from reputable sources and do not buy fish from illegal hawkers

Source: Cap. 132AF Harmful Substances in Food Regulations,
Malachite Green found in Chinese Perch,
Malachite Green found in Sabah Garoupa

Ciguatera Fish Poisoning (CFP)

Ciguatera poisoning has been intermittently reported in Hong Kong over the last two decades.

It’s caused by the ciguatera toxin found in micro-organisms in the oceans and can occur in coral reef fish sourced from the tropical and subtropical Pacific. The toxin cannot be removed by cooking. It can affect nerve and muscular functions, causing low blood pressure, slow heart rate, respiratory difficulties, or even paralysis in extreme cases.

In Hong Kong, ciguatoxins are most commonly found in live reef fish, such as Squaretail coral grouper, Lyretail, Brown-marbled grouper, Leopard coral grouper, Humphead wrasse, Two-spot red snapper, Moray eels.

Source: Ciguatera Food Poisoning

Mislabeled and unlabeled seafood

To make sure our seafood is legal and safe for consumption, we need proper seafood labelling.

Are you getting what you paid for?

Mislabeling is not uncommon in the seafood industry –
examples in Hong Kong include the Red sea bream sashimi (Pagrus major) mislabeled as Yellowback seabream (Dentex spp.) and Squaretail coralgrouper (Plectropomus areolatus) mislabeled as Leopard coral trout (Plectropomus leopardus), which can sell for a doubled price.

Salmon or Trout?

Salmon or Trout?

In 2018 it was reported that 1/3 of salmon sold in mainland China was actually freshwater farmed rainbow trout.
Although sharing a similar appearance when filleted, academics warn that raw rainbow trout can pass on parasites to humans, and should not be eaten as sashimi.

Source: Backlash after state media reveals ‘imported’ salmon in China is rainbow trout farmed in Qinghai,
In China, rainbow trout is now salmon?

Oilfish or Cod?

Oilfish or Cod?

In 2007, consumption of oilfish (Ruvettus pretiosus and Lepidocybium flavobrunneum) filets mislabeled as “Cod filets” caused oily diarrhea in consumers.
Oilfish contains high levels of indigestible wax esters, which can cause diarrhea. In severe cases, nausea and vomiting can occur.
After this incident CFS issued a guideline on properly labelling products.


Lack of transparency in the seafood supply chain

Hong Kong imports seafood from between 150 – 170 territories. Much of this seafood does not have even basic labelling as to the species, origin, and production method, and much is not even legally produced.

Unlike meat products, neither an import license nor a health certificate (from the country of origin) is required for seafood imported into Hong Kong.


Source: Guide to Application for Import Licence for Frozen Meat, Chilled Meat, Frozen Poultry and Chilled Poultry,
Guide to Import of Marine Products into HK

What you can do?

All of the above problems stem from the mismanagement of fisheries and aquaculture.

As consumers, you can help by:



Reduce the amount, frequency, and variety of seafood consumption



Choose sustainably caught or farmed seafood

Sustainable seafood is seafood that
has been captured or farmed in a way that:

  • Minimizes harm to the marine environment
  • The population of the target species is not being overfished
  • Comes from well-managed fisheries or farms so that our oceans remain healthy

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